Re: [PATCH] Use MPOL_INTERLEAVE for tmpfs files

From: Andi Kleen
Date: Tue Nov 02 2004 - 11:13:55 EST

On Tue, Nov 02, 2004 at 07:46:59AM -0800, Martin J. Bligh wrote:
> > This patch causes memory allocation for tmpfs files to be distributed
> > evenly across NUMA machines. In most circumstances today, tmpfs files
> > will be allocated on the same node as the task writing to the file.
> > In many cases, particularly when large files are created, or a large
> > number of files are created by a single task, this leads to a severe
> > imbalance in free memory amongst nodes. This patch corrects that
> > situation.
> Yeah, but it also ruins your locality of reference (in a NUMA sense).
> Not convinced that's a good idea. You're guaranteeing universally consistent
> worse-case performance for everyone. And you're only looking at a situation
> where there's one allocator on the system, and that's imbalanced.
> You WANT your data to be local. That's the whole idea.

I think it depends on how you use tmpfs. When you use it for read/write
it's a good idea because you likely don't care about a bit of additional
latency and it's better to not fill up your local nodes with temporary

If you use it with mmap then you likely want local policy.

But that's a big ugly to distingush, that is why I suggested the sysctl.

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