From: Matt Mackall <mpm@selenic.com>
To: Richard Guenther <rguenther@suse.de>
Cc: Balbir Singh <balbir@linux.vnet.ibm.com>,
Nikanth Karthikesan <knikanth@suse.de>,
KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
linux-mm@kvack.org, Andrew Morton <akpm@linux-foundation.org>,
Michael Matz <matz@novell.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2] After swapout/swapin private dirty mappings are reported clean in smaps
Date: Wed, 15 Sep 2010 09:46:22 -0500 [thread overview]
Message-ID: <1284561982.21906.280.camel@calx> (raw)
In-Reply-To: <alpine.LNX.2.00.1009151612450.28912@zhemvz.fhfr.qr>
On Wed, 2010-09-15 at 16:14 +0200, Richard Guenther wrote:
> On Wed, 15 Sep 2010, Balbir Singh wrote:
>
> > * Nikanth Karthikesan <knikanth@suse.de> [2010-09-15 12:01:11]:
> >
> > > How? Current smaps information without this patch provides incorrect
> > > information. Just because a private dirty page became part of swap cache, it
> > > shown as clean and backed by a file. If it is shown as clean and backed by
> > > swap then it is fine.
> > >
> >
> > How is GDB using this information?
>
> GDB counts the number of dirty and swapped pages in a private mapping and
> based on that decides whether it needs to dump it to a core file or not.
> If there are no dirty or swapped pages gdb assumes it can reconstruct
> the mapping from the original backing file. This way for example
> shared libraries do not end up in the core file.
This whole discussion is a little disturbing.
The page is being reported clean as per the kernel's definition of
clean, full stop.
So either there's a latent bug/inconsistency in the kernel VM or
external tools are misinterpreting this data. But smaps is just
reporting what's there, the fault doesn't lie in smaps. So fixing smaps
just hides the problem, wherever it is.
Richard's report that the page is still clean after swapoff suggests the
inconsistency lies in the VM.
--
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next prev parent reply other threads:[~2010-09-15 14:47 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-09-14 11:10 [PATCH] After swapout/swapin private dirty mappings become clean Nikanth Karthikesan
2010-09-14 11:33 ` Richard Guenther
2010-09-14 17:12 ` Nikanth Karthikesan
2010-09-14 17:14 ` [PATCH v2] After swapout/swapin private dirty mappings are reported clean in smaps Nikanth Karthikesan
2010-09-15 0:26 ` KOSAKI Motohiro
2010-09-15 4:38 ` Nikanth Karthikesan
2010-09-15 4:48 ` KOSAKI Motohiro
2010-09-15 5:04 ` Nikanth Karthikesan
2010-09-15 5:20 ` KOSAKI Motohiro
2010-09-15 6:31 ` Nikanth Karthikesan
2010-09-15 14:09 ` Balbir Singh
2010-09-15 14:14 ` Richard Guenther
2010-09-15 14:46 ` Matt Mackall [this message]
2010-09-15 14:53 ` Richard Guenther
2010-09-15 17:24 ` Matt Mackall
2010-09-15 19:08 ` Richard Guenther
2010-09-15 19:18 ` Hugh Dickins
2010-09-15 19:46 ` Matt Mackall
2010-09-15 19:53 ` Richard Guenther
2010-09-15 21:47 ` Hugh Dickins
2010-09-16 3:26 ` [PATCH] Export amount of anonymous memory in a mapping via smaps Nikanth Karthikesan
2010-09-16 3:52 ` KOSAKI Motohiro
2010-09-16 6:04 ` [PATCH] Document the new Anonymous field in smaps Nikanth Karthikesan
2010-09-16 6:34 ` [PATCH] smaps: fix dirty pages accounting KOSAKI Motohiro
2010-09-16 16:56 ` Hugh Dickins
2010-09-16 16:50 ` [PATCH] Document the new Anonymous field in smaps Hugh Dickins
2010-09-17 6:04 ` [PATCH v2] " Nikanth Karthikesan
2010-09-20 7:11 ` Hugh Dickins
2010-09-20 19:24 ` Matt Mackall
2010-09-16 16:40 ` [PATCH] Export amount of anonymous memory in a mapping via smaps Hugh Dickins
2010-09-15 17:41 ` [PATCH v2] After swapout/swapin private dirty mappings are reported clean in smaps Balbir Singh
2010-09-19 17:37 ` Nikanth Karthikesan
2010-09-19 17:38 ` [PATCH] Document /proc/pid/pagemap in Documentation/filesystems/proc.txt Nikanth Karthikesan
2010-09-20 21:27 ` Matt Mackall
2010-09-20 5:24 ` [PATCH v2] After swapout/swapin private dirty mappings are reported clean in smaps Nikanth Karthikesan
2010-09-20 14:30 ` Richard Guenther
2010-09-15 0:24 ` [PATCH] After swapout/swapin private dirty mappings become clean KOSAKI Motohiro
2010-09-15 4:37 ` Nikanth Karthikesan
2010-09-15 4:46 ` KOSAKI Motohiro
2010-09-15 5:00 ` Nikanth Karthikesan
2010-09-15 5:15 ` KOSAKI Motohiro
2010-09-15 6:29 ` Nikanth Karthikesan
2010-09-15 8:40 ` Richard Guenther
2010-09-16 1:29 ` KOSAKI Motohiro
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