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References: <84c7f26182b7f4723c0fe3b34ba912a9de92b8b7.1502758114.git.tim.c.chen@linux.intel.com>
 <CA+55aFznC1wqBSfYr8=92LGqz5-F6fHMzdXoqM4aOYx8sT1Dhg@mail.gmail.com> <37D7C6CF3E00A74B8858931C1DB2F07753786CE9@SHSMSX103.ccr.corp.intel.com>
From: Linus Torvalds <torvalds@linux-foundation.org>
Date: Thu, 17 Aug 2017 09:25:08 -0700
Message-ID: <CA+55aFwzTMrZwh7TE_VeZt8gx5Syoop-kA=Xqs56=FkyakrM6g@mail.gmail.com>
Subject: Re: [PATCH 1/2] sched/wait: Break up long wake list walk
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Sender: owner-linux-mm@kvack.org
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To: "Liang, Kan" <kan.liang@intel.com>
Cc: Tim Chen <tim.c.chen@linux.intel.com>, Peter Zijlstra <peterz@infradead.org>, Ingo Molnar <mingo@elte.hu>, Andi Kleen <ak@linux.intel.com>, Andrew Morton <akpm@linux-foundation.org>, Johannes Weiner <hannes@cmpxchg.org>, Jan Kara <jack@suse.cz>, linux-mm <linux-mm@kvack.org>, Linux Kernel Mailing List <linux-kernel@vger.kernel.org>

On Thu, Aug 17, 2017 at 9:17 AM, Liang, Kan <kan.liang@intel.com> wrote:
>
> We tried both 12 and 16 bit table and that didn't make a difference.
> The long wake ups are mostly on the same page when we do instrumentation

Ok.

> Here is the wake_up_page_bit call stack when the workaround is running, which
> is collected by perf record -g -a -e probe:wake_up_page_bit -- sleep 10

It's actually not really wake_up_page_bit() that is all that
interesting, it would be more interesting to see which path it is that
*adds* the entries.

So it's mainly wait_on_page_bit_common(), but also add_page_wait_queue().

Can you get that call stack instead (or in addition to)?

                  Linus

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