From: moore@free•fr (Chris Moore)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH v2] ARM: perf: ensure overflows aren't missed due to IRQ latency
Date: Sat, 26 Mar 2011 07:20:52 +0100 [thread overview]
Message-ID: <4D8D85C4.1080501@free.fr> (raw)
In-Reply-To: <1300986442-20461-1-git-send-email-will.deacon@arm.com>
Hi,
Sorry, my first attempt was regarded as suspicious.
This time I shall try to avoid HTML.
A couple of nitpicks in the introduction.
Le 24/03/2011 18:07, Will Deacon a ?crit :
> If a counter overflows during a perf stat profiling run it may overtake
> the last known value of the counter:
>
> 0 prev new 0xffffffff
> |----------|-------|----------------------|
>
> In this case, the number of events that have occurred is
> (0xffffffff - prev) + new. Unfortunately, the event update code will
> not realise an overflow has occurred and will instead report the event
> delta as (new - prev) which may be considerably smaller than the real
> count.
a) "(0xffffffff - prev) + new"
Surely that should be "(0x100000000 - prev) + new"
b) "may be considerably smaller"
I suggest either:
"will be 0x100000000 smaller (per overflow)"
or at least:
"will be considerably smaller"
That said, something like 2^32 would be more easily readable than 0x100000000.
Cheers,
Chris
next prev parent reply other threads:[~2011-03-26 6:20 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-03-24 17:07 [PATCH v2] ARM: perf: ensure overflows aren't missed due to IRQ latency Will Deacon
2011-03-25 16:08 ` Jamie Iles
2011-03-26 6:20 ` Chris Moore [this message]
2011-03-29 9:40 ` Will Deacon
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