Date: Thu, 29 Aug 2013 04:25:21 -0700 (PDT) From: Robert_Burmeister <robert.burmeister@utoledo.edu> To: freebsd-stable@freebsd.org Subject: RE: Suggest changing dirhash defaults for FreeBSD 9.2. Message-ID: <1377775521691-5839900.post@n5.nabble.com> In-Reply-To: <F4E60E862AF142AFBA86521E79C0BCAA@white> References: <521C9E85.4060801@UToledo.edu> <CAE-mSOLCYRM0LRLRgmaEZN1u5ozttJZC3kWtw3Zarqik1N29zw@mail.gmail.com> <521D7552.5080008@UToledo.edu> <kvkh1j$7fj$1@ger.gmane.org> <F4E60E862AF142AFBA86521E79C0BCAA@white>
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I have seen significant benefits from setting the UFS dirhash cache tuneables to effective values, and I believe all FreeBSD users will see at least a small benefit as well. The ball for establishing production defaults appears to have been dropped in 2008. I am suggesting we pick it up and finish the job. (But not necessarily in time for the impending release.) > http://www.freebsd.org/projects/summerofcode-2008.html > Project: Dynamic memory allocation for dirhash in UFS2 > Student: Nick Barkas > Mentor: David Malone > Summary: > > Modified dirhash code in perforce is now able to free up memory used by > older dirhashes when the VM system invokes vm_lowmem events. This will > allow the default dirhash_maxmem value to be increased, improving > performance on large directory lookups when there is memory to spare on > they system. There are versions of the low memory event handling code for > both -CURRENT and 7-STABLE. A number of tests have been run showing the > new event handler seems to work properly. > > I intend to do further testing and benchmarking to find the best default > values to use for vfs.ufs.dirhash_reclaimage (the number of seconds a > dirhash can sit unused before the dirhash low memeory event handler will > unconditionally delete it) and the minimum percentage of memory that will > be freed upon vm_lowmem events even if there are not enough hashes older > than dirhash_reclaimage (currently this is hard coded to 10%). I would > also like to add some code to choose a reasonable new default > vfs.ufs.dirhash_maxmem value based upon the amount of memory in the > system, set automatically at boot time and tunable via sysctl. Once these > tweaks have been made I plan to ask for testing from more users to shake > out any bugs or potential workloads where the new code may hurt overall > performance. If someone has more up to date information please post. -- View this message in context: http://freebsd.1045724.n5.nabble.com/Suggest-changing-dirhash-defaults-for-FreeBSD-9-2-tp5839351p5839900.html Sent from the freebsd-stable mailing list archive at Nabble.com.
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