Date: Mon, 12 Apr 2004 14:12:44 -0700
From: Andrew Morton <akpm@osdl.org>
To: "Martin J. Bligh" <mbligh@aracnet.com>
Cc: vrajesh@umich.edu, hugh@veritas.com, andrea@suse.de,
       linux-kernel@vger.kernel.org
Subject: Re: [PATCH] anobjrmap 9 priority mjb tree
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"Martin J. Bligh" <mbligh@aracnet.com> wrote:
>
> Turns out he'd turned the
> locking in find_get_page from "spin_lock(&mapping->page_lock)" into
> "spin_lock_irq(&mapping->tree_lock)",

That's from the use-radix-tree-walks-for-writeback code.

Use oprofile - it's NMI-based.

> and I'm using readprofile, which
> doesn't profile with irqs off, so it's not really disappeared, just hidden.
> Not sure which sub-patch that comes from, and it turned out to be a bit of
> a dead end, but whilst I'm there, I thought I'd point out this was contended,
> and show the diffprofile with and without spinline for aa5:
> 
>      22210  246777.8% find_trylock_page
>       2538    36.4% atomic_dec_and_lock

profiler brokenness, surely.  Almost nothing calls find_trylock_page(),
unless Andrea has done something peculiar.  Use oprofile.
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