From: Luis Henriques <lhenriques@suse.com>
To: Tejun Heo <tj@kernel.org>
Cc: Dennis Zhou <dennisszhou@gmail.com>,
Christoph Lameter <cl@linux.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/2] percpu: fix iteration to prevent skipping over block
Date: Thu, 28 Sep 2017 09:31:00 +0100 [thread overview]
Message-ID: <87lgkzkywr.fsf@hermes> (raw)
In-Reply-To: <20170927215125.GB15129@devbig577.frc2.facebook.com> (Tejun Heo's message of "Wed, 27 Sep 2017 14:51:25 -0700")
Tejun Heo <tj@kernel.org> writes:
> On Wed, Sep 27, 2017 at 04:35:00PM -0500, Dennis Zhou wrote:
>> The iterator functions pcpu_next_md_free_region and
>> pcpu_next_fit_region use the block offset to determine if they have
>> checked the area in the prior iteration. However, this causes an issue
>> when the block offset is greater than subsequent block contig hints. If
>> within the iterator it moves to check subsequent blocks, it may fail in
>> the second predicate due to the block offset not being cleared. Thus,
>> this causes the allocator to skip over blocks leading to false failures
>> when allocating from the reserved chunk. While this happens in the
>> general case as well, it will only fail if it cannot allocate a new
>> chunk.
>>
>> This patch resets the block offset to 0 to pass the second predicate
>> when checking subseqent blocks within the iterator function.
>>
>> Signed-off-by: Dennis Zhou <dennisszhou@gmail.com>
>> Reported-by: Luis Henriques <lhenriques@suse.com>
>
> Luis, can you please verify that this fixes the allocaiton failure you
> were seeing?
I can confirm that I'm no longer seeing the allocation failure after
applying these patches. Feel free to add my:
Tested-by: Luis Henriques <lhenriques@suse.com>
Cheers,
--
Luis
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WARNING: multiple messages have this Message-ID (diff)
From: Luis Henriques <lhenriques@suse.com>
To: Tejun Heo <tj@kernel.org>
Cc: Dennis Zhou <dennisszhou@gmail.com>,
Christoph Lameter <cl@linux.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/2] percpu: fix iteration to prevent skipping over block
Date: Thu, 28 Sep 2017 09:31:00 +0100 [thread overview]
Message-ID: <87lgkzkywr.fsf@hermes> (raw)
In-Reply-To: <20170927215125.GB15129@devbig577.frc2.facebook.com> (Tejun Heo's message of "Wed, 27 Sep 2017 14:51:25 -0700")
Tejun Heo <tj@kernel.org> writes:
> On Wed, Sep 27, 2017 at 04:35:00PM -0500, Dennis Zhou wrote:
>> The iterator functions pcpu_next_md_free_region and
>> pcpu_next_fit_region use the block offset to determine if they have
>> checked the area in the prior iteration. However, this causes an issue
>> when the block offset is greater than subsequent block contig hints. If
>> within the iterator it moves to check subsequent blocks, it may fail in
>> the second predicate due to the block offset not being cleared. Thus,
>> this causes the allocator to skip over blocks leading to false failures
>> when allocating from the reserved chunk. While this happens in the
>> general case as well, it will only fail if it cannot allocate a new
>> chunk.
>>
>> This patch resets the block offset to 0 to pass the second predicate
>> when checking subseqent blocks within the iterator function.
>>
>> Signed-off-by: Dennis Zhou <dennisszhou@gmail.com>
>> Reported-by: Luis Henriques <lhenriques@suse.com>
>
> Luis, can you please verify that this fixes the allocaiton failure you
> were seeing?
I can confirm that I'm no longer seeing the allocation failure after
applying these patches. Feel free to add my:
Tested-by: Luis Henriques <lhenriques@suse.com>
Cheers,
--
Luis
next prev parent reply other threads:[~2017-09-28 8:31 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-09-27 21:34 [PATCH 0/2] percpu: fix block iterators and reserved chunk stats Dennis Zhou
2017-09-27 21:34 ` Dennis Zhou
2017-09-27 21:34 ` [PATCH 1/2] percpu: fix starting offset for chunk statistics traversal Dennis Zhou
2017-09-27 21:34 ` Dennis Zhou
2017-09-27 21:46 ` Tejun Heo
2017-09-27 21:46 ` Tejun Heo
2017-09-27 21:35 ` [PATCH 2/2] percpu: fix iteration to prevent skipping over block Dennis Zhou
2017-09-27 21:35 ` Dennis Zhou
2017-09-27 21:51 ` Tejun Heo
2017-09-27 21:51 ` Tejun Heo
2017-09-28 8:31 ` Luis Henriques [this message]
2017-09-28 8:31 ` Luis Henriques
2017-09-28 14:40 ` Tejun Heo
2017-09-28 14:40 ` Tejun Heo
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