From: Christoph Hellwig <hch@infradead.org>
To: Nick Piggin <npiggin@suse.de>
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: Mon, 15 Feb 2010 11:24:53 -0500 [thread overview]
Message-ID: <20100215162453.GA6477@infradead.org> (raw)
In-Reply-To: <20100215162127.GU5723@laptop>
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.
next prev parent reply other threads:[~2010-02-15 16:24 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 [this message]
2010-02-15 16:37 ` Nick Piggin
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
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