Date: Wed, 9 Nov 2011 16:16:33 -0800 From: Paul Saab <ps@mu.org> To: Bruce Cran <bruce@cran.org.uk> Cc: 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: <CAMYpurzXM3Yeko_LxtsdKgPsGPKW75W2cUFUq59oSb=CcAqqMA@mail.gmail.com> In-Reply-To: <4EBB104F.5010000@cran.org.uk> References: <201110281426.00013.jhb@freebsd.org> <4EB2C9DD.9090606@FreeBSD.org> <20111104160319.GD6110@elvis.mu.org> <201111080800.32717.jhb@freebsd.org> <4EBB104F.5010000@cran.org.uk>
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On Wed, Nov 9, 2011 at 3:44 PM, Bruce Cran <bruce@cran.org.uk> wrote: > On 08/11/2011 13:00, John Baldwin wrote: >> >> I think it would be fine to add flags to applications like 'tar' to allow >> users to alter their behavior in specific use cases when it makes sense. >> However, I think there are more workloads for 'tar' than the ones you are >> thinking of and we should be hesitant to change applications to use non- >> default settings. > > Someone's done that for GNU tar on Linux, adding a --no-oscache switch: > http://www.mysqlperformanceblog.com/2010/04/02/fadvise-may-be-not-what-you-expect/ So adding this support is good, but not for general purpose. It's really only good when you're pumping gigs of data through tar. I did this for libarchive (plus other work for O_DIRECT reading and creating the archive) for copying large amounts of data without impacting a running system.. It worked great for this, but then it absolutely fails when extracting a tar archive with millions of little files because of all the sync operations. Anyway, this is a good option to enable and has very practical uses out there, but it should be turned on with an option and not on by default.home | help
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