Date: Thu, 12 May 2011 21:31:15 +0400 From: =?koi8-r?B?98zBxMnNydIg5sXdxc7Lzw==?= <vladimir-its@yandex.ru> To: Mark Tinguely <marktinguely@gmail.com> Cc: freebsd-arm@freebsd.org Subject: Re: S3C2440A strange perfomance issue Message-ID: <881651305221476@web156.yandex.ru> In-Reply-To: <4DCBEB00.3040608@gmail.com> References: <578421305188959@web64.yandex.ru> <4DCBEB00.3040608@gmail.com>
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12.05.2011, 18:13, "Mark Tinguely" <marktinguely@gmail.com>: > On 5/12/2011 3:29 AM, ÷ÌÁÄÉÍÉÒ æÅÝÅÎËÏ wrote: > >> š%cc -O0 -o test test.c >> >> šand execute it: >> >> šCode: >> >> š%/usr/bin/time -l ./test >> šššššššš120.16 real šššššš119.44 user šššššššš0.16 sys >> ššššššš12177 šinvoluntary context switches >> >> štime of execution is over 120 sec ... but after system reboot: >> >> šCode: >> >> š%/usr/bin/time -l ./test >> šššššššššš2.85 real šššššššš2.55 user šššššššš0.25 sys >> ššššššššš292 šinvoluntary context switches >> >> šexecution time is 2.85(!) sec, but it's not all! >> >> šCode: >> >> š%cat test> š/dev/null >> >> š%/usr/bin/time -l ./test >> šššššššš120.40 real šššššš119.51 user šššššššš0.23 sys >> ššššššš12201 šinvoluntary context switches >> >> šOnce the file has been opened for reading (cat test> š/dev/null), execution time again increased to 120 sec (until the next reboot). >> >> šWhat is it?! > > Sounds like the executable cache gets disabled on the executable page > that is also writable issue that we talked about year or so ago. If you > want a quick test, in pmap_fix_cache(), and exit the routine immediately > if the mapping is executable. I did some tracing, and there are cases > where this is not the correct solution - executable mappings that are > really shared and cache should be disabled. I have a idea level patch > for this but never tested it well enough. > > I also notice a huge jump in "involuntary context switch" counts in your > runs. > > --Mark Tinguely please, i want code sample for use pmap_fix_cache() :) may be this issue is caching problem ... but why 'open for read' make this effect?
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