linux-kernel - Re: [PATCH v6 00/37] Memory allocation profiling

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Date: Fri, 5 Apr 2024 08:20:44 -0700
From: Suren Baghdasaryan <surenb@...gle.com>
To: Klara Modin <klarasmodin@...il.com>
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Subject: Re: [PATCH v6 00/37] Memory allocation profiling

On Fri, Apr 5, 2024 at 7:30 AM Klara Modin <klarasmodin@...il.com> wrote:
>
> On 2024-04-05 16:14, Suren Baghdasaryan wrote:
> > On Fri, Apr 5, 2024 at 6:37 AM Klara Modin <klarasmodin@...il.com> wrote:
> >> If I enable this, I consistently get percpu allocation failures. I can
> >> occasionally reproduce it in qemu. I've attached the logs and my config,
> >> please let me know if there's anything else that could be relevant.
> >
> > Thanks for the report!
> > In debug_alloc_profiling.log I see:
> >
> > [    7.445127] percpu: limit reached, disable warning
> >
> > That's probably the reason. I'll take a closer look at the cause of
> > that and how we can fix it.
>
> Thanks!

In the build that produced debug_alloc_profiling.log I think we are
consuming all the per-cpu memory reserved for the modules. Could you
please try this change and see if that fixes the issue:

 include/linux/percpu.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/percpu.h b/include/linux/percpu.h
index a790afba9386..03053de557cf 100644
--- a/include/linux/percpu.h
+++ b/include/linux/percpu.h
@@ -17,7 +17,7 @@
 /* enough to cover all DEFINE_PER_CPUs in modules */
 #ifdef CONFIG_MODULES
 #ifdef CONFIG_MEM_ALLOC_PROFILING
-#define PERCPU_MODULE_RESERVE (8 << 12)
+#define PERCPU_MODULE_RESERVE (8 << 13)
 #else
 #define PERCPU_MODULE_RESERVE (8 << 10)
 #endif

>
> >
> >   In qemu-alloc3.log I see couple of warnings:
> >
> > [    1.111620] alloc_tag was not set
> > [    1.111880] WARNING: CPU: 0 PID: 164 at
> > include/linux/alloc_tag.h:118 kfree (./include/linux/alloc_tag.h:118
> > (discriminator 1) ./include/linux/alloc_tag.h:161 (discriminator 1)
> > mm/slub.c:2043 ...
> >
> > [    1.161710] alloc_tag was not cleared (got tag for fs/squashfs/cachec:413)
> > [    1.162289] WARNING: CPU: 0 PID: 195 at
> > include/linux/alloc_tag.h:109 kmalloc_trace_noprof
> > (./include/linux/alloc_tag.h:109 (discriminator 1)
> > ./include/linux/alloc_tag.h:149 (discriminator 1) ...
> >
> > Which means we missed to instrument some allocation. Can you please
> > check if disabling CONFIG_MEM_ALLOC_PROFILING_DEBUG fixes QEMU case?
> > In the meantime I'll try to reproduce and fix this.
> > Thanks,
> > Suren.
>
> That does seem to be the case from what I can tell. I didn't get the
> warning in qemu consistently, but it hasn't reappeared for a number of
> times at least with the debugging option off.
>
> Regards,
> Klara Modin