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Subject: Re: [PATCH] percpu/module resevation: change resevation size iff
 X86_VSMP is set
To:     linux-kernel@vger.kernel.org
Cc:     Shai Fultheim <shai@scalemp.com>, Oren Twaig <oren@scalemp.com>
References: <1548071251-1849-1-git-send-email-eial@scalemp.com>
From:   Eial Czerwacki <eial@scalemp.com>
Organization: ScaleMP
Message-ID: <902b2b1d-e6bd-bded-dc72-ea792f807d18@scalemp.com>
Date:   Wed, 30 Jan 2019 12:33:32 +0200
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Greetings,

On 1/21/19 1:47 PM, Eial Czerwacki wrote:
> as reported in bug #201339 (https://bugzilla.kernel.org/show_bug.cgi?id=201339)
> by enabling X86_VSMP, INTERNODE_CACHE_BYTES's definition differs from the default one
> causing the struct size to exceed the size ok 8KB.
> 
> in order to avoid such issue, increse PERCPU_MODULE_RESERVE to 64KB if CONFIG_X86_VSMP is set.
> 
> the value was caculated on linux 4.20.3, make allmodconfig all and the following oneliner:
> for f in `find -name *.ko`; do echo $f; readelf -S $f  |grep perc; done |grep data..percpu -B 1 |grep ko |while read r; do echo -n "$r: "; objdump --syms --section=.data..percpu $r|grep data |sort -n  |awk '{c++; d=strtonum("0x" $1) + strtonum("0x" $5); if (m < d) m = d;} END {printf("%d vars-> last addr 0x%x ( %d )\n", c, m, m)}' ; done |column -t |sort -k 8 -n | awk '{print $8}'| paste -sd+ | bc
> 
> Signed-off-by: Eial Czerwacki <eial@scalemp.com>
> Signed-off-by: Shai Fultheim <shai@scalemp.com>
> Signed-off-by: Oren Twaig <oren@scalemp.com>
> ---
>  include/linux/percpu.h | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/include/linux/percpu.h b/include/linux/percpu.h
> index 70b7123..6b79693 100644
> --- a/include/linux/percpu.h
> +++ b/include/linux/percpu.h
> @@ -14,7 +14,11 @@
>  
>  /* enough to cover all DEFINE_PER_CPUs in modules */
>  #ifdef CONFIG_MODULES
> +#ifdef X86_VSMP
> +#define PERCPU_MODULE_RESERVE		(1 << 16)
> +#else
>  #define PERCPU_MODULE_RESERVE		(8 << 10)
> +#endif
>  #else
>  #define PERCPU_MODULE_RESERVE		0
>  #endif
> 
is it possible to push this patch to mainline?
it seems like no objections/comment regarding it exists.
we'd like to fix the bug mentioned above.