Introduce latency histogram statics for block devices. For each accounted operation type latency region [0, +inf) is divided into subregions by several points. Then, calculate hits for each subregion.
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsement...@virtuozzo.com> --- include/block/accounting.h | 8 +++++ block/accounting.c | 83 ++++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 91 insertions(+) diff --git a/include/block/accounting.h b/include/block/accounting.h index b833d26d6c..7fbfc86c43 100644 --- a/include/block/accounting.h +++ b/include/block/accounting.h @@ -45,6 +45,12 @@ struct BlockAcctTimedStats { QSLIST_ENTRY(BlockAcctTimedStats) entries; }; +typedef struct BlockLatencyHistogram { + int size; + uint64_t *points; /* @size-1 points here (all points, except 0 and +inf) */ + uint64_t *histogram[BLOCK_MAX_IOTYPE]; /* @size elements for each type */ +} BlockLatencyHistogram; + struct BlockAcctStats { QemuMutex lock; uint64_t nr_bytes[BLOCK_MAX_IOTYPE]; @@ -57,6 +63,7 @@ struct BlockAcctStats { QSLIST_HEAD(, BlockAcctTimedStats) intervals; bool account_invalid; bool account_failed; + BlockLatencyHistogram latency_histogram; }; typedef struct BlockAcctCookie { @@ -82,5 +89,6 @@ void block_acct_merge_done(BlockAcctStats *stats, enum BlockAcctType type, int64_t block_acct_idle_time_ns(BlockAcctStats *stats); double block_acct_queue_depth(BlockAcctTimedStats *stats, enum BlockAcctType type); +int block_latency_histogram_set(BlockAcctStats *stats, uint64List *latency); #endif diff --git a/block/accounting.c b/block/accounting.c index 87ef5bbfaa..a34ef09015 100644 --- a/block/accounting.c +++ b/block/accounting.c @@ -94,6 +94,86 @@ void block_acct_start(BlockAcctStats *stats, BlockAcctCookie *cookie, cookie->type = type; } +/* block_latency_histogram_compare_func + * Compare @key with interval [@el, @el+1), where @el+1 is a next array element + * after @el. + * Return: -1 if @key < @el + * 0 if @key in [@el, @el+1) + * +1 if @key >= @el+1 + */ +static int block_latency_histogram_compare_func(const void *key, const void *el) +{ + uint64_t k = *(uint64_t *)key; + uint64_t a = *(uint64_t *)el; + uint64_t b = *((uint64_t *)el + 1); + + return k < a ? -1 : (k < b ? 0 : 1); +} + +static void block_latency_histogram_account(BlockLatencyHistogram *hist, + enum BlockAcctType type, + int64_t latency_ns) +{ + uint64_t *data, *pos; + + if (hist->points == NULL) { + /* histogram disabled */ + return; + } + + data = hist->histogram[type]; + + if (latency_ns < hist->points[0]) { + data[0]++; + return; + } + + if (latency_ns >= hist->points[hist->size - 2]) { + data[hist->size - 1]++; + return; + } + + pos = bsearch(&latency_ns, hist->points, hist->size - 2, + sizeof(hist->points[0]), + block_latency_histogram_compare_func); + assert(pos != NULL); + + data[pos - hist->points + 1]++; +} + +int block_latency_histogram_set(BlockAcctStats *stats, uint64List *latency) +{ + BlockLatencyHistogram *hist = &stats->latency_histogram; + uint64List *entry; + uint64_t *ptr; + int i; + uint64_t prev = 0; + + hist->size = 1; + + for (entry = latency; entry; entry = entry->next) { + if (entry->value <= prev) { + return -EINVAL; + } + hist->size++; + prev = entry->value; + } + + hist->points = g_renew(uint64_t, hist->points, hist->size - 1); + for (entry = latency, ptr = hist->points; entry; + entry = entry->next, ptr++) + { + *ptr = entry->value; + } + + for (i = 0; i < BLOCK_MAX_IOTYPE; i++) { + hist->histogram[i] = g_renew(uint64_t, hist->histogram[i], hist->size); + memset(hist->histogram[i], 0, hist->size * sizeof(uint64_t)); + } + + return 0; +} + static void block_account_one_io(BlockAcctStats *stats, BlockAcctCookie *cookie, bool failed) { @@ -116,6 +196,9 @@ static void block_account_one_io(BlockAcctStats *stats, BlockAcctCookie *cookie, stats->nr_ops[cookie->type]++; } + block_latency_histogram_account(&stats->latency_histogram, cookie->type, + latency_ns); + if (!failed || stats->account_failed) { stats->total_time_ns[cookie->type] += latency_ns; stats->last_access_time_ns = time_ns; -- 2.11.1