Date: Mon, 28 Oct 2013 14:38:30 -0700 From: Xin Li <delphij@delphij.net> To: Slawa Olhovchenkov <slw@zxy.spb.ru>, Jordan Hubbard <jkh@ixsystems.com> Cc: freebsd-fs@freebsd.org, freebsd-current@freebsd.org Subject: Re: ZFS txg implementation flaw Message-ID: <526ED956.10202@delphij.net> In-Reply-To: <20131028213204.GX63359@zxy.spb.ru> References: <20131028092844.GA24997@zxy.spb.ru> <9A00B135-7D28-47EB-ADB3-E87C38BAC6B6@ixsystems.com> <20131028213204.GX63359@zxy.spb.ru>
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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 <slw@zxy.spb.ru>
>> 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`0xffffffff80cdbfde 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 <delphij@delphij.net> https://www.delphij.net/
FreeBSD - The Power to Serve! Live free or die
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