On Mon, 30 Jun 2014 19:02:45 -0700 Laura Abbott <lauraa@xxxxxxxxxxxxxx> 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, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>