linux-kernel - Re: [PATCH 1/4] x86, mm: Trace when an IPI is about to be sent

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Date:	Thu, 16 Apr 2015 18:39:48 +0100
From:	Mel Gorman <mgorman@...e.de>
To:	Dave Hansen <dave.hansen@...el.com>
Cc:	Linux-MM <linux-mm@...ck.org>, Rik van Riel <riel@...hat.com>,
	Hugh Dickins <hughd@...gle.com>,
	Minchan Kim <minchan@...nel.org>,
	Andi Kleen <andi@...stfloor.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/4] x86, mm: Trace when an IPI is about to be sent

On Thu, Apr 16, 2015 at 09:55:43AM -0700, Dave Hansen wrote:
> On 04/16/2015 03:22 AM, Mel Gorman wrote:
> > It is easy to trace when an IPI is received to flush a TLB but harder to
> > detect what event sent it. This patch makes it easy to identify the source
> > of IPIs being transmitted for TLB flushes on x86.
> 
> Looks fine to me.  I think I even thought about adding this but didn't
> see an immediate need for it.  I guess this does let you see how many
> IPIs are sent vs. received.
> 

It would but that's not why I wanted it. I wanted a stack track of who
was sending the IPI and I can't get that on the receive side. I could
have used perf probe and some hackery but this seemed useful in itself.

> Reviewed-by: Dave Hansen <dave.hansen@...el.com>

Thanks.

-- 
Mel Gorman
SUSE Labs
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