[PATCH v2 0/3] block: add logging facility for long standing IO requests

[PATCH v2 0/3] block: add logging facility for long standing IO requests

[Denis V. Lunev]

There are severe delays with IO requests processing if QEMU is running in
virtual machine or over software defined storage. Such delays potentially
results in unpredictable guest behavior. For example, guests over IDE or
SATA drive could remount filesystem read-only if write is performed
longer than 10 seconds.

Such reports are very complex to process. Some good starting point for this
seems quite reasonable. This patch provides one. It adds logging of such
potentially dangerous long IO operations.

Changes from v1:
- fixed conversions using macros suggested by Stefan
- fixed option declaration
- enabled by default with patch 3

Signed-off-by: Denis V. Lunev <den@openvz.org>
CC: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
CC: Kevin Wolf <kwolf@redhat.com>
CC: Max Reitz <mreitz@redhat.com>
CC: Stefan Hajnoczi <stefanha@redhat.com>

[PATCH 1/3] block/block-backend: add converter from BlockAcctStats to BlockBackend

[Denis V. Lunev]

Right now BlockAcctStats is always reside on BlockBackend. This structure
is not used in any other place. Thus we are able to create a converter
from one pointer to another.

Signed-off-by: Denis V. Lunev <den@openvz.org>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
CC: Stefan Hajnoczi <stefanha@redhat.com>
CC: Kevin Wolf <kwolf@redhat.com>
CC: Max Reitz <mreitz@redhat.com>
---
 block/block-backend.c          | 5 +++++
 include/sysemu/block-backend.h | 1 +
 2 files changed, 6 insertions(+)

diff --git a/block/block-backend.c b/block/block-backend.c
index 3a13cb5f0b..88e531df98 100644
--- a/block/block-backend.c
+++ b/block/block-backend.c
@@ -2153,6 +2153,11 @@ BlockAcctStats *blk_get_stats(BlockBackend *blk)
     return &blk->stats;
 }
 
+BlockBackend *blk_stats2blk(BlockAcctStats *s)
+{
+    return container_of(s, BlockBackend, stats);
+}
+
 void *blk_aio_get(const AIOCBInfo *aiocb_info, BlockBackend *blk,
                   BlockCompletionFunc *cb, void *opaque)
 {
diff --git a/include/sysemu/block-backend.h b/include/sysemu/block-backend.h
index 8203d7f6f9..bd4694e7bc 100644
--- a/include/sysemu/block-backend.h
+++ b/include/sysemu/block-backend.h
@@ -227,6 +227,7 @@ void blk_add_insert_bs_notifier(BlockBackend *blk, Notifier *notify);
 void blk_io_plug(BlockBackend *blk);
 void blk_io_unplug(BlockBackend *blk);
 BlockAcctStats *blk_get_stats(BlockBackend *blk);
+BlockBackend *blk_stats2blk(BlockAcctStats *stats);
 BlockBackendRootState *blk_get_root_state(BlockBackend *blk);
 void blk_update_root_state(BlockBackend *blk);
 bool blk_get_detect_zeroes_from_root_state(BlockBackend *blk);
-- 
2.17.1

[PATCH 2/3] block: add logging facility for long standing IO requests

[Denis V. Lunev]

There are severe delays with IO requests processing if QEMU is running in
virtual machine or over software defined storage. Such delays potentially
results in unpredictable guest behavior. For example, guests over IDE or
SATA drive could remount filesystem read-only if write is performed
longer than 10 seconds.

Such reports are very complex to process. Some good starting point for this
seems quite reasonable. This patch provides one. It adds logging of such
potentially dangerous long IO operations.

Signed-off-by: Denis V. Lunev <den@openvz.org>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
CC: Stefan Hajnoczi <stefanha@redhat.com>
CC: Kevin Wolf <kwolf@redhat.com>
CC: Max Reitz <mreitz@redhat.com>
---
 block/accounting.c         | 59 +++++++++++++++++++++++++++++++++++++-
 blockdev.c                 |  7 ++++-
 include/block/accounting.h |  5 +++-
 slirp                      |  2 +-
 4 files changed, 69 insertions(+), 4 deletions(-)

diff --git a/block/accounting.c b/block/accounting.c
index 8d41c8a83a..24f48c84b8 100644
--- a/block/accounting.c
+++ b/block/accounting.c
@@ -27,7 +27,9 @@
 #include "block/accounting.h"
 #include "block/block_int.h"
 #include "qemu/timer.h"
+#include "qemu/log.h"
 #include "sysemu/qtest.h"
+#include "sysemu/block-backend.h"
 
 static QEMUClockType clock_type = QEMU_CLOCK_REALTIME;
 static const int qtest_latency_ns = NANOSECONDS_PER_SECOND / 1000;
@@ -41,10 +43,11 @@ void block_acct_init(BlockAcctStats *stats)
 }
 
 void block_acct_setup(BlockAcctStats *stats, bool account_invalid,
-                      bool account_failed)
+                      bool account_failed, unsigned latency_log_threshold_ms)
 {
     stats->account_invalid = account_invalid;
     stats->account_failed = account_failed;
+    stats->latency_log_threshold_ms = latency_log_threshold_ms;
 }
 
 void block_acct_cleanup(BlockAcctStats *stats)
@@ -182,6 +185,58 @@ void block_latency_histograms_clear(BlockAcctStats *stats)
     }
 }
 
+static const char *block_account_type(enum BlockAcctType type)
+{
+    switch (type) {
+    case BLOCK_ACCT_READ:
+        return "READ";
+    case BLOCK_ACCT_WRITE:
+        return "WRITE";
+    case BLOCK_ACCT_FLUSH:
+        return "DISCARD";
+    case BLOCK_ACCT_UNMAP:
+        return "TRUNCATE";
+    case BLOCK_ACCT_NONE:
+        return "NONE";
+    case BLOCK_MAX_IOTYPE:
+        break;
+    }
+    return "UNKNOWN";
+}
+
+static void block_acct_report_long(BlockAcctStats *stats,
+                                   BlockAcctCookie *cookie, int64_t latency_ns)
+{
+    unsigned latency_ms = latency_ns / SCALE_MS;
+    int64_t start_time_host_s;
+    char buf[64];
+    struct tm t;
+    BlockDriverState *bs;
+
+    if (cookie->type == BLOCK_ACCT_NONE) {
+        return;
+    }
+    if (stats->latency_log_threshold_ms == 0) {
+        return;
+    }
+    if (latency_ms < stats->latency_log_threshold_ms) {
+        return;
+    }
+
+    start_time_host_s = cookie->start_time_ns / NANOSECONDS_PER_SECOND;
+    strftime(buf, sizeof(buf), "%m-%d %H:%M:%S",
+             localtime_r(&start_time_host_s, &t));
+
+    bs = blk_bs(blk_stats2blk(stats));
+    qemu_log("long %s[%ld] IO request: %d.03%d since %s.%03d bs: %s(%s, %s)\n",
+             block_account_type(cookie->type), cookie->bytes,
+             (int)(latency_ms / 1000), (int)(latency_ms % 1000), buf,
+             (int)((cookie->start_time_ns / 1000000) % 1000),
+             bs == NULL ? "unknown" : bdrv_get_node_name(bs),
+             bs == NULL ? "unknown" : bdrv_get_format_name(bs),
+             bs == NULL ? "unknown" : bs->filename);
+}
+
 static void block_account_one_io(BlockAcctStats *stats, BlockAcctCookie *cookie,
                                  bool failed)
 {
@@ -222,6 +277,8 @@ static void block_account_one_io(BlockAcctStats *stats, BlockAcctCookie *cookie,
 
     qemu_mutex_unlock(&stats->lock);
 
+    block_acct_report_long(stats, cookie, latency_ns);
+
     cookie->type = BLOCK_ACCT_NONE;
 }
 
diff --git a/blockdev.c b/blockdev.c
index 3848a9c8ab..66158d1292 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -622,7 +622,8 @@ static BlockBackend *blockdev_init(const char *file, QDict *bs_opts,
 
         bs->detect_zeroes = detect_zeroes;
 
-        block_acct_setup(blk_get_stats(blk), account_invalid, account_failed);
+        block_acct_setup(blk_get_stats(blk), account_invalid, account_failed,
+                qemu_opt_get_number(opts, "latency-log-threshold", 0));
 
         if (!parse_stats_intervals(blk_get_stats(blk), interval_list, errp)) {
             blk_unref(blk);
@@ -3727,6 +3728,10 @@ QemuOptsList qemu_common_drive_opts = {
             .type = QEMU_OPT_BOOL,
             .help = "whether to account for failed I/O operations "
                     "in the statistics",
+        },{
+            .name = "latency-log-threshold",
+            .type = QEMU_OPT_NUMBER,
+            .help = "threshold for long I/O report (disabled if <=0), in ms",
         },
         { /* end of list */ }
     },
diff --git a/include/block/accounting.h b/include/block/accounting.h
index 878b4c3581..c3ea25f9aa 100644
--- a/include/block/accounting.h
+++ b/include/block/accounting.h
@@ -91,6 +91,9 @@ struct BlockAcctStats {
     bool account_invalid;
     bool account_failed;
     BlockLatencyHistogram latency_histogram[BLOCK_MAX_IOTYPE];
+
+    /* Threshold for long I/O detection, ms */
+    unsigned latency_log_threshold_ms;
 };
 
 typedef struct BlockAcctCookie {
@@ -101,7 +104,7 @@ typedef struct BlockAcctCookie {
 
 void block_acct_init(BlockAcctStats *stats);
 void block_acct_setup(BlockAcctStats *stats, bool account_invalid,
-                     bool account_failed);
+                      bool account_failed, unsigned latency_log_threshold_ms);
 void block_acct_cleanup(BlockAcctStats *stats);
 void block_acct_add_interval(BlockAcctStats *stats, unsigned interval_length);
 BlockAcctTimedStats *block_acct_interval_next(BlockAcctStats *stats,
diff --git a/slirp b/slirp
index ce94eba204..2faae0f778 160000
--- a/slirp
+++ b/slirp
@@ -1 +1 @@
-Subproject commit ce94eba2042d52a0ba3d9e252ebce86715e94275
+Subproject commit 2faae0f778f818fadc873308f983289df697eb93
-- 
2.17.1

[PATCH 3/3] block: enable long IO requests report by default

[Denis V. Lunev]

Latency threshold is set to 10 seconds following guest request timeout
on legacy storage controller.

Signed-off-by: Denis V. Lunev <den@openvz.org>
CC: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
CC: Stefan Hajnoczi <stefanha@redhat.com>
CC: Kevin Wolf <kwolf@redhat.com>
CC: Max Reitz <mreitz@redhat.com>
---
 blockdev.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/blockdev.c b/blockdev.c
index 66158d1292..9eb58efc2b 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -623,7 +623,8 @@ static BlockBackend *blockdev_init(const char *file, QDict *bs_opts,
         bs->detect_zeroes = detect_zeroes;
 
         block_acct_setup(blk_get_stats(blk), account_invalid, account_failed,
-                qemu_opt_get_number(opts, "latency-log-threshold", 0));
+                qemu_opt_get_number(opts, "latency-log-threshold",
+                                    10000 /* ms */));
 
         if (!parse_stats_intervals(blk_get_stats(blk), interval_list, errp)) {
             blk_unref(blk);
-- 
2.17.1

Re: [PATCH 2/3] block: add logging facility for long standing IO requests

[Philippe Mathieu-Daudé]

On 8/5/20 12:08 PM, Denis V. Lunev wrote:
> There are severe delays with IO requests processing if QEMU is running in
> virtual machine or over software defined storage. Such delays potentially
> results in unpredictable guest behavior. For example, guests over IDE or
> SATA drive could remount filesystem read-only if write is performed
> longer than 10 seconds.
> 
> Such reports are very complex to process. Some good starting point for this
> seems quite reasonable. This patch provides one. It adds logging of such
> potentially dangerous long IO operations.
> 
> Signed-off-by: Denis V. Lunev <den@openvz.org>
> Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
> CC: Stefan Hajnoczi <stefanha@redhat.com>
> CC: Kevin Wolf <kwolf@redhat.com>
> CC: Max Reitz <mreitz@redhat.com>
> ---
>  block/accounting.c         | 59 +++++++++++++++++++++++++++++++++++++-
>  blockdev.c                 |  7 ++++-
>  include/block/accounting.h |  5 +++-
>  slirp                      |  2 +-
>  4 files changed, 69 insertions(+), 4 deletions(-)
> 
...

>  typedef struct BlockAcctCookie {
> @@ -101,7 +104,7 @@ typedef struct BlockAcctCookie {
>  
>  void block_acct_init(BlockAcctStats *stats);
>  void block_acct_setup(BlockAcctStats *stats, bool account_invalid,
> -                     bool account_failed);
> +                      bool account_failed, unsigned latency_log_threshold_ms);
>  void block_acct_cleanup(BlockAcctStats *stats);
>  void block_acct_add_interval(BlockAcctStats *stats, unsigned interval_length);
>  BlockAcctTimedStats *block_acct_interval_next(BlockAcctStats *stats,
> diff --git a/slirp b/slirp
> index ce94eba204..2faae0f778 160000
> --- a/slirp
> +++ b/slirp
> @@ -1 +1 @@
> -Subproject commit ce94eba2042d52a0ba3d9e252ebce86715e94275
> +Subproject commit 2faae0f778f818fadc873308f983289df697eb93

SLiRP change unrelated I presume...

Re: [PATCH 2/3] block: add logging facility for long standing IO requests

[Denis V. Lunev]

On 8/5/20 4:51 PM, Philippe Mathieu-Daudé wrote:
> On 8/5/20 12:08 PM, Denis V. Lunev wrote:
>> There are severe delays with IO requests processing if QEMU is running in
>> virtual machine or over software defined storage. Such delays potentially
>> results in unpredictable guest behavior. For example, guests over IDE or
>> SATA drive could remount filesystem read-only if write is performed
>> longer than 10 seconds.
>>
>> Such reports are very complex to process. Some good starting point for this
>> seems quite reasonable. This patch provides one. It adds logging of such
>> potentially dangerous long IO operations.
>>
>> Signed-off-by: Denis V. Lunev <den@openvz.org>
>> Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
>> CC: Stefan Hajnoczi <stefanha@redhat.com>
>> CC: Kevin Wolf <kwolf@redhat.com>
>> CC: Max Reitz <mreitz@redhat.com>
>> ---
>>  block/accounting.c         | 59 +++++++++++++++++++++++++++++++++++++-
>>  blockdev.c                 |  7 ++++-
>>  include/block/accounting.h |  5 +++-
>>  slirp                      |  2 +-
>>  4 files changed, 69 insertions(+), 4 deletions(-)
>>
> ...
>
>>  typedef struct BlockAcctCookie {
>> @@ -101,7 +104,7 @@ typedef struct BlockAcctCookie {
>>  
>>  void block_acct_init(BlockAcctStats *stats);
>>  void block_acct_setup(BlockAcctStats *stats, bool account_invalid,
>> -                     bool account_failed);
>> +                      bool account_failed, unsigned latency_log_threshold_ms);
>>  void block_acct_cleanup(BlockAcctStats *stats);
>>  void block_acct_add_interval(BlockAcctStats *stats, unsigned interval_length);
>>  BlockAcctTimedStats *block_acct_interval_next(BlockAcctStats *stats,
>> diff --git a/slirp b/slirp
>> index ce94eba204..2faae0f778 160000
>> --- a/slirp
>> +++ b/slirp
>> @@ -1 +1 @@
>> -Subproject commit ce94eba2042d52a0ba3d9e252ebce86715e94275
>> +Subproject commit 2faae0f778f818fadc873308f983289df697eb93
> SLiRP change unrelated I presume...
>
yes :(

subprojects comes into play.. I have not event changed this.
Just a result from pull :((((

Re: [PATCH 3/3] block: enable long IO requests report by default

[Max Reitz]

[-- Attachment #1.1: Type: text/plain, Size: 1322 bytes --]

On 10.08.20 12:14, Denis V. Lunev wrote:
> Latency threshold is set to 10 seconds following guest request timeout
> on legacy storage controller.
> 
> Signed-off-by: Denis V. Lunev <den@openvz.org>
> CC: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
> CC: Stefan Hajnoczi <stefanha@redhat.com>
> CC: Kevin Wolf <kwolf@redhat.com>
> CC: Max Reitz <mreitz@redhat.com>
> ---
>  blockdev.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/blockdev.c b/blockdev.c
> index 66158d1292..733fdd36da 100644
> --- a/blockdev.c
> +++ b/blockdev.c
> @@ -622,8 +622,13 @@ static BlockBackend *blockdev_init(const char *file, QDict *bs_opts,
>  
>          bs->detect_zeroes = detect_zeroes;
>  
> +        /*
> +         * Set log threshold to 10 seconds. Timeout choosen by observation

*chosen

> +         * of the guest behavior with legacy storage controllers. Linux
> +         * could remount FS read-only if journal write takes this time.
> +         */
>          block_acct_setup(blk_get_stats(blk), account_invalid, account_failed,
> -                qemu_opt_get_number(opts, "latency-log-threshold", 0));
> +                qemu_opt_get_number(opts, "latency-log-threshold", 10000));

Yeah, why not.

Reviewed-by: Max Reitz <mreitz@redhat.com>


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[PATCH 3/3] block: enable long IO requests report by default

[Denis V. Lunev]

Latency threshold is set to 10 seconds following guest request timeout
on legacy storage controller.

Signed-off-by: Denis V. Lunev <den@openvz.org>
CC: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
CC: Stefan Hajnoczi <stefanha@redhat.com>
CC: Kevin Wolf <kwolf@redhat.com>
CC: Max Reitz <mreitz@redhat.com>
---
 blockdev.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/blockdev.c b/blockdev.c
index 66158d1292..733fdd36da 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -622,8 +622,13 @@ static BlockBackend *blockdev_init(const char *file, QDict *bs_opts,
 
         bs->detect_zeroes = detect_zeroes;
 
+        /*
+         * Set log threshold to 10 seconds. Timeout choosen by observation
+         * of the guest behavior with legacy storage controllers. Linux
+         * could remount FS read-only if journal write takes this time.
+         */
         block_acct_setup(blk_get_stats(blk), account_invalid, account_failed,
-                qemu_opt_get_number(opts, "latency-log-threshold", 0));
+                qemu_opt_get_number(opts, "latency-log-threshold", 10000));
 
         if (!parse_stats_intervals(blk_get_stats(blk), interval_list, errp)) {
             blk_unref(blk);
-- 
2.17.1