On Fri, Mar 27, 2015 at 3:00 PM, Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote: > On Fri, Mar 27, 2015 at 10:16:13AM +0100, Peter Zijlstra wrote: >> So the issue seems to be that we need base->running_timer in order to >> tell if a callback is running, right? >> >> We could align the base on 8 bytes to gain an extra bit in the pointer >> and use that bit to indicate the running state. Then these sites can >> spin on that bit while we can change the actual base pointer. > > Even though tvec_base has ____cacheline_aligned stuck on, most are > allocated using kzalloc_node() which does not actually respect that but > already guarantees a minimum u64 alignment, so I think we can use that > third bit without too much magic. Right. So what I tried earlier was very much similar to you are suggesting. The only difference was that I haven't made much attempts towards saving memory. But Thomas didn't like it for sure and I believe that Rant will hold true for what you are suggesting as well, isn't it ? http://lists.linaro.org/pipermail/linaro-kernel/2013-November/008866.html -- 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>