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? > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > On Monday, July 13, 2015 at > 5:54:11 PM UTC-7, Dormando wrote: > > > > > > > > > > > > > > > > > > > First, more detail for > you: > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > We are running 1.4.24 in > production and haven't noticed any bugs as of yet. The new LRUs seem to be > working well, though we nearly always run memcached scaled to hold all data > without evictions. Those with evictions are > behaving > > > well. Those > > > > without > > > > > evictions > > > > > > > haven't > > > > > > > > seen > > > > > > > > > crashing or > > > > > > > > > > any > > > > > > > > > > > > other > > > > > > > > > > > > > noticeable > > > > > > > > > > > > > > bad > > > > > > > > > > > > > > > behavior. > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > Neat. > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > OK, I think I see an area > where I was speculating on functionality. If you have a key in slab 21 and > then the same key is written again at a larger size in slab 23 I assumed that > the space in 21 was not freed on the second > write. > > > With that > > > > > assumption, the LRU > > > > > > > crawler > > > > > > > > would > > > > > > > > > not free > > > > > > > > > > up that > > > > > > > > > > > > space. > > > > > > > > > > > > > Also just > > > > > > > > > > > > > > > by observation > > > > > > > > > > > > > > > > in > > > > > > > > > > > > > > > > > the > > > > > > > > > > > > > > > > > > macro, the space is not > freed > > > > > > > > > > > > > > > > > > > fast enough to be > effective, in our use case, to accept the writes that are happening. Think in > the hundreds of millions of "overwrites" in a 6 - 10 hour period across a > cluster. > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > Internally, "items" (a > key/value pair) are generally immutable. The only > > > > > > > > > > > ... > > -- > > --- > You received this message because you are subscribed to the Google Groups > "memcached" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to memcached+unsubscr...@googlegroups.com. > For more options, visit https://groups.google.com/d/optout. > >
