Date: Mon, 19 Apr 1999 15:58:27 -0500 (CDT) From: Jonathan Lemon <jlemon@americantv.com> To: Arjan.deVet@adv.iae.nl, hackers@freebsd.org Subject: Re: Directories not VMIO cached at all! Message-ID: <199904192058.PAA16517@free.pcs> In-Reply-To: <local.mail.freebsd-hackers/199904192019.WAA05340@adv.iae.nl> References: <local.mail.freebsd-hackers/199904171844.LAA75452@apollo.backplane.com> <local.mail.freebsd-hackers/199904191650.JAA24137@vashon.polstra.com>
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In article <local.mail.freebsd-hackers/199904192019.WAA05340@adv.iae.nl> you write: >In article <199904191650.JAA24137@vashon.polstra.com> John Polstra writes: > >>If I understand your description correctly, this fix could really >>benefit master CVSup servers such as freefall. Those servers >>typically have 8-12 running cvsupd processes, all doing tree walks >>over the same CVS repository and making a stat() call on every file. >> >>Do you think it would help? > >It helps to some extend I think. The Squid server I've been testing can >keep 32MB worth of directories cached after some tuning but because of >the enormous amount of reads and writes being done half of the >directories get removed from the cache after 5-10 minutes. We're >speaking about 750,000-1,000,000 files in 4096 directories in a >two-level hierarchy where 80% of the files is 9 KB or less in size. >B.t.w., the Squid people are working on a SquidFS which will not use >individual files anymore. Which is why Peregrine prefers to use raw disk partitions (along with a userland variant of LFS) to store the pages, since the filesystem currently imposes too much overhead for good performance. It's interesting, LFS seems to be a great web-cache filesystem, you don't really need to preserve every file, you just throw some away. No fsck; if the system crashes, you can just start all over again; after all, it _is_ a cache, right? (In Peregrine, this behavior is tunable; some environments don't want to lose the entire cache). -- Jonathan To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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