On Fri, Oct 28, 2011 at 6:06 AM, Christoph Lameter <cl@xxxxxxxxxx> wrote:
> On Sun, 23 Oct 2011, Gilad Ben-Yossef wrote:
>
>> diff --git a/include/linux/slub_def.h b/include/linux/slub_def.h
>> index f58d641..b130f61 100644
>> --- a/include/linux/slub_def.h
>> +++ b/include/linux/slub_def.h
>> @@ -102,6 +102,9 @@ struct kmem_cache {
>> */
>> int remote_node_defrag_ratio;
>> #endif
>> +
>> + /* Which CPUs hold local slabs for this cache. */
>> + cpumask_var_t cpus_with_slabs;
>> struct kmem_cache_node *node[MAX_NUMNODES];
>> };
>
> Please do not add fields to structures for passing parameters to
> functions. This just increases the complexity of the patch and extends a
> structures needlessly.
The field was added to provide storage to cpus_with_slabs during
flush_all, since otherwise cpus_with_slabs, being a cpumask, would
require a kmem_cache allocation in the middle of flush_all for
CONFIG_CPUMASK_OFF_STACK=y case, which Pekka E. objected to.
The next patch in the series makes the field (and overhead) only added
for CONFIG_CPUMASK_OFF_STACK=y case but I wanted to break out the
addition to the patch core feature and the optimization of only adding
the field for CONFIG_CPUMASK_OFF_STACK=y, so this patch as is without
the next one is only good for bisect value.
I should have probably have commented about it in the description of
this patch and not only in the next one. Sorry about that. I will fix
it for the next round.
>
>> diff --git a/mm/slub.c b/mm/slub.c
>> index 7c54fe8..f8cbf2d 100644
>> --- a/mm/slub.c
>> +++ b/mm/slub.c
>> @@ -1948,7 +1948,18 @@ static void flush_cpu_slab(void *d)
>>
>> static void flush_all(struct kmem_cache *s)
>> {
>> - on_each_cpu(flush_cpu_slab, s, 1);
>> + struct kmem_cache_cpu *c;
>> + int cpu;
>> +
>> + for_each_online_cpu(cpu) {
>> + c = per_cpu_ptr(s->cpu_slab, cpu);
>> + if (c && c->page)
>> + cpumask_set_cpu(cpu, s->cpus_with_slabs);
>> + else
>> + cpumask_clear_cpu(cpu, s->cpus_with_slabs);
>> + }
>> +
>> + on_each_cpu_mask(s->cpus_with_slabs, flush_cpu_slab, s, 1);
>> }
>
>
> You do not need s->cpus_with_slabs to be in kmem_cache. Make it a local
> variable instead.
That is what the next patch does - for CONFIG_CPUMASK_OFFSTACK=n, alt least.
Thanks,
Gilad
--
Gilad Ben-Yossef
Chief Coffee Drinker
gilad@xxxxxxxxxxxxx
Israel Cell: +972-52-8260388
US Cell: +1-973-8260388
http://benyossef.com
"I've seen things you people wouldn't believe. Goto statements used to
implement co-routines. I watched C structures being stored in
registers. All those moments will be lost in time... like tears in
rain... Time to die. "
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