Date: Mon, 28 Oct 2013 22:16:31 +0400 From: Slawa Olhovchenkov <slw@zxy.spb.ru> To: aurfalien <aurfalien@gmail.com> Cc: freebsd-fs@freebsd.org, freebsd-current@freebsd.org Subject: Re: ZFS txg implementation flaw Message-ID: <20131028181631.GV63359@zxy.spb.ru> In-Reply-To: <0F1D571E-2806-4392-A5EC-BE66A3C92BF7@gmail.com> References: <20131028092844.GA24997@zxy.spb.ru> <0F1D571E-2806-4392-A5EC-BE66A3C92BF7@gmail.com>
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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 600000, prcfr up to 200000. > > > > 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.
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