On Thu, 08/16 00:29, Emilio G. Cota wrote: > On Wed, Aug 15, 2018 at 19:55:14 -0400, Emilio G. Cota wrote: > > On Wed, Aug 15, 2018 at 00:53:23 -0400, Emilio G. Cota wrote: > > > On Wed, Aug 15, 2018 at 11:09:42 +0800, Fam Zheng wrote: > > > > On Mon, 08/13 13:11, Emilio G. Cota wrote: > > > > > + --enable-sync-profiler) sync_profiler="yes" > > > > > + ;; > > > > > > > > Curious, not asking for a change: can this be made a runtime option > > > > instead of > > > > compile time, since there's no library dependencies? That should make > > > > this > > > > somewhat easier to use. > > > > > > Good point. I'll do some profiling tomorrow to see how the latency > > > of the locking primitives could be minimized (ideally, not using > > > the profiler should just add a well-predicted branch). > > > > I reduced it to just a branch, but still, I measured a few percentage > > points (1-2%, depending on the machine) slowdown when this is a > > run-time option. (This is for a bootup+shutdown test of a guest.) > > > > So I'll keep it as a build-time option, then. > > I looked further into this. Turns out we don't need the branch at all; > we can make indirect calls via function pointers, where the > pointers are set by qsp_enable/disable(). > > Overhead of doing things this way is within noise range, since > compilers and CPUs are so good at dealing with indirect calls.
Very nice finding! Thanks. Fam > > I'll send a v2 tomorrow. > > Emilio
