From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Paul Mackerras <paulus@samba.org>
Cc: linuxppc-dev@ozlabs.org
Subject: Re: [PATCH] powerpc: Only demote individual slices rather than whole process
Date: Sun, 22 Jun 2008 10:29:09 +1000 [thread overview]
Message-ID: <1214094549.8011.196.camel@pasglop> (raw)
In-Reply-To: <18520.40232.383998.820059@cargo.ozlabs.ibm.com>
On Wed, 2008-06-18 at 15:29 +1000, Paul Mackerras wrote:
> At present, if we have a kernel with a 64kB page size, and some
> process maps something that has to be mapped with 4kB pages (such as a
> cache-inhibited mapping on POWER5+, or the eHCA infiniband queue-pair
> pages), we change the process to use 4kB pages everywhere. This hurts
> the performance of HPC programs that access eHCA from userspace.
>
> With this patch, the kernel will only demote the slice(s) containing
> the eHCA or cache-inhibited mappings, leaving the remaining slices
> able to use 64kB hardware pages.
>
> This also changes the slice_get_unmapped_area code so that it is
> willing to place a 64k-page mapping into (or across) a 4k-page slice
> if there is no better alternative, i.e. if the program specified
> MAP_FIXED or if there is not sufficient space available in slices that
> are either empty or already have 64k-page mappings in them.
>
> Signed-off-by: Paul Mackerras <paulus@samba.org>
> ---
Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
(pending some torture testing of course :-)
Ben.
prev parent reply other threads:[~2008-06-22 0:29 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-06-18 5:29 [PATCH] powerpc: Only demote individual slices rather than whole process Paul Mackerras
2008-06-22 0:29 ` Benjamin Herrenschmidt [this message]
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