Date: Thu, 29 Aug 2013 11:49:35 -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: <1377802175907-5840090.post@n5.nabble.com> In-Reply-To: <521C9E85.4060801@UToledo.edu> References: <521C9E85.4060801@UToledo.edu>
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Here is a more recent dialog between the developers. <quote Nick Barkas http://markmail.org/message/3sufphda2exjmhnq#query:+page:1+mid:3sufphda2exjmhnq+state:results On Wed, May 27, 2009 at 12:36:49PM +0200, Nick Barkas wrote: Some time during the next week or so, I plan on committing the attached patch. It adds a vm_lowmem event handler to the dirhash code in UFS2 so that dirhashes will be deleted when the system is low on memory. This allows one to increase the maximum amount of memory available for dirhash on machines that have memory to spare (via the vfs.ufs.dirhash_maxmem sysctl), and hopefully just improving behaviour in low memory situations. I worked on this last year for the summer of code with David Malone as my mentor. cool! do you have any performance numbers? graphs? :) what value do you recommend for the dirhash_maxmem sysctl? Oh yes, I have many graphs: http://wiki.freebsd.org/DirhashDynamicMemory When I ran those tests a few months ago, I used 64MB for dirhash_maxmem on a system with 1GB of memory. I have not tried other amounts of memory besides that, at least that I can recall, so please let me know what you find if you experiment with other values. Performance improvements and sometimes degradations changed depending on the type of work load, and the results on 7.x were also sometimes quite different from -current. I feel that the tests I did were pretty artificial though, so it would be great to hear about any results found with more realistic testing. Nick </quote> <quote David Malone http://markmail.org/message/3sufphda2exjmhnq#query:+page:1+mid:aerievrnrmkezehk+state:results On Wed, May 27, 2009 at 09:57:31AM -0700, Julian Elischer wrote: I was initially impressed by the numbers until I saw the scales.. a difference between 475.5 and 474 is not that significant, but if your graph scale is from 473 to 477, it looks at first glace very impressive. I think we felt the real gains here would be the ability to set the dirhash memory limits to a much larger value without having to worry about it chewing all your memory. The results basically confirm that we haven't introduced any serious regressions ;-) David. </quote> -- View this message in context: http://freebsd.1045724.n5.nabble.com/Suggest-changing-dirhash-defaults-for-FreeBSD-9-2-tp5839351p5840090.html Sent from the freebsd-stable mailing list archive at Nabble.com.
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