From: Ingo Molnar <mingo@elte.hu>
To: Mark_H_Johnson@raytheon.com
Cc: Amit Shah <amit.shah@codito.com>,
Karsten Wiese <annabellesgarden@yahoo.de>,
Bill Huey <bhuey@lnxw.com>, Adam Heath <doogie@debian.org>,
emann@mrv.com, Gunther Persoons <gunther_persoons@spymac.com>,
"K.R. Foley" <kr@cybsft.com>,
linux-kernel@vger.kernel.org,
Florian Schmidt <mista.tapas@gmx.net>,
Fernando Pablo Lopez-Lezcano <nando@ccrma.Stanford.EDU>,
Lee Revell <rlrevell@joe-job.com>,
Rui Nuno Capela <rncbc@rncbc.org>,
Shane Shrybman <shrybman@aei.ca>,
Esben Nielsen <simlo@phys.au.dk>,
Thomas Gleixner <tglx@linutronix.de>,
Michal Schmidt <xschmi00@stud.feec.vutbr.cz>
Subject: [patch] Real-Time Preemption, -RT-2.6.10-rc2-mm3-V0.7.32-15
Date: Fri, 10 Dec 2004 11:53:52 +0100 [thread overview]
Message-ID: <20041210105352.GA4749@elte.hu> (raw)
In-Reply-To: <20041209225555.GA31588@elte.hu>
* Ingo Molnar <mingo@elte.hu> wrote:
> this smells too. [...]
found two brown-paperbag bugs that caused bad latencies in the -RT
kernel: when i added PREEMPT_DIRECT (which first showed up in -32-10) i
also added a missed-reschedule bug to try_to_wake_up() and to
mutex/semaphore-unlock (__up()). Oops.
i dont think this bug could explain a msec-range latency because the
syscall return path should catch the missed reschedule and it would need
continuous syscall execution in the milliseconds range by a lowprio task
for a latency to be transported to latencytest, but certainly the bug
doesnt help latencies. The -32-15 kernel can be downloaded from the
usual place:
http://redhat.com/~mingo/realtime-preempt/
other changes in -32-15: more work on the tracer, cleaner trace output
and the tracing of syscall entries and returns, with arguments and
return values displayed as well (i.e. a simple strace variant). Here is
how a syscall now looks like in /proc/latency_trace:
loop-tes-3885 0.... 100µs > sys_getppid (002fcffc 00000001 0000007b)
loop-tes-3885 0.... 101µs+: sys_getppid (sysenter_past_esp)
loop-tes-3885 0d... 103µs < (3868)
'< (return-val)' is the syscall return value, '> sys_name(params)' is
the syscall itself. (note that the return path is also used by
interrupts, so it's not purely a syscall-return point) This makes it
easier to track userspace execution.
Ingo
next prev parent reply other threads:[~2004-12-10 10:54 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-12-09 21:58 [patch] Real-Time Preemption, -RT-2.6.10-rc2-mm3-V0.7.32-6 Mark_H_Johnson
2004-12-09 22:55 ` Ingo Molnar
2004-12-10 10:53 ` Ingo Molnar [this message]
2004-12-10 14:59 ` [patch] Real-Time Preemption, -RT-2.6.10-rc2-mm3-V0.7.32-15 Gene Heskett
2004-12-10 15:59 ` Gene Heskett
2004-12-10 19:09 ` Lee Revell
2004-12-10 17:49 Mark_H_Johnson
2004-12-10 21:09 ` Ingo Molnar
2004-12-10 21:12 ` Ingo Molnar
2004-12-10 21:24 ` Ingo Molnar
2004-12-13 0:16 ` Fernando Lopez-Lezcano
2004-12-13 6:47 ` Ingo Molnar
2004-12-14 0:46 ` Fernando Lopez-Lezcano
2004-12-14 4:42 ` K.R. Foley
2004-12-14 8:47 ` Rui Nuno Capela
2004-12-14 11:35 ` Ingo Molnar
2004-12-10 20:03 Mark_H_Johnson
2004-12-10 21:06 Mark_H_Johnson
2004-12-10 21:40 ` Ingo Molnar
2004-12-10 21:31 Mark_H_Johnson
2004-12-10 21:54 ` Ingo Molnar
2004-12-10 21:54 Mark_H_Johnson
2004-12-10 22:14 ` Ingo Molnar
2004-12-10 21:58 Mark_H_Johnson
2004-12-10 22:06 Mark_H_Johnson
2004-12-10 22:24 ` Ingo Molnar
2004-12-13 17:05 Mark_H_Johnson
2004-12-13 22:33 ` Ingo Molnar
2004-12-13 20:02 Mark_H_Johnson
2004-12-13 22:39 ` Ingo Molnar
2004-12-13 23:14 Mark_H_Johnson
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