[Qemu-devel] [PATCH v4 0/2] block latency histogram

[Qemu-devel] [PATCH v4 0/2] block latency histogram

[Vladimir Sementsov-Ogievskiy]

v4:

Move block_latency_histogram_set from block/accounting.c to
blockdev.c, as it uses qapi type uint64List and this fact breaks
build.


v3:

- semantics, naming and wording changed a lot
- x prefixes added to new qapi names
- bug fixed about calculation of new_size (new_nbins now)
- drop g_renew
- in _clear() set nbinst to zero too

v2:

01: add block_latency_histogram_clear()
02: fix spelling (sorry =()
    some rewordings
    remove histogram if latency parameter unspecified

Vladimir Sementsov-Ogievskiy (2):
  block/accounting: introduce latency histogram
  qapi: add block latency histogram interface

 qapi/block-core.json       | 111 ++++++++++++++++++++++++++++++++++++++++++++-
 include/block/accounting.h |  32 +++++++++++++
 block/accounting.c         |  59 ++++++++++++++++++++++++
 block/qapi.c               |  41 +++++++++++++++++
 blockdev.c                 |  76 +++++++++++++++++++++++++++++++
 5 files changed, 318 insertions(+), 1 deletion(-)

-- 
2.11.1

[Qemu-devel] [PATCH v4 1/2] block/accounting: introduce latency histogram

[Vladimir Sementsov-Ogievskiy]

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 <vsementsov@virtuozzo.com>
---
 include/block/accounting.h | 32 +++++++++++++++++++++++++
 block/accounting.c         | 59 ++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 91 insertions(+)

diff --git a/include/block/accounting.h b/include/block/accounting.h
index b833d26d6c..e23951619e 100644
--- a/include/block/accounting.h
+++ b/include/block/accounting.h
@@ -45,6 +45,36 @@ struct BlockAcctTimedStats {
     QSLIST_ENTRY(BlockAcctTimedStats) entries;
 };
 
+typedef struct BlockLatencyHistogram {
+    /* The following histogram is represented like this:
+     *
+     * 5|           *
+     * 4|           *
+     * 3| *         *
+     * 2| *         *    *
+     * 1| *    *    *    *
+     *  +------------------
+     *      10   50   100
+     *
+     * BlockLatencyHistogram histogram = {
+     *     .nbins = 4,
+     *     .boundaries = {10, 50, 100},
+     *     .bins = {3, 1, 5, 2},
+     * };
+     *
+     * @boundaries array define histogram intervals as follows:
+     * [0, boundaries[0]), [boundaries[0], boundaries[1]), ...
+     * [boundaries[nbins-2], +inf)
+     *
+     * So, for example above, histogram intervals are:
+     * [0, 10), [10, 50), [50, 100), [100, +inf)
+     */
+    int nbins;
+    uint64_t *boundaries; /* @nbins-1 numbers here
+                             (all boundaries, except 0 and +inf) */
+    uint64_t *bins;
+} BlockLatencyHistogram;
+
 struct BlockAcctStats {
     QemuMutex lock;
     uint64_t nr_bytes[BLOCK_MAX_IOTYPE];
@@ -57,6 +87,7 @@ struct BlockAcctStats {
     QSLIST_HEAD(, BlockAcctTimedStats) intervals;
     bool account_invalid;
     bool account_failed;
+    BlockLatencyHistogram latency_histogram[BLOCK_MAX_IOTYPE];
 };
 
 typedef struct BlockAcctCookie {
@@ -82,5 +113,6 @@ 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);
+void block_latency_histograms_clear(BlockAcctStats *stats);
 
 #endif
diff --git a/block/accounting.c b/block/accounting.c
index 87ef5bbfaa..26a880bc6d 100644
--- a/block/accounting.c
+++ b/block/accounting.c
@@ -94,6 +94,62 @@ 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]++;
+}
+
+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 +172,9 @@ 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

[Qemu-devel] [PATCH v4 2/2] qapi: add block latency histogram interface

[Vladimir Sementsov-Ogievskiy]

Set (and clear) histogram through new command
block-latency-histogram-set and show new statistics in
query-blockstats results.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
---
 qapi/block-core.json | 111 ++++++++++++++++++++++++++++++++++++++++++++++++++-
 block/qapi.c         |  41 +++++++++++++++++++
 blockdev.c           |  76 +++++++++++++++++++++++++++++++++++
 3 files changed, 227 insertions(+), 1 deletion(-)

diff --git a/qapi/block-core.json b/qapi/block-core.json
index 8225308904..fd4c13ad8a 100644
--- a/qapi/block-core.json
+++ b/qapi/block-core.json
@@ -451,6 +451,106 @@
            'status': 'DirtyBitmapStatus'} }
 
 ##
+# @XBlockLatencyHistogramInfo:
+#
+# Block latency histogram.
+#
+# @boundaries: list of interval boundary values in nanoseconds, all greater
+#              than zero and in ascending order.
+#              For example, the list [10, 50, 100] produces the following
+#              histogram intervals: [0, 10), [10, 50), [50, 100), [100, +inf).
+#
+# @bins: list of io request counts corresponding to histogram intervals.
+#        len(@bins) = len(@boundaries) + 1
+#        For the example above, @bins may be something like [3, 1, 5, 2],
+#        and corresponding histogram looks like:
+#
+#        5|           *
+#        4|           *
+#        3| *         *
+#        2| *         *    *
+#        1| *    *    *    *
+#         +------------------
+#             10   50   100
+#
+# Since: 2.12
+##
+{ 'struct': 'XBlockLatencyHistogramInfo',
+  'data': {'boundaries': ['uint64'], 'bins': ['uint64'] } }
+
+##
+# @x-block-latency-histogram-set:
+#
+# Manage read, write and flush latency histograms for the device.
+#
+# If only @device parameter is specified, remove all present latency histograms
+# for the device. Otherwise, add/reset some of (or all) latency histograms.
+#
+# @device: device name to set latency histogram for.
+#
+# @boundaries: list of interval boundary values (see description in
+#              XBlockLatencyHistogramInfo definition). If specified, all
+#              latency histograms are removed, and empty ones created for all
+#              io types with intervals corresponding to @boundaries (except for
+#              io types, for which specific boundaries are set through the
+#              following parameters).
+#
+# @boundaries-read: list of interval boundary values for read latency
+#                   histogram. If specified, old read latency histogram is
+#                   removed, and empty one created with interavals
+#                   corresponding to @boundaries-read. The parameter has higher
+#                   priority then @boundaries.
+#
+# @boundaries-write: list of interaval boundary values for write latency
+#                    histogram.
+#
+# @boundaries-flush: list of interaval boundary values for flush latency
+#                    histogram.
+#
+# Returns: error if device is not found or @boundaries* arrays are invalid.
+#
+# Since: 2.12
+#
+# Example: set new histograms for all io types with intervals
+# [0, 10), [10, 50), [50, 100), [100, +inf):
+#
+# -> { "execute": "block-latency-histogram-set",
+#      "arguments": { "device": "drive0",
+#                     "boundaries": [10, 50, 100] } }
+# <- { "return": {} }
+#
+# Example: set new histogram only for write, other histograms will remain
+# not changed (or not created):
+#
+# -> { "execute": "block-latency-histogram-set",
+#      "arguments": { "device": "drive0",
+#                     "boundaries-write": [10, 50, 100] } }
+# <- { "return": {} }
+#
+# Example: set new histograms with the following intervals:
+#   read, flush: [0, 10), [10, 50), [50, 100), [100, +inf)
+#   write: [0, 1000), [1000, 5000), [5000, +inf)
+#
+# -> { "execute": "block-latency-histogram-set",
+#      "arguments": { "device": "drive0",
+#                     "boundaries": [10, 50, 100],
+#                     "boundaries-write": [1000, 5000] } }
+# <- { "return": {} }
+#
+# Example: remove all latency histograms:
+#
+# -> { "execute": "block-latency-histogram-set",
+#      "arguments": { "device": "drive0" } }
+# <- { "return": {} }
+##
+{ 'command': 'x-block-latency-histogram-set',
+  'data': {'device': 'str',
+           '*boundaries': ['uint64'],
+           '*boundaries-read': ['uint64'],
+           '*boundaries-write': ['uint64'],
+           '*boundaries-flush': ['uint64'] } }
+
+##
 # @BlockInfo:
 #
 # Block device information.  This structure describes a virtual device and
@@ -730,6 +830,12 @@
 # @timed_stats: Statistics specific to the set of previously defined
 #               intervals of time (Since 2.5)
 #
+# @x_rd_latency_histogram: @BlockLatencyHistogramInfo. (Since 2.12)
+#
+# @x_wr_latency_histogram: @BlockLatencyHistogramInfo. (Since 2.12)
+#
+# @x_flush_latency_histogram: @BlockLatencyHistogramInfo. (Since 2.12)
+#
 # Since: 0.14.0
 ##
 { 'struct': 'BlockDeviceStats',
@@ -742,7 +848,10 @@
            'failed_flush_operations': 'int', 'invalid_rd_operations': 'int',
            'invalid_wr_operations': 'int', 'invalid_flush_operations': 'int',
            'account_invalid': 'bool', 'account_failed': 'bool',
-           'timed_stats': ['BlockDeviceTimedStats'] } }
+           'timed_stats': ['BlockDeviceTimedStats'],
+           '*x_rd_latency_histogram': 'XBlockLatencyHistogramInfo',
+           '*x_wr_latency_histogram': 'XBlockLatencyHistogramInfo',
+           '*x_flush_latency_histogram': 'XBlockLatencyHistogramInfo' } }
 
 ##
 # @BlockStats:
diff --git a/block/qapi.c b/block/qapi.c
index fc10f0a565..4bddf48e50 100644
--- a/block/qapi.c
+++ b/block/qapi.c
@@ -389,6 +389,37 @@ static void bdrv_query_info(BlockBackend *blk, BlockInfo **p_info,
     qapi_free_BlockInfo(info);
 }
 
+static uint64List *uint64_list(uint64_t *list, int size)
+{
+    int i;
+    uint64List *out_list = NULL;
+    uint64List **pout_list = &out_list;
+
+    for (i = 0; i < size; i++) {
+        uint64List *entry = g_new(uint64List, 1);
+        entry->value = list[i];
+        *pout_list = entry;
+        pout_list = &entry->next;
+    }
+
+    *pout_list = NULL;
+
+    return out_list;
+}
+
+static void bdrv_latency_histogram_stats(BlockLatencyHistogram *hist,
+                                         bool *not_null,
+                                         XBlockLatencyHistogramInfo **info)
+{
+    *not_null = hist->bins != NULL;
+    if (*not_null) {
+        *info = g_new0(XBlockLatencyHistogramInfo, 1);
+
+        (*info)->boundaries = uint64_list(hist->boundaries, hist->nbins - 1);
+        (*info)->bins = uint64_list(hist->bins, hist->nbins);
+    }
+}
+
 static void bdrv_query_blk_stats(BlockDeviceStats *ds, BlockBackend *blk)
 {
     BlockAcctStats *stats = blk_get_stats(blk);
@@ -454,6 +485,16 @@ static void bdrv_query_blk_stats(BlockDeviceStats *ds, BlockBackend *blk)
         dev_stats->avg_wr_queue_depth =
             block_acct_queue_depth(ts, BLOCK_ACCT_WRITE);
     }
+
+    bdrv_latency_histogram_stats(&stats->latency_histogram[BLOCK_ACCT_READ],
+                                 &ds->has_x_rd_latency_histogram,
+                                 &ds->x_rd_latency_histogram);
+    bdrv_latency_histogram_stats(&stats->latency_histogram[BLOCK_ACCT_WRITE],
+                                 &ds->has_x_wr_latency_histogram,
+                                 &ds->x_wr_latency_histogram);
+    bdrv_latency_histogram_stats(&stats->latency_histogram[BLOCK_ACCT_FLUSH],
+                                 &ds->has_x_flush_latency_histogram,
+                                 &ds->x_flush_latency_histogram);
 }
 
 static BlockStats *bdrv_query_bds_stats(BlockDriverState *bs,
diff --git a/blockdev.c b/blockdev.c
index 8e977eef11..9d7d56ca81 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -4176,6 +4176,82 @@ void qmp_x_blockdev_set_iothread(const char *node_name, StrOrNull *iothread,
     aio_context_release(old_context);
 }
 
+static 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 qmp_x_block_latency_histogram_set(
+    const char *device,
+    bool has_boundaries, uint64List *boundaries,
+    bool has_boundaries_read, uint64List *boundaries_read,
+    bool has_boundaries_write, uint64List *boundaries_write,
+    bool has_boundaries_flush, uint64List *boundaries_flush,
+    Error **errp)
+{
+    BlockBackend *blk = blk_by_name(device);
+    BlockAcctStats *stats;
+
+    if (!blk) {
+        error_setg(errp, "Device '%s' not found", device);
+        return;
+    }
+    stats = blk_get_stats(blk);
+
+    if (!has_boundaries && !has_boundaries_read && !has_boundaries_write &&
+        !has_boundaries_flush)
+    {
+        block_latency_histograms_clear(stats);
+        return;
+    }
+
+    if (has_boundaries || has_boundaries_read) {
+        block_latency_histogram_set(
+            stats, BLOCK_ACCT_READ,
+            has_boundaries_read ? boundaries_read : boundaries);
+    }
+
+    if (has_boundaries || has_boundaries_write) {
+        block_latency_histogram_set(
+            stats, BLOCK_ACCT_WRITE,
+            has_boundaries_write ? boundaries_write : boundaries);
+    }
+
+    if (has_boundaries || has_boundaries_flush) {
+        block_latency_histogram_set(
+            stats, BLOCK_ACCT_FLUSH,
+            has_boundaries_flush ? boundaries_flush : boundaries);
+    }
+}
+
 QemuOptsList qemu_common_drive_opts = {
     .name = "drive",
     .head = QTAILQ_HEAD_INITIALIZER(qemu_common_drive_opts.head),
-- 
2.11.1

Re: [Qemu-devel] [PATCH v4 0/2] block latency histogram

[Eric Blake]

On 03/09/2018 09:33 AM, Vladimir Sementsov-Ogievskiy wrote:
> v4:
> 
> Move block_latency_histogram_set from block/accounting.c to
> blockdev.c, as it uses qapi type uint64List and this fact breaks
> build.

Was the cross file motion necessary, or could you just fix the #includes 
according to the recent qapi header refactoring?

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org

Re: [Qemu-devel] [PATCH v4 0/2] block latency histogram

[Vladimir Sementsov-Ogievskiy]

09.03.2018 18:40, Eric Blake wrote:
> On 03/09/2018 09:33 AM, Vladimir Sementsov-Ogievskiy wrote:
>> v4:
>>
>> Move block_latency_histogram_set from block/accounting.c to
>> blockdev.c, as it uses qapi type uint64List and this fact breaks
>> build.
>
> Was the cross file motion necessary, or could you just fix the 
> #includes according to the recent qapi header refactoring?
>

Looks like it's not as simple..

/tmp/qemu-test/src/include/block/accounting.h:30:10: fatal error: qapi-types.h: No such file or directory
  #include "qapi-types.h


what to do now? Looks like qapi-types are not generated for some builds. So, this version (v4) should take place.

-- 
Best regards,
Vladimir

Re: [Qemu-devel] [PATCH v4 0/2] block latency histogram

[Eric Blake]

On 03/09/2018 10:31 AM, Vladimir Sementsov-Ogievskiy wrote:
> 09.03.2018 18:40, Eric Blake wrote:
>> On 03/09/2018 09:33 AM, Vladimir Sementsov-Ogievskiy wrote:
>>> v4:
>>>
>>> Move block_latency_histogram_set from block/accounting.c to
>>> blockdev.c, as it uses qapi type uint64List and this fact breaks
>>> build.
>>
>> Was the cross file motion necessary, or could you just fix the 
>> #includes according to the recent qapi header refactoring?
>>
> 
> Looks like it's not as simple..
> 
> /tmp/qemu-test/src/include/block/accounting.h:30:10: fatal error: 
> qapi-types.h: No such file or directory
>   #include "qapi-types.h
> 
> 
> what to do now? Looks like qapi-types are not generated for some builds. 
> So, this version (v4) should take place.

top-level qapi-types.h was replaced by lots of qapi/qapi*.h modular 
headers.  Unfortunately, incremental builds don't delete the stale 
qapi-types.h that was left in tree from the point prior to the qapi 
header refactoring.

To get uint64List, use qapi/qapi-builtin-types.h.  To get any type 
defined in a qapi/MODULE.json file, use qapi/qapi-MODULE-types.h.

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org

Re: [Qemu-devel] [PATCH v4 0/2] block latency histogram

[Vladimir Sementsov-Ogievskiy]

09.03.2018 19:37, Eric Blake wrote:
> On 03/09/2018 10:31 AM, Vladimir Sementsov-Ogievskiy wrote:
>> 09.03.2018 18:40, Eric Blake wrote:
>>> On 03/09/2018 09:33 AM, Vladimir Sementsov-Ogievskiy wrote:
>>>> v4:
>>>>
>>>> Move block_latency_histogram_set from block/accounting.c to
>>>> blockdev.c, as it uses qapi type uint64List and this fact breaks
>>>> build.
>>>
>>> Was the cross file motion necessary, or could you just fix the 
>>> #includes according to the recent qapi header refactoring?
>>>
>>
>> Looks like it's not as simple..
>>
>> /tmp/qemu-test/src/include/block/accounting.h:30:10: fatal error: 
>> qapi-types.h: No such file or directory
>>   #include "qapi-types.h
>>
>>
>> what to do now? Looks like qapi-types are not generated for some 
>> builds. So, this version (v4) should take place.
>
> top-level qapi-types.h was replaced by lots of qapi/qapi*.h modular 
> headers.  Unfortunately, incremental builds don't delete the stale 
> qapi-types.h that was left in tree from the point prior to the qapi 
> header refactoring.
>
> To get uint64List, use qapi/qapi-builtin-types.h.  To get any type 
> defined in a qapi/MODULE.json file, use qapi/qapi-MODULE-types.h.
>

thanks, now it works, after git clean..

-- 
Best regards,
Vladimir