Date: Fri, 14 Oct 2011 13:17:01 -0400 From: "b. f." <bf1783@googlemail.com> To: freebsd-fs@FreeBSD.org, Miroslav Lachman <000.fbsd@quip.cz> Subject: Re: dirhash and dynamic memory allocation Message-ID: <CAGFTUwPH73wrtp98edRnot7_00Hp71U3HxVE69Hu7LUp0NxH0g@mail.gmail.com>
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Miroslav Lachman wrote: > Jeremy Chadwick wrote: > > On Fri, Oct 14, 2011 at 02:33:18PM +0200, Miroslav Lachman wrote: > >> Ivan Voras wrote: > >>> On 14/10/2011 11:20, Miroslav Lachman wrote: ... > >>>> I tried some tuning of dirhash on our servers and after googlig a bit, I > >>>> found an old GSoC project wiki page about Dynamic Memory Allocation for > >>>> Dirhash: http://wiki.freebsd.org/DirhashDynamicMemory > >>>> Is there any reason not to use it / not commit it to HEAD? ... > >> Is this change documented somewhere? Maybe it could be noticed on > >> DirhashDynamicMemory wiki page. Otherwise it seems as abandoned GSoC > >> project. > > > > There is no real form of "documentation" for this kind of change, but I > > do remember it being discussed on the mailing list at some point (an > > announcement or something? I forget -- man it was a while ago). > > I didn't mean real doc (man page or handbook), but just some official > place (release notes?) stating the change of the dirhash behavior. >From the page you cited: "Get code in a state suitable for being committed to -CURRENT. Done ... (2009-7-7) I committed the dirhash vm_lowmem handler to -CURRENT about a month ago, and it will be included in 8.0-RELEASE. Also I plan to commit a backport of these changes to 7-STABLE, probably around September." >From http://www.FreeBSD.org/releases/7.3R/relnotes-detailed.html : "UFS_DIRHASH (enabled by default) now supports removing the cache data when the system memory is low (via vm_lowmem event handler). A bug that the system caused a panic when decreasing a sysctl variable vfs.ufs.dirhash_maxmem below the current amount of memory used by UFS_DIRHASH, has been fixed." In the commit logs: http://svnweb.FreeBSD.org/base/head/sys/ufs/ufs/ufs_dirhash.c?view=log So the changes have been documented. Perhaps not in exhaustive detail, but enough to provide a basis for further inquiry. And as someone pointed out, there are the suggestively-named OIDs, and their descriptions. b.
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