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From: Iasen Kostov <tbyte@otel.net>
To: Cedric Tabary <ced@grumly.eu.org>
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Date: Wed, 14 Dec 2005 19:40:39 +0200
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Cc: freebsd-hackers@freebsd.org
Subject: Re: mmap() sendfile()
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On Mon, 2005-12-12 at 18:20 +0100, Cedric Tabary wrote:
> On 12/12/2005 08:38, Mike Silbersack wrote:
> > On Mon, 12 Dec 2005, Cedric Tabary wrote:
> >=20
> > >If it is true, doing a sendfile() on some very big files (even if not
> > >keeping the descriptor open after) will kill the cache ?
> > >
> > >Please help me to understand why this patch ? and the difference betwe=
en
> > >sendfile() and mmap() at the memory or cache level..
> > >
> > >C=C3=A9dric
> >=20
> > My memory escapes me on all the details, but there were two potential=20
> > reasons not to use sendfile with 4.x that no longer apply in 5.x and=20
> > above:
> >=20
> > 1.  Sendfile used to send small files inefficiently, sending the http=20
> > headers in one packet and the data in another.  I fixed this in 5.x.
> >=20
> > 2.  Alan Cox improved the memory efficiency of sendfile greatly, it now=
=20
> > uses a single kernel buffer for all copies of the same block of the sam=
e=20
> > file, whereas the old implementation made an in-kernel copy of each blo=
ck,=20
> > making it no more memory efficient than using mbufs.
>=20
> What about using sendfile() or mmap() on NFS ?
>=20
> C=C3=A9dric
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