Date: Tue, 29 Oct 2013 01:32:04 +0400 From: Slawa Olhovchenkov <slw@zxy.spb.ru> To: Jordan Hubbard <jkh@ixsystems.com> Cc: freebsd-fs@freebsd.org, freebsd-current@freebsd.org Subject: Re: ZFS txg implementation flaw Message-ID: <20131028213204.GX63359@zxy.spb.ru> In-Reply-To: <9A00B135-7D28-47EB-ADB3-E87C38BAC6B6@ixsystems.com> References: <20131028092844.GA24997@zxy.spb.ru> <9A00B135-7D28-47EB-ADB3-E87C38BAC6B6@ixsystems.com>
next in thread | previous in thread | raw e-mail | index | archive | help
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.
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?20131028213204.GX63359>