> On Mon, 16 Nov 1998, Stephen C. Tweedie wrote:
> > On Sun, 15 Nov 1998 20:38:05 +0100 (MET), Gerard Roudier
> > <groudier@club-internet.fr> said:
> >
> > > My understanding of Linux architecture is that IO blocks coalescing only
> > > occurs in ll_rw_blk.c.
> >
> > Yes, except for scsi which does its Own Thing, of course.
>
> When I imagine a system with a large memory space, for example 1 GB,
> running several hundreds of processes (thousands?) performing writes, all
> of them sharing the only 64 requests (NR_REQUEST) in 2.1.128 kernel, I
> cannot believe that coalescence will work that well.
> Did I miss something important?
I agree mostly. A very simple "fix" to this situation would be to make
the queue longer as you hint. Even make it a tunable kernel parameter
under /proc. If you have 1 GB of memory you can spare a few bytes for a
larger queue. Although against this, we can argue that such a large
system *should* already have an intelligent disk controller (RAID?) that
has sufficiently large buffers to do these optimizations. Just my 2
centavos...
Cheers,
Rafael
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