Date: Thu, 15 Aug 2013 13:32:24 -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: <520D3AD8.4090207@freebsd.org> In-Reply-To: <CAF-QHFXXxQC69djweY7mK1tjbTSNxTPh1=-FxUeyz1nr_0WdHQ@mail.gmail.com> References: <201308152019.r7FKJI0H095440@svn.freebsd.org> <CAF-QHFXXxQC69djweY7mK1tjbTSNxTPh1=-FxUeyz1nr_0WdHQ@mail.gmail.com>
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On 08/15/13 13:29, Ivan Voras wrote: > On 15 August 2013 22:19, Colin Percival <cperciva@freebsd.org> wrote: >> For workloads with R parallel reads and W parallel writes, this improves >> the time spent from O((R+W)^2) to O(W*(R+W)); i.e., heavy parallel-read >> workloads become significantly more scalable. >> >> No statistically significant change in buildworld time has been measured, >> but synthetic tests of parallel 'dd > /dev/null' and 'openssl enc >/dev/null' >> with the input file cached yield dramatic (up to 10x) improvement with high >> (up to 128 processes) levels of parallelism. > > That's interesting. Have you tried running the "blogbench" benchmark > before & after? 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. -- 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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