Re: [PATCH 00/19] Adaptive read-ahead V8

[Wu Fengguang]

On Fri, Nov 25, 2005 at 04:43:17PM +0100, Diego Calleja wrote:
> Recently, a openoffice hacker wrote in his blog that the kernel was
> culprit of applications not starting as fast as in other systems.
> Most of the reasons he gave were wrong, but there was a interesting
> one: When you start your system, you've lots of free memory. Since
> you have lots of memory, he said it was reasonable to expect that
> kernel would readahead *heavily* everything it can to fill that
> memory as soon as possible (hoping that what you readahead'ed was
> part of the kde/gnome/openoffice libraries etc) and go back to the
> normal behaviour when your free memory is used by caches etc.
> "Teorically" it looks like a nice heuristic for desktops. Does
> adaptative readahead does something like this?

It's interesting ;)
In fact some distributions do have a read-ahead script to preload files on
startup. The readahead system call should be enough for this purpose:

NAME
       readahead - perform file readahead into page cache

SYNOPSIS
       #include <fcntl.h>

       ssize_t readahead(int fd, off64_t *offset, size_t count);

Thanks,
Wu
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