From: Nick Piggin <npiggin@suse.de>
To: Christoph Hellwig <hch@infradead.org>
Cc: Jan Kara <jack@suse.cz>,
Andrew Morton <akpm@linux-foundation.org>,
LKML <linux-kernel@vger.kernel.org>,
fengguang.wu@intel.com
Subject: Re: [PATCH 2/3] mm: Implement writeback livelock avoidance using page tagging
Date: Tue, 16 Feb 2010 03:37:12 +1100 [thread overview]
Message-ID: <20100215163712.GV5723@laptop> (raw)
In-Reply-To: <20100215162453.GA6477@infradead.org>
On Mon, Feb 15, 2010 at 11:24:53AM -0500, Christoph Hellwig wrote:
> On Tue, Feb 16, 2010 at 03:21:27AM +1100, Nick Piggin wrote:
> > Also, I wonder what you think about leaving the tags dangling when
> > the loop bails out early? I have a *slight* concern about this
> > because previously we never have a tag set when radix_tree_delete
> > is called. I actually had a bug in that code in earlier versions
> > of rcu radix tree that only got found by the user test harness.
> > And another slight concern that it is just a bit ugly to leave the
> > tag. But I can accept that lower CPU overhead trumps ugliness :)
>
> The XFS inode cache calls radix_tree_delete with a tag set, and
> interestingly enough we're trying to catch a very weird bug in that
> area currently, which seems more or less directly related to the use
> of tags. But we also had a real locking bug related to tags, so I'm
> not yet sure what the issue is back until I hear back from the bug
> reported and reproducer.
Upon looking at the radix_tree_delete code again, the tag clearing
there seems rather simple so perhaps I misremembered some detail of
that bug I had.
next prev parent reply other threads:[~2010-02-15 16:37 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-02-11 23:06 [RFC] [PATCH 0/3] Writeback livelock avoidance using page tags (v2) Jan Kara
2010-02-11 23:06 ` [PATCH 1/3] radix-tree: Implement function radix_tree_gang_tag_if_tagged Jan Kara
2010-02-15 16:01 ` Nick Piggin
2010-02-11 23:06 ` [PATCH 2/3] mm: Implement writeback livelock avoidance using page tagging Jan Kara
2010-02-12 19:39 ` Andrew Morton
2010-02-15 15:47 ` Jan Kara
2010-02-15 16:21 ` Nick Piggin
2010-02-15 16:24 ` Christoph Hellwig
2010-02-15 16:37 ` Nick Piggin [this message]
2010-02-15 19:57 ` Jan Kara
2010-02-16 14:19 ` Nick Piggin
2010-02-11 23:06 ` [PATCH 3/3] mm: Debugging of new livelock avoidance Jan Kara
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=20100215163712.GV5723@laptop \
--to=npiggin@suse.de \
--cc=akpm@linux-foundation.org \
--cc=fengguang.wu@intel.com \
--cc=hch@infradead.org \
--cc=jack@suse.cz \
--cc=linux-kernel@vger.kernel.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 an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.