Date: Sun, 14 Feb 2010 20:33:37 +0000 From: Jonathan Belson <jon@witchspace.com> To: Artem Belevich <fbsdlist@src.cx> Cc: freebsd-stable@freebsd.org Subject: Re: More zfs benchmarks Message-ID: <7C406D93-F94F-4A0C-AE49-6A6D8C1C2868@witchspace.com> In-Reply-To: <50780815-0D98-4910-B81A-1F41455AC856@witchspace.com> References: <EC10D2E9-04C7-4976-B377-62E79D9BE47A@witchspace.com> <ed91d4a81002141113m323eb9eyef40f7cbd6427bc5@mail.gmail.com> <50780815-0D98-4910-B81A-1F41455AC856@witchspace.com>
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On 14 Feb 2010, at 20:26, Jonathan Belson wrote: > On 14 Feb 2010, at 19:13, Artem Belevich wrote: >> Can you check if kstat.zfs.misc.arcstats.memory_throttle_count sysctl >> increments during your tests? >>=20 >> ZFS self-throttles writes if it thinks system is running low on >> memory. Unfortunately on FreeBSD the 'free' list is a *very* >> conservative indication of available memory so ZFS often starts >> throttling before it's really needed. With only 2GB in the system, >> that's probably what slows you down. >=20 > I tested a number of times during a 2GB write to a zfs partition and = the count stayed at 0. Oh, I should add that I use the following settings from the zfs tuning = guide: vm.kmem_size=3D"1024M" vm.kmem_size_max=3D"1024M" vfs.zfs.arc_max=3D"100M" Cheers, --Jon
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