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From: David Mosberger <davidm@napali.hpl.hp.com>
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Date: Mon, 9 Aug 2004 03:01:57 -0700
Subject: Re: copy_page_range()
In-Reply-To: <20040809092943.GP11200@holomorphy.com>
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Reply-To: davidm@hpl.hp.com
To: William Lee Irwin III <wli@holomorphy.com>
Cc: davidm@hpl.hp.com, "David S. Miller" <davem@redhat.com>, torvalds@osdl.org, linux-arch@vger.kernel.org
List-ID: <linux-arch.vger.kernel.org>

>>>>> On Mon, 9 Aug 2004 02:29:43 -0700, William Lee Irwin III <wli@holomorphy.com> said:

  William> On Mon, Aug 09, 2004 at 02:27:16AM -0700, David Mosberger
  William> wrote:
  >> Hmmh, for me, the single biggest stall seems to come from the
  >> pmd_none() check in free_one_pmd().

  William> That was the case in clear_page_tables(); it was
  William> copy_page_range() that saw mm->rss++ take an unusual amount
  William> of time.

Sorry, I misread your mail.  In my cause, the biggest staller in
copy_page_range() seems to be page_dup_rmap() (right after
dst->rss++).  Specifically, the test_and_set_bit() which comes from
page_dup_rmap()->page_map_lock()->bit_spin_lock() is causing the
stalls.

	--david