From: Vinayak Menon <vinmenon@codeaurora.org>
To: Laura Abbott <labbott@redhat.com>,
iamjoonsoo.kim@lge.com, mhocko@suse.com,
akpm@linux-foundation.org
Cc: shashim@codeaurora.org, linux-mm@kvack.org
Subject: Re: [RFC PATCH] mm: enable page poisoning early at boot
Date: Tue, 7 Mar 2017 19:38:22 +0530 [thread overview]
Message-ID: <4fdbbcd9-8779-9bab-2597-56f3125b4c74@codeaurora.org> (raw)
In-Reply-To: <83fef5a7-11e8-a46e-e624-82362f651fe8@redhat.com>
On 3/7/2017 4:47 AM, Laura Abbott wrote:
> On 03/06/2017 06:16 AM, Vinayak Menon wrote:
>> On SPARSEMEM systems page poisoning is enabled after buddy is up, because
>> of the dependency on page extension init. This causes the pages released
>> by free_all_bootmem not to be poisoned. This either delays or misses
>> the identification of some issues because the pages have to undergo another
>> cycle of alloc-free-alloc for any corruption to be detected.
>> Enable page poisoning early by getting rid of the PAGE_EXT_DEBUG_POISON
>> flag. Since all the free pages will now be poisoned, the flag need not be
>> verified before checking the poison during an alloc.
>>
>> Signed-off-by: Vinayak Menon <vinmenon@codeaurora.org>
>> ---
>>
>> Sending it as an RFC because I am not sure if I have missed a code path
>> that can free pages to buddy skipping kernel_poison_pages, making
>> the flag PAGE_EXT_DEBUG_POISON a necessity.
>>
> Have you tested this with hibernation? That's one place which tends
> to cause problems with poisoning.
Today I tried that on qemu and did not see any issue, and did not expect to hit any problems since
CONFIG_PAGE_POISONING_NO_SANITY gets enabled with HIBERNATION.
>
> I'm curious what issues you've caught with this patch.
This patch is used to catch corruptions during/soon after boot due to DDR instability. The free list can be
traversed in a dump and corrupted physical addresses can be analyzed for patterns. But I think, this
would also be useful in catching software induced corruptions which could be missed now because the page
has to undergo a cycle of alloc-free-alloc for any corruption to be detected. And on systems with more
RAM, it can take time for every page to complete this cycle.
Thanks,
Vinayak
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prev parent reply other threads:[~2017-03-07 14:08 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-03-06 14:16 Vinayak Menon
2017-03-06 23:17 ` Laura Abbott
2017-03-07 14:08 ` Vinayak Menon [this message]
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