From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:48745) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cifop-0007l2-2e for qemu-devel@nongnu.org; Tue, 28 Feb 2017 06:19:48 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1cifoo-0006IS-23 for qemu-devel@nongnu.org; Tue, 28 Feb 2017 06:19:47 -0500 From: Stefan Hajnoczi Date: Tue, 28 Feb 2017 11:19:35 +0000 Message-Id: <20170228111935.10826-3-stefanha@redhat.com> In-Reply-To: <20170228111935.10826-1-stefanha@redhat.com> References: <20170228111935.10826-1-stefanha@redhat.com> Subject: [Qemu-devel] [PATCH v2 2/2] throttle: make throttle_config(throttle_get_config()) symmetric List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: Nini Gu , qemu-block@nongnu.org, Alberto Garcia , Stefan Hajnoczi 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 --- tests/test-throttle.c | 8 ++++---- util/throttle.c | 16 ++++++++++++++++ 2 files changed, 20 insertions(+), 4 deletions(-) diff --git a/tests/test-throttle.c b/tests/test-throttle.c index 363b59a..3d6bb82 100644 --- a/tests/test-throttle.c +++ b/tests/test-throttle.c @@ -205,8 +205,8 @@ static void test_config_functions(void) orig_cfg.buckets[THROTTLE_OPS_READ].avg = 69; orig_cfg.buckets[THROTTLE_OPS_WRITE].avg = 23; - orig_cfg.buckets[THROTTLE_BPS_TOTAL].max = 0; /* should be corrected */ - orig_cfg.buckets[THROTTLE_BPS_READ].max = 1; /* should not be corrected */ + orig_cfg.buckets[THROTTLE_BPS_TOTAL].max = 0; + orig_cfg.buckets[THROTTLE_BPS_READ].max = 1; orig_cfg.buckets[THROTTLE_BPS_WRITE].max = 120; orig_cfg.buckets[THROTTLE_OPS_TOTAL].max = 150; @@ -246,8 +246,8 @@ static void test_config_functions(void) g_assert(final_cfg.buckets[THROTTLE_OPS_READ].avg == 69); g_assert(final_cfg.buckets[THROTTLE_OPS_WRITE].avg == 23); - g_assert(final_cfg.buckets[THROTTLE_BPS_TOTAL].max == 15.3);/* fixed */ - g_assert(final_cfg.buckets[THROTTLE_BPS_READ].max == 1); /* not fixed */ + g_assert(final_cfg.buckets[THROTTLE_BPS_TOTAL].max == 0); + g_assert(final_cfg.buckets[THROTTLE_BPS_READ].max == 1); g_assert(final_cfg.buckets[THROTTLE_BPS_WRITE].max == 120); g_assert(final_cfg.buckets[THROTTLE_OPS_TOTAL].max == 150); diff --git a/util/throttle.c b/util/throttle.c index 3817d9b..d87b421 100644 --- a/util/throttle.c +++ b/util/throttle.c @@ -380,6 +380,16 @@ static void throttle_fix_bucket(LeakyBucket *bkt) } } +/* undo internal bucket parameter changes (see throttle_fix_bucket()) */ +static void throttle_unfix_bucket(LeakyBucket *bkt) +{ + double min = bkt->avg / 10; + + if (bkt->max == min) { + bkt->max = 0; + } +} + /* take care of canceling a timer */ static void throttle_cancel_timer(QEMUTimer *timer) { @@ -420,7 +430,13 @@ 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]); + } } -- 2.9.3