Re: ZFS txg implementation flaw
On Mon, Oct 28, 2013 at 02:56:17PM -0700, Xin Li wrote:
> >>> Semi-indirect. dtrace -n 'fbt:kernel:vm_object_terminate:entry
> >>> { @traces[stack()] = count(); }'
> >>>
> >>> After some (2-3) seconds
> >>>
> >>> kernel`vnode_destroy_vobject+0xb9
> >>> zfs.ko`zfs_freebsd_reclaim+0x2e kernel`VOP_RECLAIM_APV+0x78
> >>> kernel`vgonel+0x134 kernel`vnlru_free+0x362
> >>> kernel`vnlru_proc+0x61e kernel`fork_exit+0x11f
> >>> kernel`0x80cdbfde 2490
> >
> > 0x80cdbfd0 : mov%r12,%rdi
> > 0x80cdbfd3 : mov%rbx,%rsi
> > 0x80cdbfd6 : mov%rsp,%rdx
> > 0x80cdbfd9 : callq 0x808db560
> > 0x80cdbfde :jmpq
> > 0x80cdca80 0x80cdbfe3
> > :nopw 0x0(%rax,%rax,1)
> > 0x80cdbfe9 :nopl 0x0(%rax)
> >
> >
> >>> I don't have user process created threads nor do fork/exit.
> >>
> >> This has nothing to do with fork/exit but does suggest that you
> >> are running of vnodes. What does sysctl -a | grep vnode say?
> >
> > kern.maxvnodes: 1095872 kern.minvnodes: 273968
> > vm.stats.vm.v_vnodepgsout: 0 vm.stats.vm.v_vnodepgsin: 62399
> > vm.stats.vm.v_vnodeout: 0 vm.stats.vm.v_vnodein: 10680
> > vfs.freevnodes: 275107 vfs.wantfreevnodes: 273968 vfs.numvnodes:
> > 316321 debug.sizeof.vnode: 504
>
> Try setting vfs.wantfreevnodes to 547936 (double it).
Now fork_trampoline was gone, but I still see prcfr (and zfod/totfr
too). Currently half of peeak traffic and I can't check impact to IRQ
handling.
kern.maxvnodes: 1095872
kern.minvnodes: 547936
vm.stats.vm.v_vnodepgsout: 0
vm.stats.vm.v_vnodepgsin: 63134
vm.stats.vm.v_vnodeout: 0
vm.stats.vm.v_vnodein: 10836
vfs.freevnodes: 481873
vfs.wantfreevnodes: 547936
vfs.numvnodes: 517331
debug.sizeof.vnode: 504
Now dtrace -n 'fbt:kernel:vm_object_terminate:entry { @traces[stack()] =
count(); }'
kernel`vm_object_deallocate+0x520
kernel`vm_map_entry_deallocate+0x4c
kernel`vm_map_process_deferred+0x3d
kernel`sys_munmap+0x16c
kernel`amd64_syscall+0x5ea
kernel`0x80cdbd97
56
I think this is nginx memory management (allocation|dealocation). Can
I tune malloc to disable free pages?
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Re: ZFS txg implementation flaw
On Oct 28, 2013, at 2:28 AM, Slawa Olhovchenkov wrote: > As I see ZFS cretate seperate thread for earch txg writing. > Also for writing to L2ARC. > As result -- up to several thousands threads created and destoyed per > second. And hundreds thousands page allocations, zeroing, maping > unmaping and freeing per seconds. Very high overhead. How are you measuring the number of threads being created / destroyed? This claim seems erroneous given how the ZFS thread pool mechanism actually works (and yes, there are thread pools already). It would be helpful to both see your measurement methodology and the workload you are using in your tests. - Jordan ___ freebsd-current@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-current To unsubscribe, send any mail to "freebsd-current-unsubscr...@freebsd.org"
Re: ZFS txg implementation flaw
-BEGIN PGP SIGNED MESSAGE-
Hash: SHA512
On 10/28/13 14:45, Slawa Olhovchenkov wrote:
> On Mon, Oct 28, 2013 at 02:38:30PM -0700, Xin Li wrote:
>
>> -BEGIN PGP SIGNED MESSAGE- Hash: SHA512
>>
>> On 10/28/13 14:32, Slawa Olhovchenkov wrote:
>>> On Mon, Oct 28, 2013 at 02:22:16PM -0700, Jordan Hubbard
>>> wrote:
>>>
On Oct 28, 2013, at 2:28 AM, Slawa Olhovchenkov
wrote:
> As I see ZFS cretate seperate thread for earch txg writing.
> Also for writing to L2ARC. As result -- up to several
> thousands threads created and destoyed per second. And
> hundreds thousands page allocations, zeroing, maping
> unmaping and freeing per seconds. Very high overhead.
How are you measuring the number of threads being created /
destroyed? This claim seems erroneous given how the ZFS
thread pool mechanism actually works (and yes, there are
thread pools already).
It would be helpful to both see your measurement methodology
and the workload you are using in your tests.
>>>
>>> Semi-indirect. dtrace -n 'fbt:kernel:vm_object_terminate:entry
>>> { @traces[stack()] = count(); }'
>>>
>>> After some (2-3) seconds
>>>
>>> kernel`vnode_destroy_vobject+0xb9
>>> zfs.ko`zfs_freebsd_reclaim+0x2e kernel`VOP_RECLAIM_APV+0x78
>>> kernel`vgonel+0x134 kernel`vnlru_free+0x362
>>> kernel`vnlru_proc+0x61e kernel`fork_exit+0x11f
>>> kernel`0x80cdbfde 2490
>
> 0x80cdbfd0 : mov%r12,%rdi
> 0x80cdbfd3 : mov%rbx,%rsi
> 0x80cdbfd6 : mov%rsp,%rdx
> 0x80cdbfd9 : callq 0x808db560
> 0x80cdbfde :jmpq
> 0x80cdca80 0x80cdbfe3
> :nopw 0x0(%rax,%rax,1)
> 0x80cdbfe9 :nopl 0x0(%rax)
>
>
>>> I don't have user process created threads nor do fork/exit.
>>
>> This has nothing to do with fork/exit but does suggest that you
>> are running of vnodes. What does sysctl -a | grep vnode say?
>
> kern.maxvnodes: 1095872 kern.minvnodes: 273968
> vm.stats.vm.v_vnodepgsout: 0 vm.stats.vm.v_vnodepgsin: 62399
> vm.stats.vm.v_vnodeout: 0 vm.stats.vm.v_vnodein: 10680
> vfs.freevnodes: 275107 vfs.wantfreevnodes: 273968 vfs.numvnodes:
> 316321 debug.sizeof.vnode: 504
Try setting vfs.wantfreevnodes to 547936 (double it).
Cheers,
- --
Xin LI https://www.delphij.net/
FreeBSD - The Power to Serve! Live free or die
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Re: ZFS txg implementation flaw
On Mon, Oct 28, 2013 at 02:38:30PM -0700, Xin Li wrote:
> -BEGIN PGP SIGNED MESSAGE-
> Hash: SHA512
>
> On 10/28/13 14:32, Slawa Olhovchenkov wrote:
> > On Mon, Oct 28, 2013 at 02:22:16PM -0700, Jordan Hubbard wrote:
> >
> >>
> >> On Oct 28, 2013, at 2:28 AM, Slawa Olhovchenkov
> >> wrote:
> >>
> >>> As I see ZFS cretate seperate thread for earch txg writing.
> >>> Also for writing to L2ARC. As result -- up to several thousands
> >>> threads created and destoyed per second. And hundreds thousands
> >>> page allocations, zeroing, maping unmaping and freeing per
> >>> seconds. Very high overhead.
> >>
> >> How are you measuring the number of threads being created /
> >> destroyed? This claim seems erroneous given how the ZFS thread
> >> pool mechanism actually works (and yes, there are thread pools
> >> already).
> >>
> >> It would be helpful to both see your measurement methodology and
> >> the workload you are using in your tests.
> >
> > Semi-indirect. dtrace -n 'fbt:kernel:vm_object_terminate:entry {
> > @traces[stack()] = count(); }'
> >
> > After some (2-3) seconds
> >
> > kernel`vnode_destroy_vobject+0xb9 zfs.ko`zfs_freebsd_reclaim+0x2e
> > kernel`VOP_RECLAIM_APV+0x78 kernel`vgonel+0x134
> > kernel`vnlru_free+0x362 kernel`vnlru_proc+0x61e
> > kernel`fork_exit+0x11f kernel`0x80cdbfde 2490
0x80cdbfd0 : mov%r12,%rdi
0x80cdbfd3 : mov%rbx,%rsi
0x80cdbfd6 : mov%rsp,%rdx
0x80cdbfd9 : callq 0x808db560
0x80cdbfde :jmpq 0x80cdca80
0x80cdbfe3 :nopw 0x0(%rax,%rax,1)
0x80cdbfe9 :nopl 0x0(%rax)
> > I don't have user process created threads nor do fork/exit.
>
> This has nothing to do with fork/exit but does suggest that you are
> running of vnodes. What does sysctl -a | grep vnode say?
kern.maxvnodes: 1095872
kern.minvnodes: 273968
vm.stats.vm.v_vnodepgsout: 0
vm.stats.vm.v_vnodepgsin: 62399
vm.stats.vm.v_vnodeout: 0
vm.stats.vm.v_vnodein: 10680
vfs.freevnodes: 275107
vfs.wantfreevnodes: 273968
vfs.numvnodes: 316321
debug.sizeof.vnode: 504
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Re: ZFS txg implementation flaw
-BEGIN PGP SIGNED MESSAGE-
Hash: SHA512
On 10/28/13 14:32, Slawa Olhovchenkov wrote:
> On Mon, Oct 28, 2013 at 02:22:16PM -0700, Jordan Hubbard wrote:
>
>>
>> On Oct 28, 2013, at 2:28 AM, Slawa Olhovchenkov
>> wrote:
>>
>>> As I see ZFS cretate seperate thread for earch txg writing.
>>> Also for writing to L2ARC. As result -- up to several thousands
>>> threads created and destoyed per second. And hundreds thousands
>>> page allocations, zeroing, maping unmaping and freeing per
>>> seconds. Very high overhead.
>>
>> How are you measuring the number of threads being created /
>> destroyed? This claim seems erroneous given how the ZFS thread
>> pool mechanism actually works (and yes, there are thread pools
>> already).
>>
>> It would be helpful to both see your measurement methodology and
>> the workload you are using in your tests.
>
> Semi-indirect. dtrace -n 'fbt:kernel:vm_object_terminate:entry {
> @traces[stack()] = count(); }'
>
> After some (2-3) seconds
>
> kernel`vnode_destroy_vobject+0xb9 zfs.ko`zfs_freebsd_reclaim+0x2e
> kernel`VOP_RECLAIM_APV+0x78 kernel`vgonel+0x134
> kernel`vnlru_free+0x362 kernel`vnlru_proc+0x61e
> kernel`fork_exit+0x11f kernel`0x80cdbfde 2490
>
> I don't have user process created threads nor do fork/exit.
This has nothing to do with fork/exit but does suggest that you are
running of vnodes. What does sysctl -a | grep vnode say?
Cheers,
- --
Xin LI https://www.delphij.net/
FreeBSD - The Power to Serve! Live free or die
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Re: ZFS txg implementation flaw
On Mon, Oct 28, 2013 at 02:22:16PM -0700, Jordan Hubbard wrote:
>
> On Oct 28, 2013, at 2:28 AM, Slawa Olhovchenkov wrote:
>
> > As I see ZFS cretate seperate thread for earch txg writing.
> > Also for writing to L2ARC.
> > As result -- up to several thousands threads created and destoyed per
> > second. And hundreds thousands page allocations, zeroing, maping
> > unmaping and freeing per seconds. Very high overhead.
>
> How are you measuring the number of threads being created / destroyed? This
> claim seems erroneous given how the ZFS thread pool mechanism actually works
> (and yes, there are thread pools already).
>
> It would be helpful to both see your measurement methodology and the workload
> you are using in your tests.
Semi-indirect.
dtrace -n 'fbt:kernel:vm_object_terminate:entry { @traces[stack()] = count(); }'
After some (2-3) seconds
kernel`vnode_destroy_vobject+0xb9
zfs.ko`zfs_freebsd_reclaim+0x2e
kernel`VOP_RECLAIM_APV+0x78
kernel`vgonel+0x134
kernel`vnlru_free+0x362
kernel`vnlru_proc+0x61e
kernel`fork_exit+0x11f
kernel`0x80cdbfde
2490
I don't have user process created threads nor do fork/exit.
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Re: ZFS txg implementation flaw
On Mon, Oct 28, 2013 at 04:51:02PM -0400, Allan Jude wrote: > On 2013-10-28 16:48, Slawa Olhovchenkov wrote: > > On Mon, Oct 28, 2013 at 02:28:04PM -0400, Allan Jude wrote: > > > >> On 2013-10-28 14:16, Slawa Olhovchenkov wrote: > >>> On Mon, Oct 28, 2013 at 10:45:02AM -0700, aurfalien wrote: > >>> > On Oct 28, 2013, at 2:28 AM, Slawa Olhovchenkov wrote: > > > I can be wrong. > > As I see ZFS cretate seperate thread for earch txg writing. > > Also for writing to L2ARC. > > As result -- up to several thousands threads created and destoyed per > > second. And hundreds thousands page allocations, zeroing, maping > > unmaping and freeing per seconds. Very high overhead. > > > > In systat -vmstat I see totfr up to 60, prcfr up to 20. > > > > Estimated overhead -- 30% of system time. > > > > Can anybody implement thread and page pool for txg? > Would lowering vfs.zfs.txg.timeout be a way to tame or mitigate this? > >>> vfs.zfs.txg.timeout: 5 > >>> > >>> Only x5 lowering (less in real case with burst writing). And more > >>> fragmentation on writing and etc. > >>> ___ > >>> freebsd-current@freebsd.org mailing list > >>> http://lists.freebsd.org/mailman/listinfo/freebsd-current > >>> To unsubscribe, send any mail to "freebsd-current-unsubscr...@freebsd.org" > >> >From my understanding, increasing the timeout so you are doing fewer > >> transaction groups, would actually be the way to increase performance, > >> at the cost of 'bursty' writing and the associated uneven latency. > > This (increasing the timeout) is dramaticaly decreasing read > > performance by very high IO burst. > It shouldn't affect read performance, except during the flush operations > (every txg.timeout seconds) Yes, I talk about this time. > If you watch with 'gstat' or 'gstat -f ada.$' you should see the cycle > > reading quickly, then every txg.timeout seconds (and for maybe longer), > it flushes the entire transaction group (may be 100s of MBs) to the > disk, this high write load may make reads slow until it is finished. Yes. And read may delayed for some seconds. This is unacceptable for may case. ___ freebsd-current@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-current To unsubscribe, send any mail to "freebsd-current-unsubscr...@freebsd.org"
Re: ZFS txg implementation flaw
On 2013-10-28 16:48, Slawa Olhovchenkov wrote: > On Mon, Oct 28, 2013 at 02:28:04PM -0400, Allan Jude wrote: > >> On 2013-10-28 14:16, Slawa Olhovchenkov wrote: >>> On Mon, Oct 28, 2013 at 10:45:02AM -0700, aurfalien wrote: >>> On Oct 28, 2013, at 2:28 AM, Slawa Olhovchenkov wrote: > I can be wrong. > As I see ZFS cretate seperate thread for earch txg writing. > Also for writing to L2ARC. > As result -- up to several thousands threads created and destoyed per > second. And hundreds thousands page allocations, zeroing, maping > unmaping and freeing per seconds. Very high overhead. > > In systat -vmstat I see totfr up to 60, prcfr up to 20. > > Estimated overhead -- 30% of system time. > > Can anybody implement thread and page pool for txg? Would lowering vfs.zfs.txg.timeout be a way to tame or mitigate this? >>> vfs.zfs.txg.timeout: 5 >>> >>> Only x5 lowering (less in real case with burst writing). And more >>> fragmentation on writing and etc. >>> ___ >>> freebsd-current@freebsd.org mailing list >>> http://lists.freebsd.org/mailman/listinfo/freebsd-current >>> To unsubscribe, send any mail to "freebsd-current-unsubscr...@freebsd.org" >> >From my understanding, increasing the timeout so you are doing fewer >> transaction groups, would actually be the way to increase performance, >> at the cost of 'bursty' writing and the associated uneven latency. > This (increasing the timeout) is dramaticaly decreasing read > performance by very high IO burst. It shouldn't affect read performance, except during the flush operations (every txg.timeout seconds) If you watch with 'gstat' or 'gstat -f ada.$' you should see the cycle reading quickly, then every txg.timeout seconds (and for maybe longer), it flushes the entire transaction group (may be 100s of MBs) to the disk, this high write load may make reads slow until it is finished. Over the course of a full 60 seconds, this should result in a higher total read performance, although it will be uneven, slower during the write cycle. -- Allan Jude ___ freebsd-current@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-current To unsubscribe, send any mail to "freebsd-current-unsubscr...@freebsd.org"
Re: ZFS txg implementation flaw
On Mon, Oct 28, 2013 at 02:28:04PM -0400, Allan Jude wrote: > On 2013-10-28 14:16, Slawa Olhovchenkov wrote: > > On Mon, Oct 28, 2013 at 10:45:02AM -0700, aurfalien wrote: > > > >> On Oct 28, 2013, at 2:28 AM, Slawa Olhovchenkov wrote: > >> > >>> I can be wrong. > >>> As I see ZFS cretate seperate thread for earch txg writing. > >>> Also for writing to L2ARC. > >>> As result -- up to several thousands threads created and destoyed per > >>> second. And hundreds thousands page allocations, zeroing, maping > >>> unmaping and freeing per seconds. Very high overhead. > >>> > >>> In systat -vmstat I see totfr up to 60, prcfr up to 20. > >>> > >>> Estimated overhead -- 30% of system time. > >>> > >>> Can anybody implement thread and page pool for txg? > >> Would lowering vfs.zfs.txg.timeout be a way to tame or mitigate this? > > vfs.zfs.txg.timeout: 5 > > > > Only x5 lowering (less in real case with burst writing). And more > > fragmentation on writing and etc. > > ___ > > freebsd-current@freebsd.org mailing list > > http://lists.freebsd.org/mailman/listinfo/freebsd-current > > To unsubscribe, send any mail to "freebsd-current-unsubscr...@freebsd.org" > >From my understanding, increasing the timeout so you are doing fewer > transaction groups, would actually be the way to increase performance, > at the cost of 'bursty' writing and the associated uneven latency. This (increasing the timeout) is dramaticaly decreasing read performance by very high IO burst. ___ freebsd-current@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-current To unsubscribe, send any mail to "freebsd-current-unsubscr...@freebsd.org"
Re: ZFS txg implementation flaw
On 2013-10-28 14:25, aurfalien wrote: > On Oct 28, 2013, at 11:16 AM, Slawa Olhovchenkov wrote: > >> On Mon, Oct 28, 2013 at 10:45:02AM -0700, aurfalien wrote: >> >>> On Oct 28, 2013, at 2:28 AM, Slawa Olhovchenkov wrote: >>> I can be wrong. As I see ZFS cretate seperate thread for earch txg writing. Also for writing to L2ARC. As result -- up to several thousands threads created and destoyed per second. And hundreds thousands page allocations, zeroing, maping unmaping and freeing per seconds. Very high overhead. In systat -vmstat I see totfr up to 60, prcfr up to 20. Estimated overhead -- 30% of system time. Can anybody implement thread and page pool for txg? >>> Would lowering vfs.zfs.txg.timeout be a way to tame or mitigate this? >> vfs.zfs.txg.timeout: 5 >> >> Only x5 lowering (less in real case with burst writing). And more >> fragmentation on writing and etc. > So leave it default in other words. > > Good to know. > > - aurf > > ___ > freebsd-current@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-current > To unsubscribe, send any mail to "freebsd-current-unsubscr...@freebsd.org" The default is the default for a reason, although the original default was 30 -- Allan Jude ___ freebsd-current@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-current To unsubscribe, send any mail to "freebsd-current-unsubscr...@freebsd.org"
Re: ZFS txg implementation flaw
On Oct 28, 2013, at 11:16 AM, Slawa Olhovchenkov wrote: > On Mon, Oct 28, 2013 at 10:45:02AM -0700, aurfalien wrote: > >> >> On Oct 28, 2013, at 2:28 AM, Slawa Olhovchenkov wrote: >> >>> I can be wrong. >>> As I see ZFS cretate seperate thread for earch txg writing. >>> Also for writing to L2ARC. >>> As result -- up to several thousands threads created and destoyed per >>> second. And hundreds thousands page allocations, zeroing, maping >>> unmaping and freeing per seconds. Very high overhead. >>> >>> In systat -vmstat I see totfr up to 60, prcfr up to 20. >>> >>> Estimated overhead -- 30% of system time. >>> >>> Can anybody implement thread and page pool for txg? >> >> Would lowering vfs.zfs.txg.timeout be a way to tame or mitigate this? > > vfs.zfs.txg.timeout: 5 > > Only x5 lowering (less in real case with burst writing). And more > fragmentation on writing and etc. So leave it default in other words. Good to know. - aurf ___ freebsd-current@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-current To unsubscribe, send any mail to "freebsd-current-unsubscr...@freebsd.org"
Re: ZFS txg implementation flaw
On 2013-10-28 14:16, Slawa Olhovchenkov wrote: > On Mon, Oct 28, 2013 at 10:45:02AM -0700, aurfalien wrote: > >> On Oct 28, 2013, at 2:28 AM, Slawa Olhovchenkov wrote: >> >>> I can be wrong. >>> As I see ZFS cretate seperate thread for earch txg writing. >>> Also for writing to L2ARC. >>> As result -- up to several thousands threads created and destoyed per >>> second. And hundreds thousands page allocations, zeroing, maping >>> unmaping and freeing per seconds. Very high overhead. >>> >>> In systat -vmstat I see totfr up to 60, prcfr up to 20. >>> >>> Estimated overhead -- 30% of system time. >>> >>> Can anybody implement thread and page pool for txg? >> Would lowering vfs.zfs.txg.timeout be a way to tame or mitigate this? > vfs.zfs.txg.timeout: 5 > > Only x5 lowering (less in real case with burst writing). And more > fragmentation on writing and etc. > ___ > freebsd-current@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-current > To unsubscribe, send any mail to "freebsd-current-unsubscr...@freebsd.org" >From my understanding, increasing the timeout so you are doing fewer transaction groups, would actually be the way to increase performance, at the cost of 'bursty' writing and the associated uneven latency. -- Allan Jude ___ freebsd-current@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-current To unsubscribe, send any mail to "freebsd-current-unsubscr...@freebsd.org"
Re: ZFS txg implementation flaw
On Oct 28, 2013, at 2:28 AM, Slawa Olhovchenkov wrote: > I can be wrong. > As I see ZFS cretate seperate thread for earch txg writing. > Also for writing to L2ARC. > As result -- up to several thousands threads created and destoyed per > second. And hundreds thousands page allocations, zeroing, maping > unmaping and freeing per seconds. Very high overhead. > > In systat -vmstat I see totfr up to 60, prcfr up to 20. > > Estimated overhead -- 30% of system time. > > Can anybody implement thread and page pool for txg? Would lowering vfs.zfs.txg.timeout be a way to tame or mitigate this? - aurf ___ freebsd-current@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-current To unsubscribe, send any mail to "freebsd-current-unsubscr...@freebsd.org"
Re: ZFS txg implementation flaw
On Mon, Oct 28, 2013 at 10:45:02AM -0700, aurfalien wrote: > > On Oct 28, 2013, at 2:28 AM, Slawa Olhovchenkov wrote: > > > I can be wrong. > > As I see ZFS cretate seperate thread for earch txg writing. > > Also for writing to L2ARC. > > As result -- up to several thousands threads created and destoyed per > > second. And hundreds thousands page allocations, zeroing, maping > > unmaping and freeing per seconds. Very high overhead. > > > > In systat -vmstat I see totfr up to 60, prcfr up to 20. > > > > Estimated overhead -- 30% of system time. > > > > Can anybody implement thread and page pool for txg? > > Would lowering vfs.zfs.txg.timeout be a way to tame or mitigate this? vfs.zfs.txg.timeout: 5 Only x5 lowering (less in real case with burst writing). And more fragmentation on writing and etc. ___ freebsd-current@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-current To unsubscribe, send any mail to "freebsd-current-unsubscr...@freebsd.org"
ZFS txg implementation flaw
I can be wrong. As I see ZFS cretate seperate thread for earch txg writing. Also for writing to L2ARC. As result -- up to several thousands threads created and destoyed per second. And hundreds thousands page allocations, zeroing, maping unmaping and freeing per seconds. Very high overhead. In systat -vmstat I see totfr up to 60, prcfr up to 20. Estimated overhead -- 30% of system time. Can anybody implement thread and page pool for txg? ___ freebsd-current@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-current To unsubscribe, send any mail to "freebsd-current-unsubscr...@freebsd.org"
