sync_mm_rss() issues

sync_mm_rss() issues

[David Howells]

There are a couple of issues with sync_mm_rss(), as added by patch:

	commit 34e55232e59f7b19050267a05ff1226e5cd122a5
	Author: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
	Date:   Fri Mar 5 13:41:40 2010 -0800
	Subject: mm: avoid false sharing of mm_counter

 (1) You haven't implemented it for NOMMU mode.  What's the right way to do
     this?  Just give an empty function?

 (2) linux/mm.h should carry the empty function as an inline when
     CONFIG_SPLIT_RSS_COUNTING=n, rather than it being defined as an empty
     function in mm/memory.c.

David

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Re: sync_mm_rss() issues

[KAMEZAWA Hiroyuki]

On Mon, 08 Mar 2010 13:59:56 +0000
David Howells <dhowells@redhat.com> wrote:

> 
> There are a couple of issues with sync_mm_rss(), as added by patch:
> 
> 	commit 34e55232e59f7b19050267a05ff1226e5cd122a5
> 	Author: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> 	Date:   Fri Mar 5 13:41:40 2010 -0800
> 	Subject: mm: avoid false sharing of mm_counter
> 
>  (1) You haven't implemented it for NOMMU mode.  What's the right way to do
>      this?  Just give an empty function?
> 
Ah, sorry. I'll prepare empty function immediately. But I have no NOMMU
enviroment...


>  (2) linux/mm.h should carry the empty function as an inline when
>      CONFIG_SPLIT_RSS_COUNTING=n, rather than it being defined as an empty
>      function in mm/memory.c.
> 

ok.

please wait..

Sorry,
-Kame

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[BUGFIX][PATCH] fix sync_mm_rss in nommu (Was Re: sync_mm_rss() issues

[KAMEZAWA Hiroyuki]

David-san, could you check this ?
==
From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>

Fix breakage in NOMMU build

commit 34e55232e59f7b19050267a05ff1226e5cd122a5 added sync_mm_rss()
for syncing loosely accounted rss counters. It's for CONFIG_MMU but
sync_mm_rss is called even in NOMMU enviroment (kerne/exit.c, fs/exec.c).
Above commit doesn't handle it well.

This patch changes
  SPLIT_RSS_COUNTING depends on SPLIT_PTLOCKS && CONFIG_MMU

And for avoid unnecessary function calls, sync_mm_rss changed to be inlined
noop function in header file.

Reported-by: David Howells <dhowells@redhat.com>
Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
---
 include/linux/mm.h       |    6 ++++++
 include/linux/mm_types.h |    2 +-
 mm/memory.c              |    3 ---
 3 files changed, 7 insertions(+), 4 deletions(-)

Index: mmotm-2.6.33-Mar5/include/linux/mm.h
===================================================================
--- mmotm-2.6.33-Mar5.orig/include/linux/mm.h
+++ mmotm-2.6.33-Mar5/include/linux/mm.h
@@ -974,7 +974,13 @@ static inline void setmax_mm_hiwater_rss
 		*maxrss = hiwater_rss;
 }
 
+#if defined(SPLIT_RSS_COUNTING)
 void sync_mm_rss(struct task_struct *task, struct mm_struct *mm);
+#else
+static inline void sync_mm_rss(struct task_struct *task, struct mm_struct *mm)
+{
+}
+#endif
 
 /*
  * A callback you can register to apply pressure to ageable caches.
Index: mmotm-2.6.33-Mar5/mm/memory.c
===================================================================
--- mmotm-2.6.33-Mar5.orig/mm/memory.c
+++ mmotm-2.6.33-Mar5/mm/memory.c
@@ -190,9 +190,6 @@ static void check_sync_rss_stat(struct t
 {
 }
 
-void sync_mm_rss(struct task_struct *task, struct mm_struct *mm)
-{
-}
 #endif
 
 /*
Index: mmotm-2.6.33-Mar5/include/linux/mm_types.h
===================================================================
--- mmotm-2.6.33-Mar5.orig/include/linux/mm_types.h
+++ mmotm-2.6.33-Mar5/include/linux/mm_types.h
@@ -203,7 +203,7 @@ enum {
 	NR_MM_COUNTERS
 };
 
-#if USE_SPLIT_PTLOCKS
+#if USE_SPLIT_PTLOCKS && defined(CONFIG_MMU)
 #define SPLIT_RSS_COUNTING
 struct mm_rss_stat {
 	atomic_long_t count[NR_MM_COUNTERS];

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Re: [BUGFIX][PATCH] fix sync_mm_rss in nommu (Was Re: sync_mm_rss() issues

[Mike Frysinger]

On Mon, Mar 8, 2010 at 19:58, KAMEZAWA Hiroyuki wrote:
> David-san, could you check this ?
> ==
> From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
>
> Fix breakage in NOMMU build
>
> commit 34e55232e59f7b19050267a05ff1226e5cd122a5 added sync_mm_rss()
> for syncing loosely accounted rss counters. It's for CONFIG_MMU but
> sync_mm_rss is called even in NOMMU enviroment (kerne/exit.c, fs/exec.c).
> Above commit doesn't handle it well.
>
> This patch changes
>  SPLIT_RSS_COUNTING depends on SPLIT_PTLOCKS && CONFIG_MMU
>
> And for avoid unnecessary function calls, sync_mm_rss changed to be inlined
> noop function in header file.

fixes Blackfin systems ...

Signed-off-by: Mike Frysinger <vapier@gentoo.org>
-mike

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Re: [BUGFIX][PATCH] fix sync_mm_rss in nommu (Was Re: sync_mm_rss() issues

[Michal Simek]

Mike Frysinger wrote:
> On Mon, Mar 8, 2010 at 19:58, KAMEZAWA Hiroyuki wrote:
>> David-san, could you check this ?
>> ==
>> From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
>>
>> Fix breakage in NOMMU build
>>
>> commit 34e55232e59f7b19050267a05ff1226e5cd122a5 added sync_mm_rss()
>> for syncing loosely accounted rss counters. It's for CONFIG_MMU but
>> sync_mm_rss is called even in NOMMU enviroment (kerne/exit.c, fs/exec.c).
>> Above commit doesn't handle it well.
>>
>> This patch changes
>>  SPLIT_RSS_COUNTING depends on SPLIT_PTLOCKS && CONFIG_MMU
>>
>> And for avoid unnecessary function calls, sync_mm_rss changed to be inlined
>> noop function in header file.
> 
> fixes Blackfin systems ...
> 
> Signed-off-by: Mike Frysinger <vapier@gentoo.org>


fixes Microblaze noMMU systems too.

Signed-off-by: Michal Simek <monstr@monstr.eu>

You can check Microblaze noMMU system via my site
http://www.monstr.eu/wiki/doku.php?id=log:log

Will be good to add your patches to linux-next before Linus tree.

Michal


> -mike
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Re: [BUGFIX][PATCH] fix sync_mm_rss in nommu (Was Re: sync_mm_rss() issues

[Christoph Lameter]

On Tue, 9 Mar 2010, Michal Simek wrote:

> > Signed-off-by: Mike Frysinger <vapier@gentoo.org>
> Signed-off-by: Michal Simek <monstr@monstr.eu>

?? You handled this patch?

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Re: [BUGFIX][PATCH] fix sync_mm_rss in nommu (Was Re: sync_mm_rss() issues

[Mike Frysinger]

On Tue, Mar 9, 2010 at 10:41, Christoph Lameter wrote:
> On Tue, 9 Mar 2010, Michal Simek wrote:
>> > Signed-off-by: Mike Frysinger <vapier@gentoo.org>
>> Signed-off-by: Michal Simek <monstr@monstr.eu>
>
> ?? You handled this patch?

pick out the tags from the original patch
-mike

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