Date: Tue, 27 Aug 2013 18:15:16 -0400 From: Robert Burmeister <Robert.Burmeister@UToledo.edu> To: Sergey Kandaurov <pluknet@gmail.com> Cc: freebsd-stable <freebsd-stable@freebsd.org> Subject: Re: Suggest changing dirhash defaults for FreeBSD 9.2. Message-ID: <521D24F4.4060609@UToledo.edu> In-Reply-To: <CAE-mSOLCYRM0LRLRgmaEZN1u5ozttJZC3kWtw3Zarqik1N29zw@mail.gmail.com> References: <521C9E85.4060801@UToledo.edu> <CAE-mSOLCYRM0LRLRgmaEZN1u5ozttJZC3kWtw3Zarqik1N29zw@mail.gmail.com>
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On 8/27/2013 9:40 AM, Sergey Kandaurov wrote: > On 27 August 2013 16:41, Robert Burmeister > <Robert.Burmeister@utoledo.edu> wrote: >> I have been experimenting with dirhash settings, and have scoured the internet for other peoples' experience with it. >> (I found the performance improvement in compiling has forestalled the need to add an SSD drive. ;-) >> >> I believe that increasing the following values by 10 would benefit most FreeBSD users without disadvantage. >> >> vfs.ufs.dirhash_maxmem: 2097152 to 20971520 >> >> vfs.ufs.dirhash_reclaimage: 5 to 50 or 60 > vfs.ufs.dirhash_maxmem is further autotuned based on available physical memory. > See r214359 for details. > Sorry, the documentation has not been updated since 2008. https://wiki.freebsd.org/DirhashDynamicMemory What about bumping up vfs.ufs.dirhash_reclaimage > all hashes older than 5 seconds (tunable via a sysctl, > vfs.ufs.dirhash_reclaimage) will always be deleted when a vm_lowmem event > occurs, and if that doesn't free up at least 10% of the memory currently being > used by dirhash, more hashes will be destroyed from the head of the TAILQ > until we do free up at least 10% of the memory initially used. As the memory scavenger will keep nibbling until at least 10% of the cache is free, eradicating all entries older than 5 seconds for the first chop seems overly aggressive.
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