linux-mm.kvack.org archive mirror
 help / color / mirror / Atom feed
From: Christopher Lameter <cl@linux.com>
To: Matthew Wilcox <willy@infradead.org>
Cc: Michal Hocko <mhocko@kernel.org>,
	Vlastimil Babka <vbabka@suse.cz>,
	 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>,
	Ming Lei <ming.lei@redhat.com>,
	 Dave Chinner <david@fromorbit.com>,
	 "Darrick J . Wong" <darrick.wong@oracle.com>,
	 Christoph Hellwig <hch@lst.de>,
	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: Tue, 3 Sep 2019 20:13:45 +0000	[thread overview]
Message-ID: <0100016cf8c3033d-bbcc9ba3-2d59-4654-a7c2-8ba094f8a7de-000000@email.amazonses.com> (raw)
In-Reply-To: <20190901005205.GA2431@bombadil.infradead.org>

On Sat, 31 Aug 2019, Matthew Wilcox wrote:

> > The current behavior without special alignment for these caches has been
> > in the wild for over a decade. And this is now coming up?
>
> In the wild ... and rarely enabled.  When it is enabled, it may or may
> not be noticed as data corruption, or tripping other debugging asserts.
> Users then turn off the rare debugging option.

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.

> > If there is an exceptional alignment requirement then that needs to be
> > communicated to the allocator. A special flag or create a special
> > kmem_cache or something.
>
> The only way I'd agree to that is if we deliberately misalign every
> allocation that doesn't have this special flag set.  Because right now,
> breakage happens everywhere when these debug options are enabled, and
> the very people who need to be helped are being hurt by the debugging.

That is customarily occurring for testing by adding "slub_debug" to the
kernel commandline (or adding debug kernel options) and since my
information is that this is done frequently (and has been for over a
decade now) I am having a hard time believing the stories of great
breakage here. These drivers were not tested with debugging on before?
Never ran with a debug kernel?


  reply	other threads:[~2019-09-03 20:13 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 [this message]
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
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

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=0100016cf8c3033d-bbcc9ba3-2d59-4654-a7c2-8ba094f8a7de-000000@email.amazonses.com \
    --to=cl@linux.com \
    --cc=James.Bottomley@hansenpartnership.com \
    --cc=akpm@linux-foundation.org \
    --cc=darrick.wong@oracle.com \
    --cc=david@fromorbit.com \
    --cc=hch@lst.de \
    --cc=linux-block@vger.kernel.org \
    --cc=linux-btrfs@vger.kernel.org \
    --cc=linux-fsdevel@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-mm@kvack.org \
    --cc=linux-xfs@vger.kernel.org \
    --cc=mhocko@kernel.org \
    --cc=ming.lei@redhat.com \
    --cc=penberg@kernel.org \
    --cc=rientjes@google.com \
    --cc=vbabka@suse.cz \
    --cc=willy@infradead.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).