Date: Thu, 15 Aug 2013 14:36:43 -0700 From: Colin Percival <cperciva@freebsd.org> To: Ivan Voras <ivoras@freebsd.org> Cc: svn-src-head@freebsd.org, svn-src-all@freebsd.org, src-committers@freebsd.org Subject: Re: svn commit: r254380 - in head/sys: kern sys Message-ID: <520D49EB.9060308@freebsd.org> In-Reply-To: <CAF-QHFXs11NqBMDWaHmUb%2B42z-MXh6yR3=1q92YoYNio1K3B0Q@mail.gmail.com> References: <201308152019.r7FKJI0H095440@svn.freebsd.org> <CAF-QHFXXxQC69djweY7mK1tjbTSNxTPh1=-FxUeyz1nr_0WdHQ@mail.gmail.com> <520D3AD8.4090207@freebsd.org> <CAF-QHFXs11NqBMDWaHmUb%2B42z-MXh6yR3=1q92YoYNio1K3B0Q@mail.gmail.com>
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On 08/15/13 14:34, Ivan Voras wrote: > On 15 August 2013 22:32, Colin Percival <cperciva@freebsd.org> wrote: >> No, I wasn't aware that it existed. Given that this change applies only to >> parallel operations *on the same vnode* and blogbench seems to have traffic >> randomly spread between many files, I doubt there would be any difference. > > Maybe it could help a bit on the directories? > > Whatever the problem may be (does FreeBSD still have single-writer + > multiple readers lock for processes accessing the same vnode?), there > is a huge difference in performance with blogbench between FreeBSD and > Linux. We have a single-writer / multiple-readers lock on *any particular byte* of a vnode. The rangelock code is what keeps track of this, and the locking contention I was reducing was in the rangelock bookkeeping. -- Colin Percival Security Officer Emeritus, FreeBSD | The power to serve Founder, Tarsnap | www.tarsnap.com | Online backups for the truly paranoid
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