From: Al Viro <viro@ZenIV.linux.org.uk>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org
Subject: Re: [git pull] vfs.git bits and pieces
Date: Wed, 20 Nov 2013 17:47:12 +0000 [thread overview]
Message-ID: <20131120174712.GG10323@ZenIV.linux.org.uk> (raw)
In-Reply-To: <20131120174211.GF10323@ZenIV.linux.org.uk>
On Wed, Nov 20, 2013 at 05:42:11PM +0000, Al Viro wrote:
> [Apologies for delay; I'd spent the last day hunting down something that
> turned out to be a VM leak completely unrelated to this stuff - it's
> present in mainline, for starters. Unreliable reproducers make for fun
> bisects ;-/ Anyway, by now I'm absolutely sure that this is a VM bug and
> not something I had somehow managed to break, so...]
BTW, something odd happened to mm/memory.c - either a mangled patch
or a lost followup. Take a look at the last commit in there:
commit ea1e7ed33708c7a760419ff9ded0a6cb90586a50
Author: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Date: Thu Nov 14 14:31:53 2013 -0800
mm: create a separate slab for page->ptl allocation
If DEBUG_SPINLOCK and DEBUG_LOCK_ALLOC are enabled spinlock_t on x86_64
is 72 bytes. For page->ptl they will be allocated from kmalloc-96 slab,
so we loose 24 on each. An average system can easily allocate few tens
thousands of page->ptl and overhead is significant.
Let's create a separate slab for page->ptl allocation to solve this.
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Fair enough, and yes, it does create that separate slab. The problem is,
it's still using kmalloc/kfree for those beasts - page_ptl_cachep isn't
used at all...
next prev parent reply other threads:[~2013-11-20 17:47 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-11-20 17:42 [git pull] vfs.git bits and pieces Al Viro
2013-11-20 17:47 ` Al Viro [this message]
2013-11-20 22:16 ` Al Viro
2013-11-20 22:24 ` Joe Perches
2013-11-20 22:33 ` Linus Torvalds
2013-11-20 22:40 ` Andrew Morton
2013-11-21 11:19 ` Kirill A. Shutemov
2013-11-20 22:42 ` Damien Wyart
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=20131120174712.GG10323@ZenIV.linux.org.uk \
--to=viro@zeniv.linux.org.uk \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=torvalds@linux-foundation.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).