On Mon, 30 Jun 2014 19:02:45 -0700 Laura Abbott <lau...@codeaurora.org> wrote:
> On 6/30/2014 6:07 PM, Gioh Kim wrote: > > Hi,Laura. > > > > I have a question. > > > > Does the __evict_bh_lru() not need bh_lru_lock()? > > The get_cpu_var() has already preenpt_disable() and can prevent other > > thread. > > But get_cpu_var cannot prevent IRQ context such like page-fault. > > I think if a page-fault occured and a file is read in IRQ context it can > > change cpu-lru. > > > > Is my concern correct? > > > > > > __evict_bh_lru is called via on_each_cpu_cond which I believe will disable > irqs. > I based the code on the existing invalidate_bh_lru which did not take the > bh_lru_lock > either. It's possible I missed something though. I fear that running on_each_cpu() within try_to_free_buffers() is going to be horridly expensive in some cases. Maybe CMA can use invalidate_bh_lrus() to shoot down everything before trying the allocation attempt. That should increase the success rate greatly and doesn't burden page reclaim. The bh LRU isn't terribly important from a performance point of view, so emptying it occasionally won't hurt. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/