Re: TCP Zero Copy for mmapped files

["A.D.F." <adefacc@tin.it>]

"J.A. Magallon" wrote:
> 
> On 2003.01.04 A.D.F. wrote:
> > FreeBSD 5.0 should already have a zero copy for mmapped files and
> > IMHO it would be worth to have it in Linux 2.6 too.
> >
> > It would also be very nice to be able to enable zero copy for mmapped files
> > by a config option.
> >
> > Many applications use mapped memory to serve lots of small and
> > medium sized files (4 - 1024 KB) or even a few big files
> > (think at web servers, i.e. Apache 2, etc.);  this is done to better
> > serve multiple / parallel downloads being done on the same files.
> >
> 
> Apache2 uses mmap() to open files ??

No, you cannot use mmap() to open files ... :-),
at most mmap() helps caching static file contents in order
to avoid too many open() / close() calls (which maybe slow).

Apache 2 seems to use sendfile (in blocking mode) by default,
it uses mmap() only if you enable it (see also mod_file_cache).

Other web servers (i.e. Zeus) use widely mmap() for specific
file sizes, when it is usually a strong win (specially under *BSD and
Solaris)
in big / busy servers with lots of RAM.

> So then there is a reason to include it in my patchset...

Certainly yes (after required bug fixes :-)

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