Date: Wed, 17 Aug 2016 09:18:20 +0200 From: Matthias Gamsjager <mgamsjager@gmail.com> Cc: freebsd-fs@freebsd.org Subject: Re: ZFS ARC under memory pressure Message-ID: <CA%2BD9Qhv0MW6mkEWDhGuB-S7W_6oxV5bKJ6GGpSzdqQYnNPeyhA@mail.gmail.com> In-Reply-To: <20160816193416.GM8192@zxy.spb.ru> References: <20160816193416.GM8192@zxy.spb.ru>
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On 16 August 2016 at 21:34, Slawa Olhovchenkov <slw@zxy.spb.ru> wrote: > I see issuses with ZFS ARC inder memory pressure. > ZFS ARC size can be dramaticaly reduced, up to arc_min. > > As I see memory pressure event cause call arc_lowmem and set needfree: > > arc.c:arc_lowmem > > needfree = btoc(arc_c >> arc_shrink_shift); > > After this, arc_available_memory return negative vaules (PAGESIZE * > (-needfree)) until needfree is zero. Independent how too much memory > freed. needfree set to 0 in arc_reclaim_thread(), when arc_size <= > arc_c. Until arc_size don't drop below arc_c (arc_c deceased at every > loop interation). > > arc_c droped to minimum value if arc_size fast enough droped. > > No control current to initial memory allocation. > > As result, I can see needless arc reclaim, from 10x to 100x times. > > Can some one check me and comment this? > _______________________________________________ > What version are you on?
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