From cf0c29d1a99f17fe9e501e4e09d9d1e3eced6f98 Mon Sep 17 00:00:00 2001 From: Jan Beulich Date: Thu, 28 Feb 2013 11:06:42 +0100 Subject: [PATCH] credit1: track residual from divisions done during accounting This should help with under-accounting of vCPU-s running for extremly short periods of time, but becoming runnable again at a high frequency. Signed-off-by: Jan Beulich Acked-by: George Dunlap --- xen/common/sched_credit.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/xen/common/sched_credit.c b/xen/common/sched_credit.c index df2d0765cd..7fbc0059ad 100644 --- a/xen/common/sched_credit.c +++ b/xen/common/sched_credit.c @@ -19,6 +19,7 @@ #include #include #include +#include #include #include #include @@ -136,6 +137,7 @@ struct csched_vcpu { struct csched_dom *sdom; struct vcpu *vcpu; atomic_t credit; + unsigned int residual; s_time_t start_time; /* When we were scheduled (used for credit) */ uint16_t flags; int16_t pri; @@ -242,6 +244,7 @@ __runq_remove(struct csched_vcpu *svc) static void burn_credits(struct csched_vcpu *svc, s_time_t now) { s_time_t delta; + uint64_t val; unsigned int credits; /* Assert svc is current */ @@ -250,7 +253,10 @@ static void burn_credits(struct csched_vcpu *svc, s_time_t now) if ( (delta = now - svc->start_time) <= 0 ) return; - credits = (delta*CSCHED_CREDITS_PER_MSEC + MILLISECS(1)/2) / MILLISECS(1); + val = delta * CSCHED_CREDITS_PER_MSEC + svc->residual; + svc->residual = do_div(val, MILLISECS(1)); + credits = val; + ASSERT(credits == val); /* make sure we haven't truncated val */ atomic_sub(credits, &svc->credit); svc->start_time += (credits * MILLISECS(1)) / CSCHED_CREDITS_PER_MSEC; } -- 2.39.5