On Thu, Apr 14, 2016 at 04:44:48PM +0200, Roman Peniaev wrote: > On Thu, Apr 14, 2016 at 3:49 PM, Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> wrote: > > On Thu, Apr 14, 2016 at 03:13:26PM +0200, Roman Peniaev wrote: > >> Hi, Chris. > >> > >> Is it made on purpose not to drop VM_LAZY_FREE flag in > >> __purge_vmap_area_lazy()? With your patch va->flags > >> will have two bits set: VM_LAZY_FREE | VM_LAZY_FREEING. > >> Seems it is not that bad, because all other code paths > >> do not care, but still the change is not clear. > > > > Oh, that was just a bad deletion. > > > >> Also, did you consider to avoid taking static purge_lock > >> in __purge_vmap_area_lazy() ? Because, with your change > >> it seems that you can avoid taking this lock at all. > >> Just be careful when you observe llist as empty, i.e. > >> nr == 0. > > > > I admit I only briefly looked at the lock. I will be honest and say I > > do not fully understand the requirements of the sync/force_flush > > parameters. > > if sync: > o I can wait for other purge in progress > (do not care if purge_lock is dropped) > > o purge fragmented blocks > > if force_flush: > o even nothing to purge, flush TLB, which is costly. > (again sync-like is implied) > > > purge_fragmented_blocks() manages per-cpu lists, so that looks safe > > under its own rcu_read_lock. > > > > Yes, it looks feasible to remove the purge_lock if we can relax sync. > > what is still left is waiting on vmap_area_lock for !sync mode. > but probably is not that bad. Ok, that's bit beyond my comfort zone with a patch to change the free list handling. I'll chicken out for the time being, atm I am more concerned that i915.ko may call set_page_wb() frequently on individual pages. -Chris -- Chris Wilson, Intel Open Source Technology Centre -- 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>