On Thu, 25 Jun 1998, Amsden, Zachary wrote:
> Possibly. But according to Squid's own doc, the primary problems
> in Squid performance are
>
> 1) Not enough memory
> 2) Too slow disks
>
> which as far as I can see aren't helped by sendfile. They also
> say "CPU limitations are rarely encountered except in very large
> caches". The same doc describes how to use clusters for large
> caches.
>
> But too slow disks and not enough memory are directly
> related problems. If the kernel has frequently used
> disk files in the buffer cache, it still needs to copy
> the data to the user space server, then copy it back
> out onto a socket. With sendfile(), it can directly
> send data from the buffer cache without any user space
> involvement. In addition, we no longer need user
> space buffers in the server, cutting down on useless
> "memory duplication", allowing for more buffer cache.
>
> With sendfile and a length parameter, user space need
> only get involved when it needs to inject data into or
> modify data going through an fd stream, which
> practically eliminates the need for any user space
> buffers. This will help just about any task I can
> think of.
>
> Zach Amsden
> amsden@andrew.cmu.edu
>
>
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