On Thu, 2010-07-01 at 16:55 -0500, Timur Tabi wrote: > On Tue, Jun 29, 2010 at 2:54 PM, Timur Tabi <[email protected]> wrote: > > I'm adding support for a new e500-based board (the P1022DS), and in > > the process I've discovered that enabling CONFIG_NO_HZ (Tickless > > System / Dynamic Ticks) causes significant responsiveness problems on > > the serial console. When I type on the console, I see delays of up to > > a half-second for almost every character. It acts as if there's a > > background process eating all the CPU. > > I finally finished my git-bisect, and it wasn't that helpful. I had > to skip several commits because the kernel just wouldn't boot: > > There are only 'skip'ped commits left to test. > The first bad commit could be any of: > 6bc6cf2b61336ed0c55a615eb4c0c8ed5daf3f08 > 8b911acdf08477c059d1c36c21113ab1696c612b > 21406928afe43f1db6acab4931bb8c886f4d04ce > 5ca9880c6f4ba4c84b517bc2fed5366adf63d191 > a64692a3afd85fe048551ab89142fd5ca99a0dbd > f2e74eeac03ffb779d64b66a643c5e598145a28b > c6ee36c423c3ed1fb86bb3eabba9fc256a300d16 > e12f31d3e5d36328c7fbd0fce40a95e70b59152c > 13814d42e45dfbe845a0bbe5184565d9236896ae > b42e0c41a422a212ddea0666d5a3a0e3c35206db > 39c0cbe2150cbd848a25ba6cdb271d1ad46818ad <== the crime scene > beac4c7e4a1cc6d57801f690e5e82fa2c9c245c8 > 41acab8851a0408c1d5ad6c21a07456f88b54d40 > 6427462bfa50f50dc6c088c07037264fcc73eca1 > c9494727cf293ae2ec66af57547a3e79c724fec2 > We cannot bisect more! > > These correspond to a batch of scheduler patches, most from Mike Galbraith. > > I don't know what to do now. I can't test any of these commits. Even > if I could, they look like they're all part of one set, so I doubt I > could narrow it down to one commit anyway.
Hi Timur, This has already fixed. Below is the final fix from tip. commit 3310d4d38fbc514e7b18bd3b1eea8effdd63b5aa Author: Peter Zijlstra <[email protected]> Date: Thu Jun 17 18:02:37 2010 +0200 nohz: Fix nohz ratelimit Chris Wedgwood reports that 39c0cbe (sched: Rate-limit nohz) causes a serial console regression, unresponsiveness, and indeed it does. The reason is that the nohz code is skipped even when the tick was already stopped before the nohz_ratelimit(cpu) condition changed. Move the nohz_ratelimit() check to the other conditions which prevent long idle sleeps. Reported-by: Chris Wedgwood <[email protected]> Tested-by: Brian Bloniarz <[email protected]> Signed-off-by: Mike Galbraith <[email protected]> Signed-off-by: Peter Zijlstra <[email protected]> Cc: Jiri Kosina <[email protected]> Cc: Linus Torvalds <[email protected]> Cc: Greg KH <[email protected]> Cc: Alan Cox <[email protected]> Cc: OGAWA Hirofumi <[email protected]> Cc: Jef Driesen <[email protected]> LKML-Reference: <1276790557.27822.516.ca...@twins> Signed-off-by: Thomas Gleixner <[email protected]> diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c index 1d7b9bc..783fbad 100644 --- a/kernel/time/tick-sched.c +++ b/kernel/time/tick-sched.c @@ -315,9 +315,6 @@ void tick_nohz_stop_sched_tick(int inidle) goto end; } - if (nohz_ratelimit(cpu)) - goto end; - ts->idle_calls++; /* Read jiffies and the time when jiffies were updated last */ do { @@ -328,7 +325,7 @@ void tick_nohz_stop_sched_tick(int inidle) } while (read_seqretry(&xtime_lock, seq)); if (rcu_needs_cpu(cpu) || printk_needs_cpu(cpu) || - arch_needs_cpu(cpu)) { + arch_needs_cpu(cpu) || nohz_ratelimit(cpu)) { next_jiffies = last_jiffies + 1; delta_jiffies = 1; } else { _______________________________________________ Linuxppc-dev mailing list [email protected] https://lists.ozlabs.org/listinfo/linuxppc-dev
