Date: Tue, 17 Aug 2010 16:24:34 -0500 From: Alan Cox <alan.l.cox@gmail.com> To: Dimitry Andric <dimitry@andric.com> Cc: current@freebsd.org Subject: Re: Official request: Please make GNU grep the default Message-ID: <AANLkTikCyVVmx3-f4g2x1a%2Bq6PYOCLA-KrF53NFTx7uQ@mail.gmail.com> In-Reply-To: <4C6AF13A.1080606@andric.com> References: <4C6505A4.9060203@FreeBSD.org> <20100813085235.GA16268@freebsd.org> <4C66C010.3040308@FreeBSD.org> <4C673F02.8000805@FreeBSD.org> <20100815013438.GA8958@troutmask.apl.washington.edu> <4C67492C.5020206@FreeBSD.org> <B7A05068-9578-4341-851B-86BD9BC7A2DA@gmail.com> <8639ufd78w.fsf@ds4.des.no> <4C6844D8.5070602@andric.com> <86sk2faqdl.fsf@ds4.des.no> <4C6AAA88.5080606@andric.com> <AANLkTik-ee6iKiOoA=KMmmToS2giUOmW5JB-d1vBx9r3@mail.gmail.com> <4C6AF13A.1080606@andric.com>
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On Tue, Aug 17, 2010 at 3:29 PM, Dimitry Andric <dimitry@andric.com> wrote: > On 2010-08-17 18:29, Alan Cox wrote: > > Try it again on a memory resident file with the MAP_PREFAULT_READ option > > that is provided by this patch: > > > > http://www.cs.rice.edu/~alc/MAP_PREFAULT_READ.patch<http://www.cs.rice.edu/%7Ealc/MAP_PREFAULT_READ.patch>; > > A time trial gives: > > grep with normal mmap() 1396s > grep with prefault mmap() 1354s > grep with regular read() 1354s > > So normal mmap is ~3% slower, and prefault mmap does not seem to make > any measurable difference. I guess the added complexity is not really > worth it, for now. > Do you know what fraction of this time is being spent in the kernel? Does the value of "sysctl vm.pmap.pde.mappings" increase as a result of your test? If not, there is still room for improvement in the results with mmap(). Alan
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