Re: [PATCH v4 2/2] mm: make lru_add_drain_all() selective

[Tejun Heo]

Hello,

On Tue, Aug 13, 2013 at 12:35:12PM -0700, Andrew Morton wrote:
> I don't know how lots-of-kmallocs compares with alloc_percpu()
> performance-wise.

If this is actually performance sensitive, the logical thing to do
would be pre-allocating per-cpu buffers instead of depending on
dynamic allocation.  Do the invocations need to be stackable?

> That being said, the `cpumask_var_t mask' which was added to
> lru_add_drain_all() is unneeded - it's just a temporary storage which
> can be eliminated by creating a schedule_on_each_cpu_cond() or whatever
> which is passed a function pointer of type `bool (*call_needed)(int
> cpu, void *data)'.

I'd really like to avoid that.  Decision callbacks tend to get abused
quite often and it's rather sad to do that because cpumask cannot be
prepared and passed around.  Can't it just preallocate all necessary
resources?

Thanks.

-- 
tejun
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/