Oops, looks like the latest code didn't get into production today. I'm 
building it again, same plan as before.

On Monday, October 5, 2015 at 4:38:00 PM UTC-7, Dormando wrote:
>
> Looking forward to the results. Thanks for getting on this so quickly. 
>
> I think there's still a bug in tracking requested memory, and I want to 
> move the stats counters to a rollup at the end of a page move. 
> Otherwise I think this branch is complete pending any further stability 
> issues or feedback. 
>
> On Mon, 5 Oct 2015, Scott Mansfield wrote: 
>
> > I just put the newest code into production. I'm going to monitor it for 
> a bit to see how it behaves. As long as there's no obvious issues I'll 
> enable reads in a few hours, which are an order of magnitude more traffic. 
> I'll let you know what I find. 
> > 
> > On Monday, October 5, 2015 at 1:29:03 AM UTC-7, Dormando wrote: 
> >       It took a day of running torture tests which took 30-90 minutes to 
> fail, 
> >       but along with a bunch of house chores I believe I've found the 
> problem: 
> > 
> >       https://github.com/dormando/memcached/tree/slab_rebal_next - has 
> a new 
> >       commit, specifically this: 
> >       
> https://github.com/dormando/memcached/commit/1c32e5eeff5bd2a8cc9b652a2ed808157e4929bb
>  
> > 
> >       It's somewhat relieving that when I brained this super hard back 
> in 
> >       january I may have actually gotten the complex set of interactions 
> >       correct, I simply failed to keep typing when converting the 
> comments to 
> >       code. 
> > 
> >       So this has been broken since 1.4.24, but hardly anyone uses the 
> page 
> >       mover apparently. It's survived a 5 hour torture test (that I 
> wrote in 
> >       2011!) once fixed (previously dying after 30-90 minutes). So 
> please give 
> >       this one a try and let me know how it goes. 
> > 
> >       If it goes well I can merge up some other fixes from PR list and 
> cut a 
> >       release, unless someone has feedback for something to change. 
> > 
> >       thanks! 
> > 
> >       On Thu, 1 Oct 2015, dormando wrote: 
> > 
> >       > I've seen items.c:1183 reported elsewhere in 1.4.24... so 
> probably the bug 
> >       > was introduced when I rewrote the page mover for that. 
> >       > 
> >       > I didn't mean to send me a core file: I mean if you dump the 
> core you can 
> >       > load it in gdb and get the backtrace (bt + thread apply all bt) 
> >       > 
> >       > Don't have a handler for convenient attaching :( 
> >       > 
> >       > didn't get a chance to poke at this today... I'll need another 
> day to try 
> >       > it out. 
> >       > 
> >       > On Thu, 1 Oct 2015, Scott Mansfield wrote: 
> >       > 
> >       > > Sorry for the data dumps here, but I want to give you 
> everything I have. I found 3 more addresses that showed up in the dmesg 
> logs: 
> >       > > 
> >       > > $ for addr in 40e013 40eff4 40f7c4; do addr2line -e memcached 
> $addr; done 
> >       > > 
> >       > > .../build/memcached-1.4.24-slab-rebal-next/slabs.c:265 
> (discriminator 1) 
> >       > > 
> >       > > .../build/memcached-1.4.24-slab-rebal-next/items.c:312 
> (discriminator 1) 
> >       > > 
> >       > > .../build/memcached-1.4.24-slab-rebal-next/items.c:1183 
> >       > > 
> >       > > 
> >       > > I still haven't tried to attach a debugger, since the 
> frequency of the error would make it hard to catch it. Is there a handler 
> that I could add in to dump the stack trace when it segfaults? I'd get a 
> core dump, but they would be HUGE and contain confidential information. 
> >       > > 
> >       > > 
> >       > > Below are the full dmesg logs. Out of 205 servers, 35 had 
> dmesg logs after a memcached crash, and only one crashed twice, both times 
> on the original segfault. Below is the full unified set of dmesg logs, from 
> which you can get a sense of frequency. 
> >       > > 
> >       > > 
> >       > > [47992.109269] memcached[2798]: segfault at 0 ip 
> 000000000040e007 sp 00007f4d20d25eb0 error 4 in memcached[400000+1d000] 
> >       > > 
> >       > > [48960.851278] memcached[2805]: segfault at 0 ip 
> 000000000040e007 sp 00007f3c30d15eb0 error 4 in memcached[400000+1d000] 
> >       > > 
> >       > > [46421.604609] memcached[2784]: segfault at 0 ip 
> 000000000040e007 sp 00007fdb94612eb0 error 4 in memcached[400000+1d000] 
> >       > > 
> >       > > [48429.671534] traps: memcached[2768] general protection 
> ip:40e013 sp:7f1c32676be0 error:0 in memcached[400000+1d000] 
> >       > > 
> >       > > [71838.979269] memcached[2792]: segfault at 0 ip 
> 000000000040e007 sp 00007f0162feeeb0 error 4 in memcached[400000+1d000] 
> >       > > 
> >       > > [66763.091475] memcached[2804]: segfault at 0 ip 
> 000000000040e007 sp 00007f8240170eb0 error 4 in memcached[400000+1d000] 
> >       > > 
> >       > > [102544.376092] traps: memcached[2792] general protection 
> ip:40eff4 sp:7fa58095be18 error:0 in memcached[400000+1d000] 
> >       > > 
> >       > > [49932.757825] memcached[2777]: segfault at 0 ip 
> 000000000040e007 sp 00007f1ff2131eb0 error 4 in memcached[400000+1d000] 
> >       > > 
> >       > > [50400.415878] memcached[2794]: segfault at 0 ip 
> 000000000040e007 sp 00007f11a26daeb0 error 4 in memcached[400000+1d000] 
> >       > > 
> >       > > [48986.340345] memcached[2786]: segfault at 0 ip 
> 000000000040e007 sp 00007f9235279eb0 error 4 in memcached[400000+1d000] 
> >       > > 
> >       > > [44742.175894] memcached[2796]: segfault at 0 ip 
> 000000000040e007 sp 00007eff3a0cceb0 error 4 in memcached[400000+1d000] 
> >       > > 
> >       > > [49030.431879] memcached[2776]: segfault at 0 ip 
> 000000000040e007 sp 00007fdef27cfbe0 error 4 in memcached[400000+1d000] 
> >       > > 
> >       > > [50211.611439] traps: memcached[2782] general protection 
> ip:40e013 sp:7f9ee1723be0 error:0 in memcached[400000+1d000] 
> >       > > 
> >       > > [62534.892817] memcached[2783]: segfault at 0 ip 
> 000000000040e007 sp 00007f37f2d4beb0 error 4 in memcached[400000+1d000] 
> >       > > 
> >       > > [78697.201195] memcached[2801]: segfault at 0 ip 
> 000000000040e007 sp 00007f696ef1feb0 error 4 in memcached[400000+1d000] 
> >       > > 
> >       > > [48922.246712] memcached[2804]: segfault at 0 ip 
> 000000000040e007 sp 00007f1ebb338eb0 error 4 in memcached[400000+1d000] 
> >       > > 
> >       > > [52170.371014] memcached[2809]: segfault at 0 ip 
> 000000000040e007 sp 00007f5e62fcbeb0 error 4 in memcached[400000+1d000] 
> >       > > 
> >       > > [69531.775868] memcached[2785]: segfault at 0 ip 
> 000000000040e007 sp 00007ff50ac2eeb0 error 4 in memcached[400000+1d000] 
> >       > > 
> >       > > [48926.661559] memcached[2799]: segfault at 0 ip 
> 000000000040e007 sp 00007f71e0ac6be0 error 4 in memcached[400000+1d000] 
> >       > > 
> >       > > [49491.126885] memcached[2745]: segfault at 0 ip 
> 000000000040e007 sp 00007f5737c4beb0 error 4 in memcached[400000+1d000] 
> >       > > 
> >       > > [104247.724294] traps: memcached[2793] general protection 
> ip:40f7c4 sp:7f3af8c27eb0 error:0 in memcached[400000+1d000] 
> >       > > 
> >       > > [78098.528606] traps: memcached[2757] general protection 
> ip:412b9d sp:7fc0700dbdd0 error:0 in memcached[400000+1d000] 
> >       > > 
> >       > > [71958.385432] memcached[2809]: segfault at 0 ip 
> 000000000040e007 sp 00007f8b68cd0eb0 error 4 in memcached[400000+1d000] 
> >       > > 
> >       > > [48934.182852] memcached[2787]: segfault at 0 ip 
> 000000000040e007 sp 00007f0aef774eb0 error 4 in memcached[400000+1d000] 
> >       > > 
> >       > > [104220.754195] traps: memcached[2802] general protection 
> ip:40f7c4 sp:7ffa85a2deb0 error:0 in memcached[400000+1d000] 
> >       > > 
> >       > > [45807.670246] memcached[2755]: segfault at 0 ip 
> 000000000040e007 sp 00007fd74a1d0eb0 error 4 in memcached[400000+1d000] 
> >       > > 
> >       > > [73640.102621] memcached[2802]: segfault at 0 ip 
> 000000000040e007 sp 00007f7bb30bfeb0 error 4 in memcached[400000+1d000] 
> >       > > 
> >       > > [67690.640196] memcached[2787]: segfault at 0 ip 
> 000000000040e007 sp 00007f299580feb0 error 4 in memcached[400000+1d000] 
> >       > > 
> >       > > [57729.895442] memcached[2786]: segfault at 0 ip 
> 000000000040e007 sp 00007f204073deb0 error 4 in memcached[400000+1d000] 
> >       > > 
> >       > > [48009.284226] memcached[2801]: segfault at 0 ip 
> 000000000040e007 sp 00007f7b30876eb0 error 4 in memcached[400000+1d000] 
> >       > > 
> >       > > [48198.211826] memcached[2811]: segfault at 0 ip 
> 000000000040e007 sp 00007fd496d79eb0 error 4 in memcached[400000+1d000] 
> >       > > 
> >       > > [84057.439927] traps: memcached[2804] general protection 
> ip:40f7c4 sp:7fbe75fffeb0 error:0 in memcached[400000+1d000] 
> >       > > 
> >       > > [50215.489124] memcached[2784]: segfault at 0 ip 
> 000000000040e007 sp 00007f3234b73eb0 error 4 in memcached[400000+1d000] 
> >       > > 
> >       > > [46545.316351] memcached[2789]: segfault at 0 ip 
> 000000000040e007 sp 00007f362ceedeb0 error 4 in memcached[400000+1d000] 
> >       > > 
> >       > > [102076.523474] memcached[29833]: segfault at 0 ip 
> 000000000040e007 sp 00007f3c89b9ebe0 error 4 in memcached[400000+1d000] 
> >       > > 
> >       > > [55537.568254] memcached[2780]: segfault at 0 ip 
> 000000000040e007 sp 00007fc1f6005eb0 error 4 in memcached[400000+1d000] 
> >       > > 
> >       > > 
> >       > > 
> >       > > 
> >       > > On Thursday, October 1, 2015 at 5:40:35 PM UTC-7, Dormando 
> wrote: 
> >       > >       got it. that might be a decent hint actually... I had 
> addded a bugfix to 
> >       > >       the branch to not miscount the mem_requested counter, 
> but it's not working 
> >       > >       or I missed a spot. 
> >       > > 
> >       > >       On Thu, 1 Oct 2015, Scott Mansfield wrote: 
> >       > > 
> >       > >       > The number now, after maybe 90 minutes of writes, 
> is 1,446. I think after disabling a lot of the data TTL'd out. I have to 
> disable it for now, again (for unrelated reasons, again). The page that I 
> screenshotted gives real time data, so the numbers were from right then. 
> Last night, it should have shown better numbers in terms of 
> >       "total_pages", 
> >       > >       but I didn't 
> >       > >       > get a screenshot. That number is directly from the 
> stats slabs output. 
> >       > >       > 
> >       > >       > 
> >       > >       > 
> >       > >       > On Thursday, October 1, 2015 at 4:21:42 PM UTC-7, 
> Dormando wrote: 
> >       > >       >       ok... slab class 12 claims to have 2 in 
> "total_pages", yet 14g in 
> >       > >       >       mem_requested. is this stat wrong? 
> >       > >       > 
> >       > >       >       On Thu, 1 Oct 2015, Scott Mansfield wrote: 
> >       > >       > 
> >       > >       >       > The ones that crashed (new code cluster) were 
> set to only be written to from the client applications. The data is an 
> index key and a series of data keys that are all written one after another. 
> Each key might be hashed to a different server, though, so not all of them 
> are written to the same server. I can give you a snapshot 
> >       of one of 
> >       > >       the 
> >       > >       >       clusters that 
> >       > >       >       > didn't crash (attached file). I can give more 
> detail offline if you need it. 
> >       > >       >       > 
> >       > >       >       > 
> >       > >       >       > On Thursday, October 1, 2015 at 2:32:53 PM 
> UTC-7, Dormando wrote: 
> >       > >       >       >       Any chance you could describe (perhaps 
> privately?) in very broad strokes 
> >       > >       >       >       what the write load looks like? (they're 
> getting only writes, too?). 
> >       > >       >       >       otherwise I'll have to devise arbitrary 
> torture tests. I'm sure the bug's 
> >       > >       >       >       in there but it's not obvious yet 
> >       > >       >       > 
> >       > >       >       >       On Thu, 1 Oct 2015, dormando wrote: 
> >       > >       >       > 
> >       > >       >       >       > perfect, thanks! I have $dayjob as 
> well but will look into this as soon as 
> >       > >       >       >       > I can. my torture test machines are in 
> a box but I'll try to borrow one 
> >       > >       >       >       > 
> >       > >       >       >       > On Thu, 1 Oct 2015, Scott Mansfield 
> wrote: 
> >       > >       >       >       > 
> >       > >       >       >       > > Yes. Exact args: 
> >       > >       >       >       > > -p 11211 -u <omitted> -l 0.0.0.0 -c 
> 100000 -o slab_reassign -o 
> lru_maintainer,lru_crawler,hash_algorithm=murmur3 -I 4m -m 56253 
> >       > >       >       >       > > 
> >       > >       >       >       > > On Thursday, October 1, 2015 at 
> 12:41:06 PM UTC-7, Dormando wrote: 
> >       > >       >       >       > >       Were 
> lru_maintainer/lru_crawler/etc enabled though? even if slab mover is 
> >       > >       >       >       > >       off, those two were the big 
> changes in .24 
> >       > >       >       >       > > 
> >       > >       >       >       > >       On Thu, 1 Oct 2015, Scott 
> Mansfield wrote: 
> >       > >       >       >       > > 
> >       > >       >       >       > >       > The same cluster has > 400 
> servers happily running 1.4.24. It's been our standard deployment for a 
> while now, and we haven't seen any crashes. The servers in the same cluster 
> running 1.4.24 (with the same write load the new build was taking) have 
> been up for 29 days. The start options do not contain the 
> >       slab_automove 
> >       > >       option 
> >       > >       >       because 
> >       > >       >       >       it wasn't 
> >       > >       >       >       > >       effective for 
> >       > >       >       >       > >       > us before. The memory given 
> is possibly slightly different per server, as we calculate on startup how 
> much we give. It's in the same ballpark, though (~56 gigs). 
> >       > >       >       >       > >       > 
> >       > >       >       >       > >       > On Thursday, October 1, 2015 
> at 12:11:35 PM UTC-7, Dormando wrote: 
> >       > >       >       >       > >       >       Just before I sit in 
> and try to narrow this down: have you run any host on 
> >       > >       >       >       > >       >       1.4.24 mainline with 
> those same start options? just in case the crash is 
> >       > >       >       >       > >       >       older 
> >       > >       >       >       > >       > 
> >       > >       >       >       > >       >       On Thu, 1 Oct 2015, 
> Scott Mansfield wrote: 
> >       > >       >       >       > >       > 
> >       > >       >       >       > >       >       > Another message for 
> you: 
> >       > >       >       >       > >       >       > [78098.528606] 
> traps: memcached[2757] general protection ip:412b9d sp:7fc0700dbdd0 error:0 
> in memcached[400000+1d000] 
> >       > >       >       >       > >       >       > 
> >       > >       >       >       > >       >       > 
> >       > >       >       >       > >       >       > addr2line shows: 
> >       > >       >       >       > >       >       > 
> >       > >       >       >       > >       >       > $ addr2line -e 
> memcached 412b9d 
> >       > >       >       >       > >       >       > 
> >       > >       >       >       > >       >       > 
> /mnt/builds/slave/workspace/TL-SYS-memcached-slab_rebal_next/build/memcached-1.4.24-slab-rebal-next/assoc.c:119
>  
>
> >       > >       >       >       > >       >       > 
> >       > >       >       >       > >       >       > 
> >       > >       >       >       > >       >       > 
> >       > >       >       >       > >       >       > On Thursday, October 
> 1, 2015 at 1:41:44 AM UTC-7, Dormando wrote: 
> >       > >       >       >       > >       >       >       Ok, thanks! 
> >       > >       >       >       > >       >       > 
> >       > >       >       >       > >       >       >       I'll noodle 
> this a bit... unfortunately a backtrace might be more helpful. 
> >       > >       >       >       > >       >       >       will ask you 
> to attempt to get one if I don't figure anything out in time. 
> >       > >       >       >       > >       >       > 
> >       > >       >       >       > >       >       >       (allow it to 
> core dump or attach a GDB session and set an ignore handler 
> >       > >       >       >       > >       >       >       for 
> sigpipe/int/etc and run "continue") 
> >       > >       >       >       > >       >       > 
> >       > >       >       >       > >       >       >       what were your 
> full startup args, though? 
> >       > >       >       >       > >       >       > 
> >       > >       >       >       > >       >       >       On Thu, 1 Oct 
> 2015, Scott Mansfield wrote: 
> >       > >       >       >       > >       >       > 
> >       > >       >       >       > >       >       >       > The commit 
> was the latest in slab_rebal_next at the time: 
> >       > >       >       >       > >       >       >       > 
> https://github.com/dormando/memcached/commit/bdd688b4f20120ad844c8a4803e08c6e03cb061a
>  
> >       > >       >       >       > >       >       >       > 
> >       > >       >       >       > >       >       >       > addr2line 
> gave me this output: 
> >       > >       >       >       > >       >       >       > 
> >       > >       >       >       > >       >       >       > $ addr2line 
> -e memcached 0x40e007 
> >       > >       >       >       > >       >       >       > 
> >       > >       >       >       > >       >       >       > 
> /mnt/builds/slave/workspace/TL-SYS-memcached-slab_rebal_next/build/memcached-1.4.24-slab-rebal-next/slabs.c:264
>  
>
> >       > >       >       >       > >       >       >       > 
> >       > >       >       >       > >       >       >       > 
> >       > >       >       >       > >       >       >       > As well, 
> this was running with production writes, but not reads. Even if we had 
> reads on with the few servers crashing, we're ok architecturally. That's 
> why I can get it out there without worrying too much. For now, I'm going to 
> turn it off. I had a metrics issue anyway that needs to get 
> >       fixed. 
> >       > >       Tomorrow I'm 
> >       > >       >       planning 
> >       > >       >       >       to test 
> >       > >       >       >       > >       again with 
> >       > >       >       >       > >       >       more 
> >       > >       >       >       > >       >       >       metrics, but I 
> >       > >       >       >       > >       >       >       > can get any 
> new code in pretty quick. 
> >       > >       >       >       > >       >       >       > 
> >       > >       >       >       > >       >       >       > 
> >       > >       >       >       > >       >       >       > On Thursday, 
> October 1, 2015 at 1:01:36 AM UTC-7, Dormando wrote: 
> >       > >       >       >       > >       >       >       >       How 
> many servers were you running it on? I hope it wasn't more than a 
> >       > >       >       >       > >       >       >       >       
> handful. I'd recommend starting with one :P 
> >       > >       >       >       > >       >       >       > 
> >       > >       >       >       > >       >       >       >       can 
> you do an addr2line? what were your startup args, and what was the 
> >       > >       >       >       > >       >       >       >       commit 
> sha1 for the branch you pulled? 
> >       > >       >       >       > >       >       >       > 
> >       > >       >       >       > >       >       >       >       sorry 
> about that :/ 
> >       > >       >       >       > >       >       >       > 
> >       > >       >       >       > >       >       >       >       On 
> Thu, 1 Oct 2015, Scott Mansfield wrote: 
> >       > >       >       >       > >       >       >       > 
> >       > >       >       >       > >       >       >       >       > A 
> few different servers (5 / 205) experienced a segfault all within an hour 
> or so. Unfortunately at this point I'm a bit out of my depth. I have the 
> dmesg output, which is identical for all 5 boxes: 
> >       > >       >       >       > >       >       >       >       > 
> >       > >       >       >       > >       >       >       >       > 
> [46545.316351] memcached[2789]: segfault at 0 ip 000000000040e007 sp 
> 00007f362ceedeb0 error 4 in memcached[400000+1d000] 
> >       > >       >       >       > >       >       >       >       > 
> >       > >       >       >       > >       >       >       >       > 
> >       > >       >       >       > >       >       >       >       > I 
> can possibly supply the binary file if needed, though we didn't do anything 
> besides the standard setup and compile. 
> >       > >       >       >       > >       >       >       >       > 
> >       > >       >       >       > >       >       >       >       > 
> >       > >       >       >       > >       >       >       >       > 
> >       > >       >       >       > >       >       >       >       > On 
> Tuesday, September 29, 2015 at 10:27:59 PM UTC-7, Dormando wrote: 
> >       > >       >       >       > >       >       >       >       >     
>   If you look at the new branch there's a commit explaining the new stats. 
> >       > >       >       >       > >       >       >       >       > 
> >       > >       >       >       > >       >       >       >       >     
>   You can watch slab_reassing_evictions vs slab_reassign_saves. you can 
> also 
> >       > >       >       >       > >       >       >       >       >     
>   test automove=1 vs automove=2 (please also turn on the lru_maintainer and 
> >       > >       >       >       > >       >       >       >       >     
>   lru_crawler). 
> >       > >       >       >       > >       >       >       >       > 
> >       > >       >       >       > >       >       >       >       >     
>   The initial branch you were running didn't add any new stats. It just 
> >       > >       >       >       > >       >       >       >       >     
>   restored an old feature. 
> >       > >       >       >       > >       >       >       >       > 
> >       > >       >       >       > >       >       >       >       >     
>   On Tue, 29 Sep 2015, Scott Mansfield wrote: 
> >       > >       >       >       > >       >       >       >       > 
> >       > >       >       >       > >       >       >       >       >     
>   > An unrelated prod problem meant I had to stop after about an hour. I'm 
> turning it on again tomorrow morning. 
> >       > >       >       >       > >       >       >       >       >     
>   > Are there any new metrics I should be looking at? Anything new in the 
> stats output? I'm about to take a look at the diffs as well. 
> >       > >       >       >       > >       >       >       >       >     
>   > 
> >       > >       >       >       > >       >       >       >       >     
>   > On Tuesday, September 29, 2015 at 12:37:45 PM UTC-7, Dormando wrote: 
> >       > >       >       >       > >       >       >       >       >     
>   >       excellent. if automove=2 is too aggressive you'll see that come 
> in in a 
> >       > >       >       >       > >       >       >       >       >     
>   >       hit ratio reduction. 
> >       > >       >       >       > >       >       >       >       >     
>   > 
> >       > >       >       >       > >       >       >       >       >     
>   >       the new branch works with automove=2 as well, but it will attempt 
> to 
> >       > >       >       >       > >       >       >       >       >     
>   >       rescue valid items in the old slab if possible. I'll still be 
> working on 
> >       > >       >       >       > >       >       >       >       >     
>   >       it for another few hours today though. I'll mail again when I'm 
> done. 
> >       > >       >       >       > >       >       >       >       >     
>   > 
> >       > >       >       >       > >       >       >       >       >     
>   >       On Tue, 29 Sep 2015, Scott Mansfield wrote: 
> >       > >       >       >       > >       >       >       >       >     
>   > 
> >       > >       >       >       > >       >       >       >       >     
>   >       > I have the first commit (slab_automove=2) running in prod right 
> now. Later today will be a full load production test of the latest code. 
> I'll just let it run for a few days unless I spot any problems. We have 
> good metrics for latency et. al. from the client side, 
> >       though network 
> >       > >       normally 
> >       > >       >       dwarfs 
> >       > >       >       >       memcached 
> >       > >       >       >       > >       time. 
> >       > >       >       >       > >       >       >       >       >     
>   >       > 
> >       > >       >       >       > >       >       >       >       >     
>   >       > On Tuesday, September 29, 2015 at 3:10:03 AM UTC-7, Dormando 
> wrote: 
> >       > >       >       >       > >       >       >       >       >     
>   >       >       That's unfortunate. 
> >       > >       >       >       > >       >       >       >       >     
>   >       > 
> >       > >       >       >       > >       >       >       >       >     
>   >       >       I've done some more work on the branch: 
> >       > >       >       >       > >       >       >       >       >     
>   >       >       https://github.com/memcached/memcached/pull/112 
> >       > >       >       >       > >       >       >       >       >     
>   >       > 
> >       > >       >       >       > >       >       >       >       >     
>   >       >       It's not completely likely you would see enough of an 
> improvement from the 
> >       > >       >       >       > >       >       >       >       >     
>   >       >       new default mode. However if your item sizes change 
> gradually, items are 
> >       > >       >       >       > >       >       >       >       >     
>   >       >       reclaimed during expiration, or get overwritten (and thus 
> freed in the old 
> >       > >       >       >       > >       >       >       >       >     
>   >       >       class), it should work just fine. I have another patch 
> coming which should 
> >       > >       >       >       > >       >       >       >       >     
>   >       >       help though. 
> >       > >       >       >       > >       >       >       >       >     
>   >       > 
> >       > >       >       >       > >       >       >       >       >     
>   >       >       Open to feedback from any interested party. 
> >       > >       >       >       > >       >       >       >       >     
>   >       > 
> >       > >       >       >       > >       >       >       >       >     
>   >       >       On Fri, 25 Sep 2015, Scott Mansfield wrote: 
> >       > >       >       >       > >       >       >       >       >     
>   >       > 
> >       > >       >       >       > >       >       >       >       >     
>   >       >       > I have it running internally, and it runs fine under 
> normal load. It's difficult to put it into the line of fire for a 
> production workload because of social reasons... As well it's a degenerate 
> case that we normally don't run in to (and actively try to avoid). 
> >       I'm going 
> >       > >       to run 
> >       > >       >       some 
> >       > >       >       >       heavier load 
> >       > >       >       >       > >       tests on 
> >       > >       >       >       > >       >       it 
> >       > >       >       >       > >       >       >       today.  
> >       > >       >       >       > >       >       >       >       >     
>   >       >       > 
> >       > >       >       >       > >       >       >       >       >     
>   >       >       > On Wednesday, September 9, 2015 at 10:23:32 AM UTC-7, 
> Scott Mansfield wrote: 
> >       > >       >       >       > >       >       >       >       >     
>   >       >       >       I'm working on getting a test going internally. 
> I'll let you know how it goes.  
> >       > >       >       >       > >       >       >       >       >     
>   >       >       > 
> >       > >       >       >       > >       >       >       >       >     
>   >       >       > 
> >       > >       >       >       > >       >       >       >       >     
>   >       >       > Scott Mansfield 
> >       > >       >       >       > >       >       >       >       >     
>   >       >       > On Mon, Sep 7, 2015 at 2:33 PM, dormando wrote: 
> >       > >       >       >       > >       >       >       >       >     
>   >       >       >       Yo, 
> >       > >       >       >       > >       >       >       >       >     
>   >       >       > 
> >       > >       >       >       > >       >       >       >       >     
>   >       >       >       
> https://github.com/dormando/memcached/commits/slab_rebal_next - would you 
> >       > >       >       >       > >       >       >       >       >     
>   >       >       >       mind playing around with the branch here? You can 
> see the start options in 
> >       > >       >       >       > >       >       >       >       >     
>   >       >       >       the test. 
> >       > >       >       >       > >       >       >       >       >     
>   >       >       > 
> >       > >       >       >       > >       >       >       >       >     
>   >       >       >       This is a dead simple modification (a restoration 
> of a feature that was 
> >       > >       >       >       > >       >       >       >       >     
>   >       >       >       arleady there...). The test very aggressively 
> writes and is able to shunt 
> >       > >       >       >       > >       >       >       >       >     
>   >       >       >       memory around appropriately. 
> >       > >       >       >       > >       >       >       >       >     
>   >       >       > 
> >       > >       >       >       > >       >       >       >       >     
>   >       >       >       The work I'm exploring right now will allow 
> savings of items being 
> >       > >       >       >       > >       >       >       >       >     
>   >       >       >       rebalanced from, and increasing the aggression of 
> page moving without 
> >       > >       >       >       > >       >       >       >       >     
>   >       >       >       being so brain damaged about it. 
> >       > >       >       >       > >       >       >       >       >     
>   >       >       > 
> >       > >       >       >       > >       >       >       >       >     
>   >       >       >       But while I'm poking around with that, I'd be 
> interested in knowing if 
> >       > >       >       >       > >       >       >       >       >     
>   >       >       >       this simple branch is an improvement, and if so 
> how much. 
> >       > >       >       >       > >       >       >       >       >     
>   >       >       > 
> >       > >       >       >       > >       >       >       >       >     
>   >       >       >       I'll push more code to the branch, but the 
> changes should be gated behind 
> >       > >       >       >       > >       >       >       >       >     
>   >       >       >       a feature flag. 
> >       > >       >       >       > >       >       >       >       >     
>   >       >       > 
> >       > >       >       >       > >       >       >       >       >     
>   >       >       >       On Tue, 18 Aug 2015, 'Scott Mansfield' via 
> memcached wrote: 
> >       > >       >       >       > >       >       >       >       >     
>   >       >       > 
> >       > >       >       >       > >       >       >       >       >     
>   >       >       >       > 
> >       > >       >       >       > >       >       >       >       >     
>   >       >       >       > No worries man, you're doing us a favor. Let me 
> know if there's anything you need from us, and I promise I'll be quicker 
> this time :) 
> >       > >       >       >       > >       >       >       >       >     
>   >       >       >       > 
> >       > >       >       >       > >       >       >       >       >     
>   >       >       >       > On Aug 18, 2015 12:01 AM, "dormando" <
> dorm...@rydia.net> wrote: 
> >       > >       >       >       > >       >       >       >       >     
>   >       >       >       >       Hey, 
> >       > >       >       >       > >       >       >       >       >     
>   >       >       >       > 
> >       > >       >       >       > >       >       >       >       >     
>   >       >       >       >       I'm still really interested in working on 
> this. I'll be taking a careful 
> >       > >       >       >       > >       >       >       >       >     
>   >       >       >       >       look soon I hope. 
> >       > >       >       >       > >       >       >       >       >     
>   >       >       >       > 
> >       > >       >       >       > >       >       >       >       >     
>   >       >       >       >       On Mon, 3 Aug 2015, Scott Mansfield 
> wrote: 
> >       > >       >       >       > >       >       >       >       >     
>   >       >       >       > 
> >       > >       >       >       > >       >       >       >       >     
>   >       >       >       >       > I've tweaked the program slightly, so 
> I'm adding a new version. It prints more stats as it goes and runs a bit 
> faster. 
> >       > >       >       >       > >       >       >       >       >     
>   >       >       >       >       > 
> >       > >       >       >       > >       >       >       >       >     
>   >       >       >       >       > On Monday, August 3, 2015 at 1:20:37 AM 
> UTC-7, Scott Mansfield wrote: 
> >       > >       >       >       > >       >       >       >       >     
>   >       >       >       >       >       Total brain fart on my part. 
> Apparently I had memcached 1.4.13 on my path (who knows how...) Using the 
> actual one that I've built works. Sorry for the confusion... can't believe 
> I didn't realize that before. I'm testing against the 
> >       compiled one now 
> >       > >       to see 
> >       > >       >       how it 
> >       > >       >       >       behaves. 
> >       > >       >       >       > >       >       >       >       >     
>   >       >       >       >       >       On Monday, August 3, 2015 at 
> 1:15:06 AM UTC-7, Dormando wrote: 
> >       > >       >       >       > >       >       >       >       >     
>   >       >       >       >       >             You sure that's 1.4.24? 
> None of those fail for me :( 
> >       > >       >       >       > >       >       >       >       >     
>   >       >       >       >       > 
> >       > >       >       >       > >       >       >       >       >     
>   >       >       >       >       >             On Mon, 3 Aug 2015, Scott 
> Mansfield wrote: 
> >       > >       >       >       > >       >       >       >       >     
>   >       >       >       >       > 
> >       > >       >       >       > >       >       >       >       >     
>   >       >       >       >       >             > The command line I've 
> used that will start is: 
> >       > >       >       >       > >       >       >       >       >     
>   >       >       >       >       >             > 
> >       > >       >       >       > >       >       >       >       >     
>   >       >       >       >       >             > memcached -m 64 -o 
> slab_reassign,slab_automove 
> >       > >       >       >       > >       >       >       >       >     
>   >       >       >       >       >             > 
> >       > >       >       >       > >       >       >       >       >     
>   >       >       >       >       >             > 
> >       > >       >       >       > >       >       >       >       >     
>   >       >       >       >       >             > the ones that fail are: 
> >       > >       >       >       > >       >       >       >       >     
>   >       >       >       >       >             > 
> >       > >       >       >       > >       >       >       >       >     
>   >       >       >       >       >             > 
> >       > >       >       >       > >       >       >       >       >     
>   >       >       >       >       >             > memcached -m 64 -o 
> slab_reassign,slab_automove,lru_crawler,lru_maintainer 
> >       > >       >       >       > >       >       >       >       >     
>   >       >       >       >       >             > 
> >       > >       >       >       > >       >       >       >       >     
>   >       >       >       >       >             > memcached -o lru_crawler 
> >       > >       >       >       > >       >       >       >       >     
>   >       >       >       >       >             > 
> >       > >       >       >       > >       >       >       >       >     
>   >       >       >       >       >             > 
> >       > >       >       >       > >       >       >       >       >     
>   >       >       >       >       >             > I'm sure I've missed 
> something during compile, though I just used ./configure and make. 
> >       > >       >       >       > >       >       >       >       >     
>   >       >       >       >       >             > 
> >       > >       >       >       > >       >       >       >       >     
>   >       >       >       >       >             > 
> >       > >       >       >       > >       >       >       >       >     
>   >       >       >       >       >             > On Monday, August 3, 2015 
> at 12:22:33 AM UTC-7, Scott Mansfield wrote: 
> >       > >       >       >       > >       >       >       >       >     
>   >       >       >       >       >             >       I've attached a 
> pretty simple program to connect, fill a slab with data, and then fill 
> another slab slowly with data of a different size. I've been trying to get 
> memcached to run with the lru_crawler and lru_maintainer flags, 
> >       but I get 
> >       > >       ' 
> >       > >       >       >       > >       >       >       >       >     
>   >       >       >       >       >             > 
> >       > >       >       >       > >       >       >       >       >     
>   >       >       >       >       >             >       Illegal suboption 
> "(null)"' every time I try to start with either in any configuration. 
> >       > >       >       >       > >       >       >       >       >     
>   >       >       >       >       >             > 
> >       > >       >       >       > >       >       >       >       >     
>   >       >       >       >       >             > 
> >       > >       >       >       > >       >       >       >       >     
>   >       >       >       >       >             >       I haven't seen it 
> start to move slabs automatically with a freshly installed 1.2.24. 
> >       > >       >       >       > >       >       >       >       >     
>   >       >       >       >       >             > 
> >       > >       >       >       > >       >       >       >       >     
>   >       >       >       >       >             > 
> >       > >       >       >       > >       >       >       >       >     
>   >       >       >       >       >             >       On Tuesday, July 
> 21, 2015 at 4:55:17 PM UTC-7, Scott Mansfield wrote: 
> >       > >       >       >       > >       >       >       >       >     
>   >       >       >       >       >             >             I realize 
> I've not given you the tests to reproduce the behavior. I should be able to 
> soon. Sorry about the delay here. 
> >       > >       >       >       > >       >       >       >       >     
>   >       >       >       >       >             > In the mean time, I 
> wanted to bring up a possible secondary use of the same logic to move items 
> on slab rebalancing. I think the system might benefit from using the same 
> logic to crawl the pages in a slab and compact the data in 
> >       the 
> >       > >       background. In 
> >       > >       >       the case 
> >       > >       >       >       where we 
> >       > >       >       >       > >       have 
> >       > >       >       >       > >       >       memory that 
> >       > >       >       >       > >       >       >       is 
> >       > >       >       >       > >       >       >       >       
> assigned to 
> >       > >       >       >       > >       >       >       >       >     
>   the slab 
> >       > >       >       >       > >       >       >       >       >     
>   >       but not 
> >       > >       >       >       > >       >       >       >       >     
>   >       >       >       being used 
> >       > >       >       >       > >       >       >       >       >     
>   >       >       >       >       because 
> >       > >       >       >       > >       >       >       >       >     
>   >       >       >       >       >             of replaced 
> >       > >       >       >       > >       >       >       >       >     
>   >       >       >       >       >             > or TTL'd out data, 
> returning the memory to a pool of free memory will allow a slab to grow 
> with that memory first instead of waiting for an event where memory is 
> needed at that instant. 
> >       > >       >       >       > >       >       >       >       >     
>   >       >       >       >       >             > 
> >       > >       >       >       > >       >       >       >       >     
>   >       >       >       >       >             > It's a change in 
> approach, from reactive to proactive. What do you think? 
> >       > >       >       >       > >       >       >       >       >     
>   >       >       >       >       >     ...

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