lkml.org 
[lkml]   [2002]   [Feb]   [23]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH] only irq-safe atomic ops
From
Date
Andrew Morton <akpm@zip.com.au> writes:
> > >
> > I can tell you that Irix has just such a global counter for the amount of
> > delayed allocate pages - and it gets to be a major point of cache contention
> > once you get to larger cpu counts. So avoiding that from the start would
> > be good.
>
> Ah, good info. Thanks. I'll fix it with a big "FIXME" comment for now,
> fix it for real when Rusty's per-CPU infrastructure appears.

Just curious -- how do you want to fix it for real?
As far as I can see a delalloc counter needs to be exact to avoid OOM
deadlocks, but making it per CPU would require doing the accounting inexact.

The only way I can imagine is to use the 'cookie jar' trick by grabbing
some amount per CPU and only going back to the global counter when the
local jar is used up, but that seems to have some drawbacks too, like
keeping a lot of pages free with higher CPU counts.

-Andi


-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2005-03-22 13:24    [W:0.022 / U:0.428 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site