From: Ingo Molnar <mingo@kernel.org>
To: Andi Kleen <andi@firstfloor.org>
Cc: "H. Peter Anvin" <hpa@linux.intel.com>,
Steven Rostedt <rostedt@goodmis.org>,
LKML <linux-kernel@vger.kernel.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Thomas Gleixner <tglx@linutronix.de>,
Peter Zijlstra <peterz@infradead.org>,
Clark Williams <williams@redhat.com>,
Borislav Petkov <bp@alien8.de>,
Andrew Morton <akpm@linux-foundation.org>,
"Kleen, Andi" <andi.kleen@intel.com>
Subject: Re: [RFC][PATCH] x86: Lazy disabling of interrupts
Date: Thu, 10 Oct 2013 06:53:09 +0200 [thread overview]
Message-ID: <20131010045309.GB23267@gmail.com> (raw)
In-Reply-To: <878uy2ytd8.fsf@tassilo.jf.intel.com>
* Andi Kleen <andi@firstfloor.org> wrote:
> - That said, I think a software CLI/STI is somewhat useful for
> profiling, as it can allow to measure how long interrupts are delayed by
> CLI/STI. [...]
That could be measured directly in a simpler way, without disrupting
CLI/STI: by turning all IRQs into NMIs and resending them from a special
NMI handler. (and of course timestamping the NMI arrival time and the IRQ
entry time so that instrumentation can recover it.)
If indirect, statistical measurement suffices then IRQ delivery latencies
can also be estimated statistically without any kernel changes: by
profiling IRQ disable/enable sections (there's a counter for that),
calculating average IRQ-disable section length from that. The average IRQ
delay will be 50% of that value, assuming normal distribution of IRQs.
This should be good enough for most cases.
Thanks,
Ingo
next prev parent reply other threads:[~2013-10-10 4:53 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20131009144150.108f7041@gandalf.local.home>
2013-10-09 20:45 ` [RFC][PATCH] x86: Lazy disabling of interrupts H. Peter Anvin
2013-10-09 22:25 ` Andi Kleen
2013-10-10 0:36 ` Steven Rostedt
2013-10-10 3:39 ` David Miller
2013-10-10 3:54 ` Steven Rostedt
2013-10-10 4:53 ` Ingo Molnar [this message]
[not found] ` <20131010001153.1f171bff@gandalf.local.home>
2013-10-10 4:19 ` David Miller
2013-10-10 9:03 ` Borislav Petkov
2013-10-10 12:30 ` Steven Rostedt
2013-10-10 13:40 ` Borislav Petkov
2013-10-10 12:27 Steven Rostedt <rostedt@goodmis.org> (by way of Steven Rostedt <rostedt@goodmis.org>) (by way of Steven Rostedt
2013-10-10 14:45 ` anish singh
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