From: Andi Kleen <andi@firstfloor.org>
To: Ingo Molnar <mingo@elte.hu>
Cc: Stefani Seibold <stefani@seibold.net>,
linux-kernel <linux-kernel@vger.kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
"H. Peter Anvin" <hpa@zytor.com>,
Americo Wang <xiyou.wangcong@gmail.com>,
Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [PATCH] RFC x86_64 more accurate KSTK_ESP implementation
Date: Sun, 08 Nov 2009 20:37:50 +0100 [thread overview]
Message-ID: <87639k7qpd.fsf@basil.nowhere.org> (raw)
In-Reply-To: <20091108113546.GN11372@elte.hu> (Ingo Molnar's message of "Sun, 8 Nov 2009 12:35:46 +0100")
Ingo Molnar <mingo@elte.hu> writes:
>
> I'd suggest a competely different method: why dont you use an IPI to
> sample the SP whenever someone wants to read it from /proc and we see
> that the task is running on a CPU right now?
Most of /proc tends to turn into a fast path when you run the right
monitoring tools unfortunately, which poll /proc at sometimes
quite high frequencies.
I suspect you'll slow something down significantly with this approach.
The only good way to avoid that would be to use a separate file, but again
if someone really wants it they can as well just use a ptrace()
based program from user space.
-Andi
--
ak@linux.intel.com -- Speaking for myself only.
next prev parent reply other threads:[~2009-11-08 19:37 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-11-03 7:31 [PATCH] update fix X86_64 procfs provide stack information for threads Stefani Seibold
2009-11-03 8:28 ` Ingo Molnar
2009-11-03 9:06 ` Stefani Seibold
2009-11-03 18:16 ` Ingo Molnar
2009-11-05 8:19 ` [PATCH] RFC x86_64 more accurate KSTK_ESP implementation Stefani Seibold
2009-11-05 11:08 ` Andi Kleen
2009-11-05 12:11 ` Stefani Seibold
2009-11-08 11:35 ` Ingo Molnar
2009-11-08 12:51 ` Stefani Seibold
2009-11-08 12:55 ` Ingo Molnar
2009-11-08 14:00 ` Stefani Seibold
2009-11-08 16:34 ` H. Peter Anvin
2009-11-08 19:37 ` Andi Kleen [this message]
2009-11-05 13:02 ` [PATCH] fix /proc/<pid>/stat stack pointer for kernel threads Stefani Seibold
2009-11-13 8:01 ` [tip:x86/urgent] fs: " Stefani Seibold
2009-11-04 11:17 ` [PATCH] update fix X86_64 procfs provide stack information for threads Andi Kleen
2009-11-04 11:50 ` Stefani Seibold
2009-11-04 12:00 ` Andi Kleen
2009-11-04 12:22 ` Stefani Seibold
2009-11-04 15:42 ` Stefani Seibold
2009-11-04 22:21 ` Stefani Seibold
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