| Message ID | 147145440828.25877.10082549766938645168.stgit@Solace.fritz.box (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 17/08/16 18:20, Dario Faggioli wrote: > Credit2 is already event based, rather than tick > based. This means, the time at which the (i+1)-eth > scheduling decision needs to happen is computed > during the i-eth scheduling decision, and a timer > is set accordingly. > > If there's nothing imminent (or, the most imminent > event is really really really far away), it is > ok to say "well, let's double-check things in > a little bit anyway", but such 'little bit' does > not need to be too little, as, most likely, it's > just pure overhead. > > The current period, for this "safety catch"-alike > timer is 2ms, which indeed is high, but it can > well be higher. In fact, benchmarks show that > setting it to 10ms --combined with other > optimizations-- does actually improve performance. > > Signed-off-by: Dario Faggioli <dario.faggioli@citrix.com> We might as well toss this one in: Reviewed-by: George Dunlap <george.dunlap@citrix.com>
diff --git a/xen/common/sched_credit2.c b/xen/common/sched_credit2.c index 21b1f91..6963872 100644 --- a/xen/common/sched_credit2.c +++ b/xen/common/sched_credit2.c @@ -152,7 +152,7 @@ /* Reset: Value below which credit will be reset. */ #define CSCHED2_CREDIT_RESET 0 /* Max timer: Maximum time a guest can be run for. */ -#define CSCHED2_MAX_TIMER MILLISECS(2) +#define CSCHED2_MAX_TIMER CSCHED2_CREDIT_INIT #define CSCHED2_IDLE_CREDIT (-(1<<30))
Credit2 is already event based, rather than tick based. This means, the time at which the (i+1)-eth scheduling decision needs to happen is computed during the i-eth scheduling decision, and a timer is set accordingly. If there's nothing imminent (or, the most imminent event is really really really far away), it is ok to say "well, let's double-check things in a little bit anyway", but such 'little bit' does not need to be too little, as, most likely, it's just pure overhead. The current period, for this "safety catch"-alike timer is 2ms, which indeed is high, but it can well be higher. In fact, benchmarks show that setting it to 10ms --combined with other optimizations-- does actually improve performance. Signed-off-by: Dario Faggioli <dario.faggioli@citrix.com> --- Cc: George Dunlap <george.dunlap@citrix.com> Cc: Anshul Makkar <anshul.makkar@citrix.com> --- xen/common/sched_credit2.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)