diff mbox

[v2,5/7] throttle: Make LeakyBucket.avg and LeakyBucket.max integer types

Message ID f29b840422767b5be2c41c2dfdbbbf6c5f8fedf8.1503580370.git.berto@igalia.com
State New
Headers show

Commit Message

Alberto Garcia Aug. 24, 2017, 1:24 p.m. UTC 
Both the throttling limits set with the throttling.iops-* and
throttling.bps-* options and their QMP equivalents defined in the
BlockIOThrottle struct are integer values.

Those limits are also reported in the BlockDeviceInfo struct and they
are integers there as well.

Therefore there's no reason to store them internally as double and do
the conversion everytime we're setting or querying them, so this patch
uses uint64_t for those types. Let's also use an unsigned type because
we don't allow negative values anyway.

LeakyBucket.level and LeakyBucket.burst_level do however remain double
because their value changes depending on the fraction of time elapsed
since the previous I/O operation.

Signed-off-by: Alberto Garcia <berto@igalia.com>
---
 include/qemu/throttle.h | 4 ++--
 tests/test-throttle.c   | 3 ++-
 util/throttle.c         | 7 +++----
 3 files changed, 7 insertions(+), 7 deletions(-)

Comments

Eric Blake Aug. 29, 2017, 9:29 p.m. UTC | #1 
On 08/24/2017 08:24 AM, Alberto Garcia wrote:
> Both the throttling limits set with the throttling.iops-* and
> throttling.bps-* options and their QMP equivalents defined in the
> BlockIOThrottle struct are integer values.
> 
> Those limits are also reported in the BlockDeviceInfo struct and they
> are integers there as well.
> 
> Therefore there's no reason to store them internally as double and do
> the conversion everytime we're setting or querying them, so this patch
> uses uint64_t for those types. Let's also use an unsigned type because
> we don't allow negative values anyway.
> 
> LeakyBucket.level and LeakyBucket.burst_level do however remain double
> because their value changes depending on the fraction of time elapsed
> since the previous I/O operation.
> 
> Signed-off-by: Alberto Garcia <berto@igalia.com>
> ---
>  include/qemu/throttle.h | 4 ++--
>  tests/test-throttle.c   | 3 ++-
>  util/throttle.c         | 7 +++----
>  3 files changed, 7 insertions(+), 7 deletions(-)
> 

Reviewed-by: Eric Blake <eblake@redhat.com>
diff mbox

Patch

diff --git a/include/qemu/throttle.h b/include/qemu/throttle.h
index 66a8ac10a4..6e31155fd4 100644
--- a/include/qemu/throttle.h
+++ b/include/qemu/throttle.h
@@ -77,8 +77,8 @@  typedef enum {
  */
 
 typedef struct LeakyBucket {
-    double  avg;              /* average goal in units per second */
-    double  max;              /* leaky bucket max burst in units */
+    uint64_t avg;             /* average goal in units per second */
+    uint64_t max;             /* leaky bucket max burst in units */
     double  level;            /* bucket level in units */
     double  burst_level;      /* bucket level in units (for computing bursts) */
     unsigned burst_length;    /* max length of the burst period, in seconds */
diff --git a/tests/test-throttle.c b/tests/test-throttle.c
index 768f11dfed..41c0dd2529 100644
--- a/tests/test-throttle.c
+++ b/tests/test-throttle.c
@@ -284,13 +284,14 @@  static void test_enabled(void)
     for (i = 0; i < BUCKETS_COUNT; i++) {
         throttle_config_init(&cfg);
         set_cfg_value(false, i, 150);
+        g_assert(throttle_is_valid(&cfg, NULL));
         g_assert(throttle_enabled(&cfg));
     }
 
     for (i = 0; i < BUCKETS_COUNT; i++) {
         throttle_config_init(&cfg);
         set_cfg_value(false, i, -150);
-        g_assert(!throttle_enabled(&cfg));
+        g_assert(!throttle_is_valid(&cfg, NULL));
     }
 }
 
diff --git a/util/throttle.c b/util/throttle.c
index 4e80a7ea54..80660ffd2c 100644
--- a/util/throttle.c
+++ b/util/throttle.c
@@ -106,13 +106,13 @@  int64_t throttle_compute_wait(LeakyBucket *bkt)
         /* If bkt->max is 0 we still want to allow short bursts of I/O
          * from the guest, otherwise every other request will be throttled
          * and performance will suffer considerably. */
-        bucket_size = bkt->avg / 10;
+        bucket_size = (double) bkt->avg / 10;
         burst_bucket_size = 0;
     } else {
         /* If we have a burst limit then we have to wait until all I/O
          * at burst rate has finished before throttling to bkt->avg */
         bucket_size = bkt->max * bkt->burst_length;
-        burst_bucket_size = bkt->max / 10;
+        burst_bucket_size = (double) bkt->max / 10;
     }
 
     /* If the main bucket is full then we have to wait */
@@ -338,8 +338,7 @@  bool throttle_is_valid(ThrottleConfig *cfg, Error **errp)
 
     for (i = 0; i < BUCKETS_COUNT; i++) {
         LeakyBucket *bkt = &cfg->buckets[i];
-        if (bkt->avg < 0 || bkt->max < 0 ||
-            bkt->avg > THROTTLE_VALUE_MAX || bkt->max > THROTTLE_VALUE_MAX) {
+        if (bkt->avg > THROTTLE_VALUE_MAX || bkt->max > THROTTLE_VALUE_MAX) {
             error_setg(errp, "bps/iops/max values must be within [0, %lld]",
                        THROTTLE_VALUE_MAX);
             return false;