From: Greg Thelen <gthelen@google.com>
To: hannes@cmpxchg.org
Cc: Minchan Kim <minchan.kim@gmail.com>,
Andrew Morton <akpm@linux-foundation.org>,
Dave Young <hidave.darkstar@gmail.com>,
Andrea Righi <arighi@develer.com>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>,
Balbir Singh <balbir@linux.vnet.ibm.com>,
Wu Fengguang <fengguang.wu@intel.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
linux-mm <linux-mm@kvack.org>
Subject: Re: [PATCH] memcg: use do_div to divide s64 in 32 bit machine.
Date: Sat, 6 Nov 2010 10:19:35 -0700 [thread overview]
Message-ID: <AANLkTin9m65JVKRuStZ1-qhU5_1AY-GcbBRC0TodsfYC@mail.gmail.com> (raw)
In-Reply-To: <20101106010357.GD23393@cmpxchg.org>
On Fri, Nov 5, 2010 at 6:03 PM, <hannes@cmpxchg.org> wrote:
> On Sat, Nov 06, 2010 at 01:08:53AM +0900, Minchan Kim wrote:
>> Use do_div to divide s64 value. Otherwise, build would be failed
>> like Dave Young reported.
>
> I thought about that too, but then I asked myself why you would want
> to represent a number of pages as signed 64bit type, even on 32 bit?
I think the reason that 64 byte type is used for page count in
memcontrol.c is because the low level res_counter primitives operate
on 64 bit counters, even on 32 bit machines.
> Isn't the much better fix to get the types right instead?
>
I agree that consistent types between mem_cgroup_dirty_info() and
global_dirty_info() is important. There seems to be a lot of usage of
s64 for page counts in memcontrol.c, which I think is due to the
res_counter types. I think these s64 be switched to unsigned long
rather to be consistent with the rest of mm code. It looks like this
will be a clean patch, except for the lowest level where
res_counter_read_u64() is used, where some casting may be needed.
I'll post a patch for that change.
next prev parent reply other threads:[~2010-11-06 17:20 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-11-05 16:08 [PATCH] memcg: use do_div to divide s64 in 32 bit machine Minchan Kim
2010-11-05 16:34 ` Greg Thelen
2010-11-06 1:03 ` hannes
2010-11-06 17:19 ` Greg Thelen [this message]
2010-11-06 17:31 ` Minchan Kim
2010-11-07 22:14 ` [patch 0/4] memcg: variable type fixes Johannes Weiner
2010-11-07 22:14 ` [patch 1/4] memcg: use native word to represent dirtyable pages Johannes Weiner
2010-11-07 22:56 ` Minchan Kim
2010-11-08 22:25 ` Greg Thelen
2010-11-08 22:38 ` Johannes Weiner
2010-11-08 22:43 ` Greg Thelen
2010-11-16 3:37 ` KAMEZAWA Hiroyuki
2010-11-07 22:14 ` [patch 2/4] memcg: catch negative per-cpu sums in dirty info Johannes Weiner
2010-11-07 23:26 ` Minchan Kim
2010-11-08 22:28 ` Greg Thelen
2010-11-16 3:39 ` KAMEZAWA Hiroyuki
2010-11-07 22:14 ` [patch 3/4] memcg: break out event counters from other stats Johannes Weiner
2010-11-07 23:52 ` Minchan Kim
2010-11-08 23:20 ` Greg Thelen
2010-11-16 3:41 ` KAMEZAWA Hiroyuki
2010-11-07 22:14 ` [patch 4/4] memcg: use native word page statistics counters Johannes Weiner
2010-11-08 0:01 ` Minchan Kim
2010-11-08 9:08 ` Johannes Weiner
2010-11-08 22:51 ` Greg Thelen
2010-11-08 0:07 ` Minchan Kim
2010-11-08 9:37 ` memcg writeout throttling, was: " Johannes Weiner
2010-11-08 15:45 ` Wu Fengguang
2010-11-08 19:00 ` Greg Thelen
2010-11-08 23:27 ` Greg Thelen
2010-11-08 23:45 ` Johannes Weiner
2010-11-16 3:44 ` KAMEZAWA Hiroyuki
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