From: Christoph Lameter <cl@linux.com>
To: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Nitin Gupta <ngupta@vflare.org>,
Pekka Enberg <penberg@cs.helsinki.fi>,
Minchan Kim <minchan.kim@gmail.com>,
Andrew Morton <akpm@linux-foundation.org>,
Greg KH <greg@kroah.com>,
Linux Driver Project <devel@driverdev.osuosl.org>,
linux-mm <linux-mm@kvack.org>,
linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 03/10] Use percpu stats
Date: Wed, 1 Sep 2010 15:05:54 -0500 (CDT) [thread overview]
Message-ID: <alpine.DEB.2.00.1009011501230.16013@router.home> (raw)
In-Reply-To: <1283290878.2198.28.camel@edumazet-laptop>
On Tue, 31 Aug 2010, Eric Dumazet wrote:
> > > Even for single counter, this_cpu_read(64bit) is not using an RMW
> > > (cmpxchg8) instruction, so you can get very strange results when low
> > > order 32bit wraps.
> >
> > How about fixing it so that everyone benefits?
> >
>
> IMHO, this_cpu_read() is fine as is : a _read_ operation.
>
> Dont pretend it can be used in every context, its not true.
The problem only exists on 32 bit platforms using 64 bit counters. If you
would provide this functionality for the fallback case of 64 bit counters
(here x86) in 32 bit arch code then you could use the this_cpu_*
operations in all context without your special code being replicated in
ohter places.
The additional advantage would be that for the 64bit case you would have
much faster and more compact code.
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next prev parent reply other threads:[~2010-09-01 20:06 UTC|newest]
Thread overview: 67+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-08-09 17:26 [PATCH 00/10] zram: various improvements and cleanups Nitin Gupta
2010-08-09 17:26 ` [PATCH 01/10] Replace ioctls with sysfs interface Nitin Gupta
2010-08-09 18:34 ` Pekka Enberg
2010-08-10 3:06 ` Nitin Gupta
2010-08-31 23:06 ` Dave Hansen
2010-08-09 17:26 ` [PATCH 02/10] Remove need for explicit device initialization Nitin Gupta
2010-08-09 18:36 ` Pekka Enberg
2010-08-10 3:38 ` Nitin Gupta
2010-08-09 17:26 ` [PATCH 03/10] Use percpu stats Nitin Gupta
2010-08-09 18:44 ` Pekka Enberg
2010-08-10 4:34 ` Andrew Morton
2010-08-11 16:39 ` Nitin Gupta
2010-08-11 17:18 ` Andrew Morton
2010-08-30 16:20 ` Christoph Lameter
2010-08-31 20:31 ` Nitin Gupta
2010-08-31 21:28 ` Eric Dumazet
2010-08-31 21:35 ` Christoph Lameter
2010-08-31 21:41 ` Eric Dumazet
2010-09-01 20:05 ` Christoph Lameter [this message]
2010-09-01 20:38 ` Eric Dumazet
2010-09-02 0:34 ` Christoph Lameter
2010-08-31 5:36 ` Anton Blanchard
2010-09-01 3:41 ` Anton Blanchard
2010-09-01 3:51 ` Anton Blanchard
2010-09-17 20:59 ` Andrew Morton
2010-08-09 17:26 ` [PATCH 04/10] Use percpu buffers Nitin Gupta
2010-08-09 18:57 ` Pekka Enberg
2010-08-10 4:47 ` Nitin Gupta
2010-08-10 5:05 ` Pekka Enberg
2010-08-10 5:32 ` Nitin Gupta
2010-08-10 7:36 ` Pekka Enberg
2010-08-09 17:26 ` [PATCH 05/10] Reduce per table entry overhead by 4 bytes Nitin Gupta
2010-08-09 18:59 ` Pekka Enberg
2010-08-10 4:55 ` Nitin Gupta
2010-08-09 17:26 ` [PATCH 06/10] Block discard support Nitin Gupta
2010-08-09 19:03 ` Pekka Enberg
2010-08-10 2:23 ` Jens Axboe
2010-08-10 4:54 ` Nitin Gupta
2010-08-10 15:54 ` Jens Axboe
2010-08-09 17:26 ` [PATCH 07/10] Increase compressed page size threshold Nitin Gupta
2010-08-09 18:32 ` Pekka Enberg
2010-08-09 17:26 ` [PATCH 08/10] Some cleanups Nitin Gupta
2010-08-09 19:02 ` Pekka Enberg
2010-08-09 17:26 ` [PATCH 09/10] Update zram documentation Nitin Gupta
2010-08-09 17:26 ` [PATCH 10/10] Document sysfs entries Nitin Gupta
2010-08-09 19:02 ` Pekka Enberg
2010-08-31 22:37 ` [PATCH 00/10] zram: various improvements and cleanups Greg KH
2010-09-01 3:32 ` Anton Blanchard
2010-09-09 17:24 ` OOM panics with zram Dave Hansen
2010-09-09 19:07 ` [patch -rc] oom: always return a badness score of non-zero for eligible tasks David Rientjes
2010-09-09 19:48 ` Dave Hansen
2010-09-09 21:00 ` David Rientjes
2010-09-09 21:10 ` Dave Hansen
2010-09-09 21:40 ` David Rientjes
2010-10-03 18:41 ` OOM panics with zram Nitin Gupta
2010-10-03 19:27 ` Dave Hansen
2010-10-03 19:40 ` Nitin Gupta
2010-10-04 11:08 ` Ed Tomlinson
2010-10-05 23:43 ` Greg KH
2010-10-06 2:29 ` Nitin Gupta
2010-10-06 2:36 ` Greg KH
2010-10-06 4:30 ` Nitin Gupta
2010-10-06 7:38 ` Pekka Enberg
2010-10-06 14:03 ` Greg KH
2010-10-06 14:16 ` Pekka Enberg
2010-10-06 14:53 ` Nitin Gupta
2010-10-06 14:02 ` Greg KH
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