Re: CONFIG_NO_HZ causing poor console responsiveness
On Tue, Jun 29, 2010 at 02:54:17PM -0500, Timur Tabi 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 don't have time to debug this thoroughly at the moment. The problem > occurs in the latest kernel, but it appears not to occur in 2.6.32. > > Has anyone else seen anything like this? Yes, with a P2020RDB and kernel 2.6.35-rc1. Serial console is really slow on an otherwise idle machine. I assumed it was a hardware problem. Richard ___ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
Re: CONFIG_NO_HZ causing poor console responsiveness
On Tue, Jun 29, 2010 at 2:54 PM, Timur Tabi 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 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. -- Timur Tabi Linux kernel developer at Freescale ___ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
Re: CONFIG_NO_HZ causing poor console responsiveness
On Thu, 2010-07-01 at 16:55 -0500, Timur Tabi wrote:
> On Tue, Jun 29, 2010 at 2:54 PM, Timur Tabi 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
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
Tested-by: Brian Bloniarz
Signed-off-by: Mike Galbraith
Signed-off-by: Peter Zijlstra
Cc: Jiri Kosina
Cc: Linus Torvalds
Cc: Greg KH
Cc: Alan Cox
Cc: OGAWA Hirofumi
Cc: Jef Driesen
LKML-Reference: <1276790557.27822.516.ca...@twins>
Signed-off-by: Thomas Gleixner
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 {
___
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Re: CONFIG_NO_HZ causing poor console responsiveness
On Jul 1, 2010, at 10:46 PM, "Mike Galbraith" wrote: > > Hi Timur, > > This has already fixed. Below is the final fix from tip. Than Mike. I thought I was using the latest code, but I guess not. ___ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
Re: CONFIG_NO_HZ causing poor console responsiveness
On Tue, 2010-06-29 at 14:54 -0500, Timur Tabi 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 don't have time to debug this thoroughly at the moment. The problem > occurs in the latest kernel, but it appears not to occur in 2.6.32. > > Has anyone else seen anything like this? I noticed that on the bimini with 2.6.35-rc* though I didn't get to track it down yet. Cheers, Ben. ___ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
RE: CONFIG_NO_HZ causing poor console responsiveness
>-Original Message- >From: linuxppc-dev-bounces+leoli=freescale@lists.ozlabs.org >[mailto:linuxppc-dev-bounces+leoli=freescale@lists.ozlabs.org] On >Behalf Of Benjamin Herrenschmidt >Sent: Friday, July 02, 2010 1:47 PM >To: Tabi Timur-B04825 >Cc: Linuxppc-dev Development >Subject: Re: CONFIG_NO_HZ causing poor console responsiveness > >On Tue, 2010-06-29 at 14:54 -0500, Timur Tabi 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 don't have time to debug this thoroughly at the moment. The problem >> occurs in the latest kernel, but it appears not to occur in 2.6.32. >> >> Has anyone else seen anything like this? > >I noticed that on the bimini with 2.6.35-rc* though I didn't get to track >it down yet. Patch found at the following location fixed this problem. http://www.spinics.net/lists/linux-tip-commits/msg08279.html Hope it has already been merged. - Leo ___ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
