On Wed, 2 Jun 2010 09:02:40 +0800 Dave Young <hidave.darkstar@xxxxxxxxx> wrote: > ... > > > Another possibility might be to change lru_add_drain_all() to use IPI > > interrupts rather than schedule_on_each_cpu(). __That would greatly > > speed up lru_add_drain_all(). __I don't recall why we did it that way > > and I don't immediately see a reason not to. __A few things in core mm > > would need to be changed from spin_lock_irq() to spin_lock_irqsave(). > > > > But I do have vague memories that there was a reason for it. > > > > <It's a huge PITA locating the commit which initially added > > lru_add_drain_all()> > > > > <ten minutes later> > > > > : tree 05d7615894131a368fc4943f641b11acdd2ae694 > > : parent e236a166b2bc437769a9b8b5d19186a3761bde48 > > : author Nick Piggin <npiggin@xxxxxxx> Thu, 19 Jan 2006 09:42:27 -0800 > > : committer Linus Torvalds <torvalds@xxxxxxxxxxx> Thu, 19 Jan 2006 11:20:17 -0800 > > : > > : [PATCH] mm: migration page refcounting fix > > : > > : Migration code currently does not take a reference to target page > > : properly, so between unlocking the pte and trying to take a new > > : reference to the page with isolate_lru_page, anything could happen to > > : it. > > : > > : Fix this by holding the pte lock until we get a chance to elevate the > > : refcount. > > : > > : Other small cleanups while we're here. > > > > It didn't tell us. > > > > <looks in the linux-mm archives> > > > > Nope, no rationale is provided there either. > > Maybe this thread? > > http://lkml.org/lkml/2008/10/23/226 Close. There's some talk there of using smp_call_function() (actually on_each_cpu()) within lru_add_drain_all(), but nobody seems to have tried it. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>