On Tue, 21 Aug 2007, Luca Tettamanti wrote: > Avi Kivity ha scritto: >> Luca Tettamanti wrote: >>> At 1000Hz: >>> >>> QEMU >>> hpet 5.5% >>> dynticks 11.7% >>> >>> KVM >>> hpet 3.4% >>> dynticks 7.3% >>> >>> No surprises here, you can see the additional 1k syscalls per second. >> >> This is very surprising to me. The 6.2% difference for the qemu case >> translates to 62ms per second, or 62us per tick at 1000Hz. That's more >> than a hundred simple syscalls on modern processors. We shouldn't have to >> issue a hundred syscalls per guest clock tick. > [..snip preulde..]
> I've also tried APC which was suggested by malc[1] and: > - readings are far more stable > - the gap between dynticks and non-dynticks seems not significant [..dont snip the obvious fact and snip the numbers..] > > Luca > [1] copy_to_user inside spinlock is a big no-no ;) > [..notice a projectile targeting at you and rush to see the code..] Mixed feelings about this... But in principle the code ofcourse is dangerous, thank you kindly for pointing this out. I see two ways out of this: a. moving the lock/unlock inside the loop with unlock preceding sometimes sleep deprived copy_to_user b. fill temporaries and after the loop is done copy it in one go Too late, too hot, i wouldn't mind beying on a receiving side of a good advice. -- vale ------------------------------------------------------------------------- This SF.net email is sponsored by: Splunk Inc. Still grepping through log files to find problems? Stop. Now Search log events and configuration files using AJAX and a browser. Download your FREE copy of Splunk now >> http://get.splunk.com/ _______________________________________________ kvm-devel mailing list kvm-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/kvm-devel