From: Robert Love <rml@tech9.net> To: linux-kernel@vger.kernel.org Subject: Re: [PATCH] update: preemptive kernel for O(1) sched Date: 13 Jan 2002 23:34:43 -0500 Cc: kpreempt-tech@lists.sourceforge.net A version of preempt-stats for the 2.5 series kernel is available at: ftp://ftp.kernel.org/pub/linux/kernel/people/rml/preempt-stats and your favorite mirror. Patches for 2.4 are available, too. This patch, used on top of preempt-kernel, allows the measuring of periods of non-preemptible so that we can identify long-held locks. The patch creates a proc entry, latencytimes, which contains the top 20 worst-case recorded periods since it was last read. To begin recording, read the file once. Subsequent reads will return the results. I.e., [23:25:08]rml@langston:~$ cat /proc/latencytimes Worst 20 latency times of 277 measured in this period. usec cause mask start line/file address end line/file 9982 spin_lock 0 488/sched.c c0117ee2 645/irq.c 968 BKL 0 666/tty_io.c c0193d58 645/irq.c 430 spin_lock 0 69/i387.c c010f34f 96/mmx.c 103 ide0 0 583/irq.c c010ab1c 645/irq.c 100 BKL 0 2562/buffer.c c014abda 2565/buffer.c 54 BKL 0 702/tty_io.c c019406b 704/tty_io.c ... etc The goal would be to identity the problem areas and fix them. Robert Love - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/