Re: Lockless page cache test results

Christoph Lameter
2006-04-26T20:31:36Z

Dave: Can you tell us more about the tree_lock contentions on I/O that you
have seen?

On Wed, 26 Apr 2006, Jens Axboe wrote:

> On Wed, Apr 26 2006, Andrew Morton wrote:
> > Christoph Lameter <clameter@sgi.com> wrote:
> > >
> > > On Wed, 26 Apr 2006, Andrew Morton wrote:
> > >
> > > > OK. That doesn't sound like something which a real application is likely
> > > > to do ;)
> > >
> > > A real application scenario may be an application that has lots of threads
> > > that are streaming data through multiple different disk channels (that
> > > are able to transfer data simultanouesly. e.g. connected to different
> > > nodes in a NUMA system) into the same address space.
> > >
> > > Something like the above is fairly typical for multimedia filters
> > > processing large amounts of data.
> >
> > >From the same file?
> >
> > To /dev/null?
>
> /dev/null doesn't have much to do with it, other than the fact that it
> basically stresses only the input side of things. Same file is the
> interesting bit of course, as that's the the granularity of the
> tree_lock.
>
> I haven't tested much else, I'll ask the tool to bench more files :)
>
> --
> Jens Axboe
>
>