Re: Is sendfile all that sexy?

[jamal]

On Sun, 14 Jan 2001, Ingo Molnar wrote:

>
> i believe what you are seeing here is the overhead of the pagecache. When
> using sendmsg() only, you do not read() the file every time, right? Is

In that case just a user space buffer is sent i.e no file association.

> ttcp using multiple threads?

Only a single thread, single flow setup. Very primitive but simple.

> In that case if the sendfile() is using the
> *same* file all the time, creating SMP locking overhead.
>
> if this is the case, what result do you get if you use a separate,
> isolated file per process? (And i bet that with DaveM's pagecache
> scalability patch the situation would also get much better - the global
> pagecache_lock hurts.)
>

Already doing the single file, single process. However, i do run by time
which means i could read the file from the begining(offset 0) to the end
then re-do it for as many times as 15secs would allow. Does this affect
it? I tried one 1.5 GB file, it was oopsing and given my setup right now i
cant trace it. So i am using about 170M which is read about 8 times in
the 15 secs

cheers,
jamal