Date: Wed, 9 Oct 2013 13:59:28 +0100 From: RW <rwmaillists@googlemail.com> To: freebsd-hackers@freebsd.org Subject: Re: Call fo comments - raising vfs.ufs.dirhash_reclaimage? Message-ID: <20131009135928.702f1910@gumby.homeunix.com> In-Reply-To: <CACYV=-EU86U6-q%2B-K1kVBPPTy_3vZJgjOf83hD9roqBYwY0YEw@mail.gmail.com> References: <kvkvi7$iv7$1@ger.gmane.org> <20130828181228.0d3618dd@ernst.home> <CAF-QHFU80YC3W-k%2BTKM=y3JiVYi=1fp5CJjbCCk1y0VKXzcRQg@mail.gmail.com> <201309031507.33098.jhb@freebsd.org> <CACYV=-GZPbC03stS6PsihfJ688kbjna2-n0%2BPdctr3L9hvSvag@mail.gmail.com> <20131008063433.GA47506@x2.osted.lan> <CAJ-VmonngDnZuphdsSP%2B4qGaz4u%2B%2B-bxzqrP5pqi80OOj64GSQ@mail.gmail.com> <CACYV=-HYCNeuP70JdFBrG9vXXj-E6E%2BOHcJ7Ov-Dzazx_59cag@mail.gmail.com> <20131008233806.54bb0483@gumby.homeunix.com> <CACYV=-EU86U6-q%2B-K1kVBPPTy_3vZJgjOf83hD9roqBYwY0YEw@mail.gmail.com>
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On Tue, 8 Oct 2013 16:01:25 -0700 Davide Italiano wrote: > This could be probably changed -- from what | see even under high > memory pressure this wasn't a problem but all in all I agree with you > that we shouldn't loop forever but limit the number of pass on the > list to a somewhat constant number, to prevent pathological cases. I don't see any need to loop. > > I don't believe that's true. Under most circustances the existing > > scheme free more memory. The only case when yours frees more is > > when 90% of the entries are locked. > > Well, no. Here you can set the threshold to a more aggressive value so > that you reclaim more memory every time. Note that this was not > possible in the previous version, so, if you could have a situation > where all your cache entries were not touched for 15 or even 30 > seconds they would have kept around, and you can destroy up to 10% of > them everytime lowmem event is called. Outside of contrived stress tests I think it's very rare for a significant fraction of the cache to have been accessed in the last minute - particularly on large caches where this matters most.
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