diff options
Diffstat (limited to 'util')
| -rw-r--r-- | util/oslib-posix.c | 2 | ||||
| -rw-r--r-- | util/throttle.c | 86 |
2 files changed, 36 insertions, 52 deletions
diff --git a/util/oslib-posix.c b/util/oslib-posix.c index cacf0ef5e3..80086c549f 100644 --- a/util/oslib-posix.c +++ b/util/oslib-posix.c @@ -530,6 +530,7 @@ void *qemu_alloc_stack(size_t *sz) ptr = mmap(NULL, *sz, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0); if (ptr == MAP_FAILED) { + perror("failed to allocate memory for stack"); abort(); } @@ -544,6 +545,7 @@ void *qemu_alloc_stack(size_t *sz) guardpage = ptr; #endif if (mprotect(guardpage, pagesz, PROT_NONE) != 0) { + perror("failed to set up stack guard page"); abort(); } diff --git a/util/throttle.c b/util/throttle.c index b2a52b8b34..b8c524336c 100644 --- a/util/throttle.c +++ b/util/throttle.c @@ -95,23 +95,36 @@ static int64_t throttle_do_compute_wait(double limit, double extra) int64_t throttle_compute_wait(LeakyBucket *bkt) { double extra; /* the number of extra units blocking the io */ + double bucket_size; /* I/O before throttling to bkt->avg */ + double burst_bucket_size; /* Before throttling to bkt->max */ if (!bkt->avg) { return 0; } - /* If the bucket is full then we have to wait */ - extra = bkt->level - bkt->max * bkt->burst_length; + if (!bkt->max) { + /* 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 = (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 = (double) bkt->max / 10; + } + + /* If the main bucket is full then we have to wait */ + extra = bkt->level - bucket_size; if (extra > 0) { return throttle_do_compute_wait(bkt->avg, extra); } - /* If the bucket is not full yet we have to make sure that we - * fulfill the goal of bkt->max units per second. */ + /* If the main bucket is not full yet we still have to check the + * burst bucket in order to enforce the burst limit */ if (bkt->burst_length > 1) { - /* We use 1/10 of the max value to smooth the throttling. - * See throttle_fix_bucket() for more details. */ - extra = bkt->burst_level - bkt->max / 10; + extra = bkt->burst_level - burst_bucket_size; if (extra > 0) { return throttle_do_compute_wait(bkt->max, extra); } @@ -324,32 +337,35 @@ bool throttle_is_valid(ThrottleConfig *cfg, Error **errp) } for (i = 0; i < BUCKETS_COUNT; i++) { - if (cfg->buckets[i].avg < 0 || - cfg->buckets[i].max < 0 || - cfg->buckets[i].avg > THROTTLE_VALUE_MAX || - cfg->buckets[i].max > THROTTLE_VALUE_MAX) { + LeakyBucket *bkt = &cfg->buckets[i]; + 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; } - if (!cfg->buckets[i].burst_length) { + if (!bkt->burst_length) { error_setg(errp, "the burst length cannot be 0"); return false; } - if (cfg->buckets[i].burst_length > 1 && !cfg->buckets[i].max) { + if (bkt->burst_length > 1 && !bkt->max) { error_setg(errp, "burst length set without burst rate"); return false; } - if (cfg->buckets[i].max && !cfg->buckets[i].avg) { + if (bkt->max && bkt->burst_length > THROTTLE_VALUE_MAX / bkt->max) { + error_setg(errp, "burst length too high for this burst rate"); + return false; + } + + if (bkt->max && !bkt->avg) { error_setg(errp, "bps_max/iops_max require corresponding" " bps/iops values"); return false; } - if (cfg->buckets[i].max && cfg->buckets[i].max < cfg->buckets[i].avg) { + if (bkt->max && bkt->max < bkt->avg) { error_setg(errp, "bps_max/iops_max cannot be lower than bps/iops"); return false; } @@ -358,36 +374,6 @@ bool throttle_is_valid(ThrottleConfig *cfg, Error **errp) return true; } -/* fix bucket parameters */ -static void throttle_fix_bucket(LeakyBucket *bkt) -{ - double min; - - /* zero bucket level */ - bkt->level = bkt->burst_level = 0; - - /* The following is done to cope with the Linux CFQ block scheduler - * which regroup reads and writes by block of 100ms in the guest. - * When they are two process one making reads and one making writes cfq - * make a pattern looking like the following: - * WWWWWWWWWWWRRRRRRRRRRRRRRWWWWWWWWWWWWWwRRRRRRRRRRRRRRRRR - * Having a max burst value of 100ms of the average will help smooth the - * throttling - */ - min = bkt->avg / 10; - if (bkt->avg && !bkt->max) { - bkt->max = min; - } -} - -/* undo internal bucket parameter changes (see throttle_fix_bucket()) */ -static void throttle_unfix_bucket(LeakyBucket *bkt) -{ - if (bkt->max < bkt->avg) { - bkt->max = 0; - } -} - /* Used to configure the throttle * * @ts: the throttle state we are working on @@ -402,8 +388,10 @@ void throttle_config(ThrottleState *ts, ts->cfg = *cfg; + /* Zero bucket level */ for (i = 0; i < BUCKETS_COUNT; i++) { - throttle_fix_bucket(&ts->cfg.buckets[i]); + ts->cfg.buckets[i].level = 0; + ts->cfg.buckets[i].burst_level = 0; } ts->previous_leak = qemu_clock_get_ns(clock_type); @@ -416,13 +404,7 @@ 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]); - } } |