Rusty Russell wrote: > On Fri, 2007-08-17 at 09:35 +0200, Laurent Vivier wrote: >> Rusty Russell wrote: >>> Hi Laurent, >> Hi Rusty, >> how are your puppies ? > > They're getting a little fat, actually. Too many features ... > >> - remove PATCH 3, and add in task_struct a "ktime vtime" where we accumulate >> guest time (by calling something like guest_enter() and guest_exit() from the >> virtualization engine), and when in account_system_time() we have cputime > >> vtime we substrate vtime from cputime and add vtime to user time and guest >> time. >> But doing like this we freeze in kernel/sched.c the link between system time, >> user time and guest time (i.e. system time = system time - vtime, user time = >> user time + vtime and guest time = guest time + vtime). > > Actually, I think we can set a per-cpu "in_guest" flag for the scheduler > code, which then knows to add the tick to the guest time. That seems > the simplest possible solution. > > lguest or kvm would set the flag before running the guest (which is done > with preempt disabled or using preemption hooks), and reset it > afterwards. > > Thoughts?
It was my first attempt (except I didn't have a per-cpu flag, but a per-task
flag), it's not visible but I love simplicity... ;-)
A KVM VCPU is stopped by preemption, so when we enter in scheduler we have
exited from VCPU and thus this flags is off (so we account 0 to the guest). What
I did then is "set the flag on when we enter in the VCPU, and
"account_system_time()" sets the flag off when it adds this timeslice to cpustat
(and compute correctly guest, user, system time). But I didn't like this idea
because all code executed after we entered in the VCPU is accounted to the guest
until we have an account_system_time() and I suppose we can have real system
time in this part. And I guess a VCPU can be less than 1 ms (unit of cputime) in
a timeslice.
So ? What's best ?
Laurent
--
------------- [EMAIL PROTECTED] --------------
"Software is hard" - Donald Knuth
signature.asc
Description: OpenPGP digital signature
------------------------------------------------------------------------- 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 [email protected] https://lists.sourceforge.net/lists/listinfo/kvm-devel
