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authorVladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>2018-03-09 19:52:11 +0300
committerEric Blake <eblake@redhat.com>2018-03-19 14:58:37 -0500
commitb741ae74170643de0fec3005c717e3a397c3e034 (patch)
treed16b50a589fb7f94c48970612b84f1bac84903d6 /block/accounting.c
parentd003f7a8f9cafe50119975844fa01afc2baf41fb (diff)
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block/accounting: introduce latency histogram
Introduce latency histogram statics for block devices. For each accounted operation type, the latency region [0, +inf) is divided into subregions by several points. Then, calculate hits for each subregion. Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com> Message-Id: <20180309165212.97144-2-vsementsov@virtuozzo.com> Reviewed-by: Eric Blake <eblake@redhat.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Signed-off-by: Eric Blake <eblake@redhat.com>
Diffstat (limited to 'block/accounting.c')
-rw-r--r--block/accounting.c91
1 files changed, 91 insertions, 0 deletions
diff --git a/block/accounting.c b/block/accounting.c
index 87ef5bb..70a3d9a 100644
--- a/block/accounting.c
+++ b/block/accounting.c
@@ -94,6 +94,94 @@ void block_acct_start(BlockAcctStats *stats, BlockAcctCookie *cookie,
cookie->type = type;
}
+/* block_latency_histogram_compare_func:
+ * Compare @key with interval [@it[0], @it[1]).
+ * Return: -1 if @key < @it[0]
+ * 0 if @key in [@it[0], @it[1])
+ * +1 if @key >= @it[1]
+ */
+static int block_latency_histogram_compare_func(const void *key, const void *it)
+{
+ uint64_t k = *(uint64_t *)key;
+ uint64_t a = ((uint64_t *)it)[0];
+ uint64_t b = ((uint64_t *)it)[1];
+
+ return k < a ? -1 : (k < b ? 0 : 1);
+}
+
+static void block_latency_histogram_account(BlockLatencyHistogram *hist,
+ int64_t latency_ns)
+{
+ uint64_t *pos;
+
+ if (hist->bins == NULL) {
+ /* histogram disabled */
+ return;
+ }
+
+
+ if (latency_ns < hist->boundaries[0]) {
+ hist->bins[0]++;
+ return;
+ }
+
+ if (latency_ns >= hist->boundaries[hist->nbins - 2]) {
+ hist->bins[hist->nbins - 1]++;
+ return;
+ }
+
+ pos = bsearch(&latency_ns, hist->boundaries, hist->nbins - 2,
+ sizeof(hist->boundaries[0]),
+ block_latency_histogram_compare_func);
+ assert(pos != NULL);
+
+ hist->bins[pos - hist->boundaries + 1]++;
+}
+
+int block_latency_histogram_set(BlockAcctStats *stats, enum BlockAcctType type,
+ uint64List *boundaries)
+{
+ BlockLatencyHistogram *hist = &stats->latency_histogram[type];
+ uint64List *entry;
+ uint64_t *ptr;
+ uint64_t prev = 0;
+ int new_nbins = 1;
+
+ for (entry = boundaries; entry; entry = entry->next) {
+ if (entry->value <= prev) {
+ return -EINVAL;
+ }
+ new_nbins++;
+ prev = entry->value;
+ }
+
+ hist->nbins = new_nbins;
+ g_free(hist->boundaries);
+ hist->boundaries = g_new(uint64_t, hist->nbins - 1);
+ for (entry = boundaries, ptr = hist->boundaries; entry;
+ entry = entry->next, ptr++)
+ {
+ *ptr = entry->value;
+ }
+
+ g_free(hist->bins);
+ hist->bins = g_new0(uint64_t, hist->nbins);
+
+ return 0;
+}
+
+void block_latency_histograms_clear(BlockAcctStats *stats)
+{
+ int i;
+
+ for (i = 0; i < BLOCK_MAX_IOTYPE; i++) {
+ BlockLatencyHistogram *hist = &stats->latency_histogram[i];
+ g_free(hist->bins);
+ g_free(hist->boundaries);
+ memset(hist, 0, sizeof(*hist));
+ }
+}
+
static void block_account_one_io(BlockAcctStats *stats, BlockAcctCookie *cookie,
bool failed)
{
@@ -116,6 +204,9 @@ 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;