On Mon, 2014-07-21 at 14:31 -0700, Andy Lutomirski wrote: > On Mon, Jul 21, 2014 at 2:27 PM, Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote: > > All this is predicated on the fact that syscalls are 'expensive'. > > Weren't syscalls only 100s of cycles? All this bitmap mucking is far > > more expensive due to cacheline misses, which due to the size of the > > things is almost guaranteed. > > 120 - 300 cycles for me, unless tracing happens, and I'm working on > reducing the incidence of tracing. fwiw here's what lmbench's lat_ctx says on my system . For 'accuracy', I kept the runs short. http://www.stgolabs.net/lat_ctx.png -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
