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From: Vlastimil Babka <vbabka@suse.cz>
To: Ming Lei <ming.lei@redhat.com>, Christoph Hellwig <hch@lst.de>
Cc: Matthew Wilcox <willy@infradead.org>,
	Christopher Lameter <cl@linux.com>,
	Michal Hocko <mhocko@kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	linux-mm@kvack.org, linux-kernel@vger.kernel.org,
	Pekka Enberg <penberg@kernel.org>,
	David Rientjes <rientjes@google.com>,
	Dave Chinner <david@fromorbit.com>,
	"Darrick J . Wong" <darrick.wong@oracle.com>,
	linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org,
	linux-block@vger.kernel.org,
	James Bottomley <James.Bottomley@hansenpartnership.com>,
	linux-btrfs@vger.kernel.org
Subject: Re: [PATCH v2 2/2] mm, sl[aou]b: guarantee natural alignment for kmalloc(power-of-two)
Date: Wed, 4 Sep 2019 09:20:03 +0200	[thread overview]
Message-ID: <54e82c0d-aedc-3976-4b29-4f669ac59cae@suse.cz> (raw)
In-Reply-To: <20190904064043.GA7578@ming.t460p>

On 9/4/19 8:40 AM, Ming Lei wrote:
> On Wed, Sep 04, 2019 at 07:19:33AM +0200, Christoph Hellwig wrote:
>> On Tue, Sep 03, 2019 at 01:53:12PM -0700, Matthew Wilcox wrote:
>>>> Its enabled in all full debug session as far as I know. Fedora for
>>>> example has been running this for ages to find breakage in device drivers
>>>> etc etc.
>>>
>>> Are you telling me nobody uses the ramdisk driver on fedora?  Because
>>> that's one of the affected drivers.
>>
>> For pmem/brd misaligned memory alone doesn't seem to be the problem.
>> Misaligned memory that cross a page barrier is.  And at least XFS
>> before my log recovery changes only used kmalloc for smaller than
>> page size allocation, so this case probably didn't hit.
> 
> BTW, does sl[aou]b guarantee that smaller than page size allocation via kmalloc()
> won't cross page boundary any time?

AFAIK no, it's the same as with the alignment. After this patch, that
guarantee would follow from the alignment one for power of two sizes,
but sizes 96 and 192 could still cross page boundary.

> Thanks,
> Ming
> 



  reply	other threads:[~2019-09-04  7:20 UTC|newest]

Thread overview: 40+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-26 11:16 [PATCH v2 0/2] guarantee natural alignment for kmalloc() Vlastimil Babka
2019-08-26 11:16 ` [PATCH v2 1/2] mm, sl[ou]b: improve memory accounting Vlastimil Babka
2019-08-26 11:16 ` [PATCH v2 2/2] mm, sl[aou]b: guarantee natural alignment for kmalloc(power-of-two) Vlastimil Babka
2019-08-28 18:45   ` Christopher Lameter
2019-08-28 19:46     ` Matthew Wilcox
2019-08-28 22:24       ` Dave Chinner
2019-08-29  7:56         ` Vlastimil Babka
2019-08-30  0:29           ` Dave Chinner
2019-08-29  7:39       ` Michal Hocko
2019-08-30 17:41         ` Christopher Lameter
2019-09-01  0:52           ` Matthew Wilcox
2019-09-03 20:13             ` Christopher Lameter
2019-09-03 20:53               ` Matthew Wilcox
2019-09-04  5:19                 ` Christoph Hellwig
2019-09-04  6:40                   ` Ming Lei
2019-09-04  7:20                     ` Vlastimil Babka [this message]
2019-09-04 19:31                 ` Christopher Lameter
2019-09-23 16:36   ` Vlastimil Babka
2019-09-23 17:17     ` David Sterba
2019-09-23 17:51       ` Darrick J. Wong
2019-09-24 20:47         ` cl
2019-09-24 20:51           ` Matthew Wilcox
2019-09-24 20:55             ` cl
2019-09-26 13:02               ` David Sterba
2019-09-24 21:19         ` Vlastimil Babka
2019-09-24 21:53           ` Dave Chinner
2019-09-24 22:21             ` Darrick J. Wong
2019-09-24 20:52       ` cl
2019-09-24 23:54         ` Andrew Morton
2019-09-25  7:17           ` Vlastimil Babka
2019-09-26  0:16             ` Christopher Lameter
2019-09-26  0:14           ` Christopher Lameter
2019-09-26  7:41             ` Vlastimil Babka
2019-09-28  1:12               ` Christopher Lameter
2019-09-30 13:32                 ` Matthew Wilcox
2019-09-23 17:54     ` Roman Gushchin
2019-09-30  8:06     ` Christoph Hellwig
2019-09-30  9:23     ` Michal Hocko
2019-09-30  9:32       ` Kirill A. Shutemov
2019-09-23 18:57   ` Matthew Wilcox

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