Date: Wed, 9 Nov 2011 16:57:06 -0800 From: Peter Wemm <peter@wemm.org> To: John Baldwin <jhb@freebsd.org> Cc: Bruce Cran <bruce@cran.org.uk>, Ed Schouten <ed@80386.nl>, Jilles Tjoelker <jilles@stack.nl>, Alfred Perlstein <alfred@freebsd.org>, arch@freebsd.org, freebsd-arch@freebsd.org Subject: Re: [PATCH] fadvise(2) system call Message-ID: <CAGE5yCoTvYNXNc37V0%2Bt783uh=6J-_J-dt_Km_4xbO7O2O2BUw@mail.gmail.com> In-Reply-To: <201111080800.32717.jhb@freebsd.org> References: <201110281426.00013.jhb@freebsd.org> <4EB2C9DD.9090606@FreeBSD.org> <20111104160319.GD6110@elvis.mu.org> <201111080800.32717.jhb@freebsd.org>
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On Tue, Nov 8, 2011 at 5:00 AM, John Baldwin <jhb@freebsd.org> wrote: > On Friday, November 04, 2011 12:03:20 pm Alfred Perlstein wrote: >> * John Baldwin <jhb@FreeBSD.org> [111103 19:38] wrote: >> > On 11/2/11 1:20 PM, Alfred Perlstein wrote: >> > >* John Baldwin<jhb@freebsd.org> =A0[111102 11:05] wrote: >> > >>On Tuesday, November 01, 2011 7:56:48 pm Bruce Cran wrote: >> > >>>On 01/11/2011 17:08, John Baldwin wrote: >> > >>>>I had found it via the web: http://linux.die.net/man/2/fadvise >> > >>>>However, after further searching it appears to be stale (if you fo= llow >> > >>>>it's cross-reference to madvise(2), that page only has links to >> > >>>>posix_fadvise() and not fadvise()). >> > >>> >> > >>>There's >> > >>>http://www.speedware.com/HPe3000_resources/MPE_to_HP-UX_cross- >> > >>reference/system_administration_cross-reference/cmd.html?cmdid=3DMS_= 1800 >> > >>>for HP-UX ("*fadvise()* was derived by HP from the IEEE POSIX >> > >>>1003.1-2001 Standard"), though it also has posix_fadvise. >> > >> >> > >>Hmm, that one actually has an extra argument. =A0I'll just go with >> > >>posix_fadvise() for now. =A0Interesting that HP lets you OR together >> > >>two policies (so you can say both "I will access this file sequentia= lly >> > >>and with noreuse"). >> > > >> > >Makes sense for gzip/tar. >> > >> > Ehh, quite possibly not for something that generic. =A0I think you onl= y >> > want to do this if you have very specific knowledge about your access >> > pattern, and I do not think they are generically applicable. >> >> You often spend time untarring the same tarball over and over >> in your workflow John? > > No, but many people will do a 'tar tvf' of a file after they generate it. > Would be rather silly to force that to go to disk every time, especially = given > tar's format where it does not have a header like zip so you have to read= the > whole darn thing for a 'tar tvf'. Did 'tar tvf' stop seeking and doing random seek/reads for raw tar files? I know it can't do this for a stream compressed file and there's no choice but to read it all. --=20 Peter Wemm - peter@wemm.org; peter@FreeBSD.org; peter@yahoo-inc.com; KI6FJV "All of this is for nothing if we don't go to the stars" - JMS/B5 "If Java had true garbage collection, most programs would delete themselves upon execution." -- Robert Sewell
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