From: Ingo Molnar <mingo@kernel.org>
To: Don Zickus <dzickus@redhat.com>
Cc: x86@kernel.org, "Peter Zijlstra" <peterz@infradead.org>,
ak@linux.intel.com, gong.chen@linux.intel.com,
LKML <linux-kernel@vger.kernel.org>,
"Thomas Gleixner" <tglx@linutronix.de>,
"Frédéric Weisbecker" <fweisbec@gmail.com>,
"Steven Rostedt" <rostedt@goodmis.org>
Subject: Re: [PATCH 1/5] x86, nmi: Add new nmi type 'external'
Date: Wed, 7 May 2014 17:38:54 +0200 [thread overview]
Message-ID: <20140507153854.GA14926@gmail.com> (raw)
In-Reply-To: <1399476883-98970-2-git-send-email-dzickus@redhat.com>
* Don Zickus <dzickus@redhat.com> wrote:
> I noticed when debugging a perf problem on a machine with GHES enabled,
> perf seemed slow. I then realized that the GHES NMI routine was taking
> a global lock all the time to inspect the hardware. This contended
> with all the local perf counters which did not need a lock. So each cpu
> accidentally was synchronizing with itself when using perf.
>
> This is because the way the nmi handler works. It executes all the handlers
> registered to a particular subtype (to deal with nmi sharing). As a result
> the GHES handler was executed on every PMI.
>
> Fix this by creating a new nmi type called NMI_EXT, which is used by
> handlers that need to probe external hardware and require a global lock
> to do so.
>
> Now the main NMI handler can check the internal NMI handlers first and
> then the external ones if nothing is found.
>
> This makes perf a little faster again on those machines with GHES enabled.
So what happens if GHES asserts an NMI at the same time a PMI
triggers?
If the perf PMI executes and indicates that it has handled something,
we don't execute the GHES handler, right? Will the GHES re-trigger the
NMI after we return?
Thanks,
Ingo
next prev parent reply other threads:[~2014-05-07 15:39 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-05-07 15:34 [PATCH 0/5 RESEND] x86, nmi: Various fixes and cleanups Don Zickus
2014-05-07 15:34 ` [PATCH 1/5] x86, nmi: Add new nmi type 'external' Don Zickus
2014-05-07 15:38 ` Ingo Molnar [this message]
2014-05-07 16:02 ` Don Zickus
2014-05-07 16:27 ` Ingo Molnar
2014-05-07 16:48 ` Don Zickus
2014-05-08 16:33 ` Don Zickus
2014-05-08 17:35 ` Ingo Molnar
2014-05-08 17:52 ` Don Zickus
2014-05-09 7:10 ` Ingo Molnar
2014-05-09 13:36 ` Don Zickus
2014-05-07 15:34 ` [PATCH 2/5] x86, nmi: Add boot line option 'panic_on_unrecovered_nmi' and 'panic_on_io_nmi' Don Zickus
2014-05-07 15:34 ` [PATCH 3/5] x86, nmi: Remove 'reason' value from unknown nmi output Don Zickus
2014-05-07 15:34 ` [PATCH 4/5] x86, nmi: Move default external NMI handler to its own routine Don Zickus
2014-05-07 15:34 ` [PATCH 5/5] x86, nmi: Add better NMI stats to /proc/interrupts and show handlers Don Zickus
2014-05-07 15:42 ` Ingo Molnar
2014-05-07 16:04 ` Don Zickus
2014-05-07 16:30 ` Ingo Molnar
2014-05-07 19:50 ` Elliott, Robert (Server Storage)
2014-05-08 1:28 ` Don Zickus
2014-05-08 6:04 ` Ingo Molnar
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