* /proc/profile broken on UP machines in 2.6.29-rc3
@ 2009-02-09 14:50 Lennert Buytenhek
2009-02-09 19:20 ` Hugh Dickins
0 siblings, 1 reply; 3+ messages in thread
From: Lennert Buytenhek @ 2009-02-09 14:50 UTC (permalink / raw)
To: rusty; +Cc: linux-kernel
I'm about 130k emails behind on my linux-kernel@ subscription, so I'm
not entirely sure whether this has been reported, but it seems that
profiling is broken on !CONFIG_SMP builds in 2.6.29-rc3.
It appears that since this commit:
commit c309b917cab55799ea489d7b5f1b77025d9f8462
Author: Rusty Russell <rusty@rustcorp.com.au>
Date: Thu Jan 1 10:12:27 2009 +1030
cpumask: convert kernel/profile.c
there's no longer anything that sets any bits in prof_cpu_mask on
UP systems at all (the default was to assign CPU_MASK_ALL, and
profile_cpu_callback() which clears/sets bits at run time is only
built and registered on SMP builds), so the cpumask_test_cpu()
test in profile_tick() always fails, and no samples are ever counted.
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: /proc/profile broken on UP machines in 2.6.29-rc3
2009-02-09 14:50 /proc/profile broken on UP machines in 2.6.29-rc3 Lennert Buytenhek
@ 2009-02-09 19:20 ` Hugh Dickins
2009-02-09 23:50 ` Ingo Molnar
0 siblings, 1 reply; 3+ messages in thread
From: Hugh Dickins @ 2009-02-09 19:20 UTC (permalink / raw)
To: Lennert Buytenhek; +Cc: Rusty Russell, Rafael Wysocki, linux-kernel
On Mon, 9 Feb 2009, Lennert Buytenhek wrote:
> I'm about 130k emails behind on my linux-kernel@ subscription, so I'm
> not entirely sure whether this has been reported, but it seems that
> profiling is broken on !CONFIG_SMP builds in 2.6.29-rc3.
Yes, and CONFIG_SMP builds, and 2.6.29-rc4.
> It appears that since this commit:
>
> commit c309b917cab55799ea489d7b5f1b77025d9f8462
> Author: Rusty Russell <rusty@rustcorp.com.au>
> Date: Thu Jan 1 10:12:27 2009 +1030
>
> cpumask: convert kernel/profile.c
>
> there's no longer anything that sets any bits in prof_cpu_mask on
> UP systems at all (the default was to assign CPU_MASK_ALL, and
> profile_cpu_callback() which clears/sets bits at run time is only
> built and registered on SMP builds), so the cpumask_test_cpu()
> test in profile_tick() always fails, and no samples are ever counted.
I guess if you cpu down and up, or suspend and resume, that will get
aux cpus profiling in the SMP case, but basically SMP is as broken as
UP. I noticed yesterday, took a look earlier today, here's the patch
which gets it working for me:
[PATCH] fix broken profiling regression
Commit c309b917cab55799ea489d7b5f1b77025d9f8462 "cpumask: convert
kernel/profile.c" broke profiling. prof_cpu_mask was previously
initialized to CPU_MASK_ALL, but left uninitialized in that commit.
We need to copy cpu_possible_mask (cpu_online_mask is not enough).
Signed-off-by: Hugh Dickins <hugh@veritas.com>
---
kernel/profile.c | 3 +++
1 file changed, 3 insertions(+)
--- 2.6.29-rc4/kernel/profile.c 2009-01-11 01:33:38.000000000 +0000
+++ linux/kernel/profile.c 2009-02-09 15:23:34.000000000 +0000
@@ -114,12 +114,15 @@ int __ref profile_init(void)
if (!slab_is_available()) {
prof_buffer = alloc_bootmem(buffer_bytes);
alloc_bootmem_cpumask_var(&prof_cpu_mask);
+ cpumask_copy(prof_cpu_mask, cpu_possible_mask);
return 0;
}
if (!alloc_cpumask_var(&prof_cpu_mask, GFP_KERNEL))
return -ENOMEM;
+ cpumask_copy(prof_cpu_mask, cpu_possible_mask);
+
prof_buffer = kzalloc(buffer_bytes, GFP_KERNEL);
if (prof_buffer)
return 0;
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: /proc/profile broken on UP machines in 2.6.29-rc3
2009-02-09 19:20 ` Hugh Dickins
@ 2009-02-09 23:50 ` Ingo Molnar
0 siblings, 0 replies; 3+ messages in thread
From: Ingo Molnar @ 2009-02-09 23:50 UTC (permalink / raw)
To: Hugh Dickins
Cc: Lennert Buytenhek, Rusty Russell, Rafael Wysocki, linux-kernel
* Hugh Dickins <hugh@veritas.com> wrote:
> On Mon, 9 Feb 2009, Lennert Buytenhek wrote:
>
> > I'm about 130k emails behind on my linux-kernel@ subscription, so I'm
> > not entirely sure whether this has been reported, but it seems that
> > profiling is broken on !CONFIG_SMP builds in 2.6.29-rc3.
>
> Yes, and CONFIG_SMP builds, and 2.6.29-rc4.
>
> > It appears that since this commit:
> >
> > commit c309b917cab55799ea489d7b5f1b77025d9f8462
> > Author: Rusty Russell <rusty@rustcorp.com.au>
> > Date: Thu Jan 1 10:12:27 2009 +1030
> >
> > cpumask: convert kernel/profile.c
> >
> > there's no longer anything that sets any bits in prof_cpu_mask on
> > UP systems at all (the default was to assign CPU_MASK_ALL, and
> > profile_cpu_callback() which clears/sets bits at run time is only
> > built and registered on SMP builds), so the cpumask_test_cpu()
> > test in profile_tick() always fails, and no samples are ever counted.
>
> I guess if you cpu down and up, or suspend and resume, that will get
> aux cpus profiling in the SMP case, but basically SMP is as broken as
> UP. I noticed yesterday, took a look earlier today, here's the patch
> which gets it working for me:
>
>
> [PATCH] fix broken profiling regression
>
> Commit c309b917cab55799ea489d7b5f1b77025d9f8462 "cpumask: convert
> kernel/profile.c" broke profiling. prof_cpu_mask was previously
> initialized to CPU_MASK_ALL, but left uninitialized in that commit.
> We need to copy cpu_possible_mask (cpu_online_mask is not enough).
>
> Signed-off-by: Hugh Dickins <hugh@veritas.com>
> ---
>
> kernel/profile.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> --- 2.6.29-rc4/kernel/profile.c 2009-01-11 01:33:38.000000000 +0000
> +++ linux/kernel/profile.c 2009-02-09 15:23:34.000000000 +0000
> @@ -114,12 +114,15 @@ int __ref profile_init(void)
> if (!slab_is_available()) {
> prof_buffer = alloc_bootmem(buffer_bytes);
> alloc_bootmem_cpumask_var(&prof_cpu_mask);
> + cpumask_copy(prof_cpu_mask, cpu_possible_mask);
> return 0;
> }
>
> if (!alloc_cpumask_var(&prof_cpu_mask, GFP_KERNEL))
> return -ENOMEM;
>
> + cpumask_copy(prof_cpu_mask, cpu_possible_mask);
> +
> prof_buffer = kzalloc(buffer_bytes, GFP_KERNEL);
> if (prof_buffer)
> return 0;
indeed. Applied to tip/tracing/urgent, thanks Hugh!
Ingo
^ permalink raw reply [flat|nested] 3+ messages in thread
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2009-02-09 14:50 /proc/profile broken on UP machines in 2.6.29-rc3 Lennert Buytenhek
2009-02-09 19:20 ` Hugh Dickins
2009-02-09 23:50 ` Ingo Molnar
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