From d72915c60bff51495529449750e051d01b03c62f Mon Sep 17 00:00:00 2001 From: Stefan Hajnoczi Date: Wed, 1 Mar 2017 11:50:26 +0000 Subject: throttle: make throttle_config(throttle_get_config()) symmetric Throttling has a weird property that throttle_get_config() does not always return the same throttling settings that were given with throttle_config(). In other words, the set and get functions aren't symmetric. If .max is 0 then the throttling code assigns a default value of .avg / 10 in throttle_config(). This is an implementation detail of the throttling algorithm. When throttle_get_config() is called the .max value returned should still be 0. Users are exposed to this quirk via "info block" or "query-block" monitor commands. This has caused confusion because it looks like a bug when an unexpected value is reported. This patch hides the .max value adjustment in throttle_get_config() and updates test-throttle.c appropriately. Reported-by: Nini Gu Signed-off-by: Stefan Hajnoczi Reviewed-by: Alberto Garcia Message-id: 20170301115026.22621-4-stefanha@redhat.com Signed-off-by: Stefan Hajnoczi --- util/throttle.c | 14 ++++++++++++++ 1 file changed, 14 insertions(+) (limited to 'util/throttle.c') diff --git a/util/throttle.c b/util/throttle.c index 3817d9b904..3570ed25fc 100644 --- a/util/throttle.c +++ b/util/throttle.c @@ -380,6 +380,14 @@ static void throttle_fix_bucket(LeakyBucket *bkt) } } +/* undo internal bucket parameter changes (see throttle_fix_bucket()) */ +static void throttle_unfix_bucket(LeakyBucket *bkt) +{ + if (bkt->max < bkt->avg) { + bkt->max = 0; + } +} + /* take care of canceling a timer */ static void throttle_cancel_timer(QEMUTimer *timer) { @@ -420,7 +428,13 @@ void throttle_config(ThrottleState *ts, */ void throttle_get_config(ThrottleState *ts, ThrottleConfig *cfg) { + int i; + *cfg = ts->cfg; + + for (i = 0; i < BUCKETS_COUNT; i++) { + throttle_unfix_bucket(&cfg->buckets[i]); + } } -- cgit 1.4.1