On Sat, Jul 15, 2017 at 09:41:35AM -0700, Andrew Lutomirski wrote: > On Sat, Jul 15, 2017 at 8:55 AM, Mel Gorman <mgorman@xxxxxxx> wrote: > > The patch looks fine to be but when writing the patch, I wondered why the > > original code disabled preemption before inc_mm_tlb_gen. I didn't spot > > the reason for it but given the importance of properly synchronising with > > switch_mm, I played it safe. However, this should be ok on top and > > maintain the existing sequences > > LGTM. You could also fold it into your patch or even put it before > your patch, too. > Thanks. > FWIW, I didn't have any real reason to inc_mm_tlb_gen() with > preemption disabled. I think I did it because the code it replaced > was also called with preemption off. That being said, it's > effectively a single instruction, so it barely matters latency-wise. > (Hmm. Would there be a performance downside if a thread got preempted > between inc_mm_tlb_gen() and doing the flush? There isn't a preemption point until the point where irqs are disabled/enabled for the local TLB flush so it doesn't really matter. It can still be preempted by an interrupt but that's not surprising. I don't think it matters that much either way so I'll leave it at it is. -- Mel Gorman SUSE Labs -- 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>
