On Tue, 2013-04-30 at 18:27 +0000, Christoph Lameter wrote: > On Tue, 30 Apr 2013, Tim Chen wrote: > > > > But you will have to dereference the pointer whenever you want the batch > > > size from the hot path. Looks like it would be better to put the value > > > there directly. You have a list of percpu counters that can be traversed > > > to change the batch size. > > > > > > > I have considered that. But the list is not available unless we have > > CONFIG_HOTPLUG_CPU compiled in. > > percpu counters are performance sensitive and with the pointer you > will need to reference another one increasing the cache footprint. You are > touching an additional cacheline somewhere in memory frequently. Not good. > Seems like there's objection to make batch a pointer and I'll have to store its value in per cpu pointer. Will it be acceptable if I make the per cpu counter list under CONFIG_CPU_HOTPLUG default? I will need the list to go through all counters to update the batch value sizes. The alternative will be to make the configurable batch option only available under CONFIG_HOTPLUG_CPU. Which is the preferable approach or there are other clever alternatives? Tim -- 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>