From: Stefan Hajnoczi <stefanha@redhat.com>
To: Hanna Czenczek <hreitz@redhat.com>
Cc: qemu-block@nongnu.org, qemu-devel@nongnu.org,
Kevin Wolf <kwolf@redhat.com>, John Snow <jsnow@redhat.com>,
"Denis V . Lunev" <den@openvz.org>,
Eric Blake <eblake@redhat.com>,
Markus Armbruster <armbru@redhat.com>
Subject: Re: [PATCH 7/9] block: Add delay-alert-ms property
Date: Thu, 3 Sep 2026 10:30:56 -0400 [thread overview]
Message-ID: <20260903143055.GE825275@fedora> (raw)
In-Reply-To: <20260831135206.126184-8-hreitz@redhat.com>
[-- Attachment #1: Type: text/plain, Size: 20093 bytes --]
On Mon, Aug 31, 2026 at 03:52:03PM +0200, Hanna Czenczek wrote:
> This device property allows setting up an I/O latency threshold for when
> to emit a delay QMP event.
>
> Signed-off-by: Hanna Czenczek <hreitz@redhat.com>
> ---
> include/hw/block/block.h | 5 ++++-
> blockdev.c | 16 +++++++++++++++-
> hw/block/block.c | 4 +++-
> tests/qemu-iotests/172.out | 38 ++++++++++++++++++++++++++++++++++++++
> 4 files changed, 60 insertions(+), 3 deletions(-)
>
> diff --git a/include/hw/block/block.h b/include/hw/block/block.h
> index df941df19f2..e7e401dd303 100644
> --- a/include/hw/block/block.h
> +++ b/include/hw/block/block.h
> @@ -36,6 +36,7 @@ typedef struct BlockConf {
> BlockdevOnError werror;
> uint32_t num_stats_intervals;
> uint32_t *stats_intervals;
> + uint32_t delay_alert_ms;
> } BlockConf;
>
> static inline unsigned int get_physical_block_exp(BlockConf *conf)
> @@ -83,7 +84,9 @@ static inline unsigned int get_physical_block_exp(BlockConf *conf)
> _conf.account_failed, ON_OFF_AUTO_AUTO), \
> DEFINE_PROP_ARRAY("stats-intervals", _state, \
> _conf.num_stats_intervals, _conf.stats_intervals, \
> - qdev_prop_uint32, uint32_t)
> + qdev_prop_uint32, uint32_t), \
> + DEFINE_PROP_UINT32("delay-alert-ms", _state, _conf.delay_alert_ms, \
> + 0) \
The latency histogram feature uses nanoseconds (64-bit integer) whereas
this patch series uses delay-alert-ms (uint32) and a double
floating-point seconds value in the QMP event. Maybe stick to 64-bit
integer nanoseconds everywhere for consistency?
>
> #define DEFINE_BLOCK_PROPERTIES(_state, _conf) \
> DEFINE_PROP_DRIVE("drive", _state, _conf.blk), \
> diff --git a/blockdev.c b/blockdev.c
> index 195bac8af01..9c76e89ef38 100644
> --- a/blockdev.c
> +++ b/blockdev.c
> @@ -496,6 +496,7 @@ static BlockBackend *blockdev_init(const char *file, QDict *bs_opts,
> BlockdevDetectZeroesOptions detect_zeroes =
> BLOCKDEV_DETECT_ZEROES_OPTIONS_OFF;
> const char *throttling_group = NULL;
> + uint64_t delay_alert_ns;
>
> /* Check common options by copying from bs_opts to opts, all other options
> * stay in bs_opts for processing by bdrv_open(). */
> @@ -580,6 +581,14 @@ static BlockBackend *blockdev_init(const char *file, QDict *bs_opts,
>
> read_only = qemu_opt_get_bool(opts, BDRV_OPT_READ_ONLY, false);
>
> + delay_alert_ns = qemu_opt_get_number(opts, "delay-alert-ms", 0);
> + if (delay_alert_ns > (uint64_t)INT64_MAX / SCALE_MS) {
> + error_setg(errp, "delay-alert-ms must not exceed %" PRId64,
> + INT64_MAX / SCALE_MS);
> + goto early_err;
> + }
> + delay_alert_ns *= SCALE_MS;
> +
> /* init */
> if ((!file || !*file) && !qdict_size(bs_opts)) {
> BlockBackendRootState *blk_rs;
> @@ -618,7 +627,7 @@ 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,
> - NULL, 0, 0, NULL);
> + NULL, 0, delay_alert_ns, NULL);
>
> if (!parse_stats_intervals(blk_get_stats(blk), interval_list, errp)) {
> blk_unref(blk);
> @@ -3753,6 +3762,11 @@ QemuOptsList qemu_common_drive_opts = {
> .type = QEMU_OPT_BOOL,
> .help = "whether to account for failed I/O operations "
> "in the statistics",
> + },{
> + .name = "delay-alert-ms",
> + .type = QEMU_OPT_NUMBER,
> + .help = "threshold in ms when to emit an I/O operation "
> + "delay QMP event",
> },
> { /* end of list */ }
> },
> diff --git a/hw/block/block.c b/hw/block/block.c
> index 19301c6f995..be0ea89cb79 100644
> --- a/hw/block/block.c
> +++ b/hw/block/block.c
> @@ -207,6 +207,7 @@ bool blkconf_apply_backend_options(BlockConf *conf, bool readonly,
> BlockBackend *blk = conf->blk;
> BlockdevOnError rerror, werror;
> uint64_t perm, shared_perm;
> + uint64_t delay_alert_ns;
> bool wce;
> int ret;
>
> @@ -249,9 +250,10 @@ bool blkconf_apply_backend_options(BlockConf *conf, bool readonly,
> blk_set_enable_write_cache(blk, wce);
> blk_set_on_error(blk, rerror, werror);
>
> + delay_alert_ns = (uint64_t)conf->delay_alert_ms * SCALE_MS;
> if (!block_acct_setup(blk_get_stats(blk), conf->account_invalid,
> conf->account_failed, conf->stats_intervals,
> - conf->num_stats_intervals, 0, errp)) {
> + conf->num_stats_intervals, delay_alert_ns, errp)) {
> return false;
> }
> return true;
> diff --git a/tests/qemu-iotests/172.out b/tests/qemu-iotests/172.out
> index a023cd407de..ea6a1875eb3 100644
> --- a/tests/qemu-iotests/172.out
> +++ b/tests/qemu-iotests/172.out
> @@ -31,6 +31,7 @@ Testing:
> account-invalid = "auto"
> account-failed = "auto"
> stats-intervals = <null>
> + delay-alert-ms = 0 (0x0)
> drive-type = "288"
>
>
> @@ -61,6 +62,7 @@ Testing: -fda TEST_DIR/t.qcow2
> account-invalid = "auto"
> account-failed = "auto"
> stats-intervals = <null>
> + delay-alert-ms = 0 (0x0)
> drive-type = "144"
> floppy0 (NODE_NAME): TEST_DIR/t.qcow2 (qcow2)
> Attached to: /machine/unattached/device[N]
> @@ -98,6 +100,7 @@ Testing: -fdb TEST_DIR/t.qcow2
> account-invalid = "auto"
> account-failed = "auto"
> stats-intervals = <null>
> + delay-alert-ms = 0 (0x0)
> drive-type = "144"
> dev: floppy, id ""
> unit = 0 (0x0)
> @@ -113,6 +116,7 @@ Testing: -fdb TEST_DIR/t.qcow2
> account-invalid = "auto"
> account-failed = "auto"
> stats-intervals = <null>
> + delay-alert-ms = 0 (0x0)
> drive-type = "288"
> floppy1 (NODE_NAME): TEST_DIR/t.qcow2 (qcow2)
> Attached to: /machine/unattached/device[N]
> @@ -154,6 +158,7 @@ Testing: -fda TEST_DIR/t.qcow2 -fdb TEST_DIR/t.qcow2.2
> account-invalid = "auto"
> account-failed = "auto"
> stats-intervals = <null>
> + delay-alert-ms = 0 (0x0)
> drive-type = "144"
> dev: floppy, id ""
> unit = 0 (0x0)
> @@ -169,6 +174,7 @@ Testing: -fda TEST_DIR/t.qcow2 -fdb TEST_DIR/t.qcow2.2
> account-invalid = "auto"
> account-failed = "auto"
> stats-intervals = <null>
> + delay-alert-ms = 0 (0x0)
> drive-type = "144"
> floppy0 (NODE_NAME): TEST_DIR/t.qcow2 (qcow2)
> Attached to: /machine/unattached/device[N]
> @@ -211,6 +217,7 @@ Testing: -fdb
> account-invalid = "auto"
> account-failed = "auto"
> stats-intervals = <null>
> + delay-alert-ms = 0 (0x0)
> drive-type = "288"
> dev: floppy, id ""
> unit = 0 (0x0)
> @@ -226,6 +233,7 @@ Testing: -fdb
> account-invalid = "auto"
> account-failed = "auto"
> stats-intervals = <null>
> + delay-alert-ms = 0 (0x0)
> drive-type = "288"
>
>
> @@ -256,6 +264,7 @@ Testing: -drive if=floppy,file=TEST_DIR/t.qcow2
> account-invalid = "auto"
> account-failed = "auto"
> stats-intervals = <null>
> + delay-alert-ms = 0 (0x0)
> drive-type = "144"
> floppy0 (NODE_NAME): TEST_DIR/t.qcow2 (qcow2)
> Attached to: /machine/unattached/device[N]
> @@ -293,6 +302,7 @@ Testing: -drive if=floppy,file=TEST_DIR/t.qcow2,index=1
> account-invalid = "auto"
> account-failed = "auto"
> stats-intervals = <null>
> + delay-alert-ms = 0 (0x0)
> drive-type = "144"
> dev: floppy, id ""
> unit = 0 (0x0)
> @@ -308,6 +318,7 @@ Testing: -drive if=floppy,file=TEST_DIR/t.qcow2,index=1
> account-invalid = "auto"
> account-failed = "auto"
> stats-intervals = <null>
> + delay-alert-ms = 0 (0x0)
> drive-type = "288"
> floppy1 (NODE_NAME): TEST_DIR/t.qcow2 (qcow2)
> Attached to: /machine/unattached/device[N]
> @@ -349,6 +360,7 @@ Testing: -drive if=floppy,file=TEST_DIR/t.qcow2 -drive if=floppy,file=TEST_DIR/t
> account-invalid = "auto"
> account-failed = "auto"
> stats-intervals = <null>
> + delay-alert-ms = 0 (0x0)
> drive-type = "144"
> dev: floppy, id ""
> unit = 0 (0x0)
> @@ -364,6 +376,7 @@ Testing: -drive if=floppy,file=TEST_DIR/t.qcow2 -drive if=floppy,file=TEST_DIR/t
> account-invalid = "auto"
> account-failed = "auto"
> stats-intervals = <null>
> + delay-alert-ms = 0 (0x0)
> drive-type = "144"
> floppy0 (NODE_NAME): TEST_DIR/t.qcow2 (qcow2)
> Attached to: /machine/unattached/device[N]
> @@ -409,6 +422,7 @@ Testing: -drive if=none,file=TEST_DIR/t.qcow2 -device floppy,drive=none0
> account-invalid = "auto"
> account-failed = "auto"
> stats-intervals = <null>
> + delay-alert-ms = 0 (0x0)
> drive-type = "144"
> none0 (NODE_NAME): TEST_DIR/t.qcow2 (qcow2)
> Attached to: /machine/peripheral-anon/device[N]
> @@ -446,6 +460,7 @@ Testing: -drive if=none,file=TEST_DIR/t.qcow2 -device floppy,drive=none0,unit=1
> account-invalid = "auto"
> account-failed = "auto"
> stats-intervals = <null>
> + delay-alert-ms = 0 (0x0)
> drive-type = "144"
> none0 (NODE_NAME): TEST_DIR/t.qcow2 (qcow2)
> Attached to: /machine/peripheral-anon/device[N]
> @@ -483,6 +498,7 @@ Testing: -drive if=none,file=TEST_DIR/t.qcow2 -drive if=none,file=TEST_DIR/t.qco
> account-invalid = "auto"
> account-failed = "auto"
> stats-intervals = <null>
> + delay-alert-ms = 0 (0x0)
> drive-type = "144"
> dev: floppy, id ""
> unit = 0 (0x0)
> @@ -498,6 +514,7 @@ Testing: -drive if=none,file=TEST_DIR/t.qcow2 -drive if=none,file=TEST_DIR/t.qco
> account-invalid = "auto"
> account-failed = "auto"
> stats-intervals = <null>
> + delay-alert-ms = 0 (0x0)
> drive-type = "144"
> none0 (NODE_NAME): TEST_DIR/t.qcow2 (qcow2)
> Attached to: /machine/peripheral-anon/device[N]
> @@ -549,6 +566,7 @@ Testing: -fda TEST_DIR/t.qcow2 -drive if=none,file=TEST_DIR/t.qcow2.2 -device fl
> account-invalid = "auto"
> account-failed = "auto"
> stats-intervals = <null>
> + delay-alert-ms = 0 (0x0)
> drive-type = "144"
> dev: floppy, id ""
> unit = 0 (0x0)
> @@ -564,6 +582,7 @@ Testing: -fda TEST_DIR/t.qcow2 -drive if=none,file=TEST_DIR/t.qcow2.2 -device fl
> account-invalid = "auto"
> account-failed = "auto"
> stats-intervals = <null>
> + delay-alert-ms = 0 (0x0)
> drive-type = "144"
> floppy0 (NODE_NAME): TEST_DIR/t.qcow2 (qcow2)
> Attached to: /machine/unattached/device[N]
> @@ -606,6 +625,7 @@ Testing: -fda TEST_DIR/t.qcow2 -drive if=none,file=TEST_DIR/t.qcow2.2 -device fl
> account-invalid = "auto"
> account-failed = "auto"
> stats-intervals = <null>
> + delay-alert-ms = 0 (0x0)
> drive-type = "144"
> dev: floppy, id ""
> unit = 0 (0x0)
> @@ -621,6 +641,7 @@ Testing: -fda TEST_DIR/t.qcow2 -drive if=none,file=TEST_DIR/t.qcow2.2 -device fl
> account-invalid = "auto"
> account-failed = "auto"
> stats-intervals = <null>
> + delay-alert-ms = 0 (0x0)
> drive-type = "144"
> floppy0 (NODE_NAME): TEST_DIR/t.qcow2 (qcow2)
> Attached to: /machine/unattached/device[N]
> @@ -663,6 +684,7 @@ Testing: -fdb TEST_DIR/t.qcow2 -drive if=none,file=TEST_DIR/t.qcow2.2 -device fl
> account-invalid = "auto"
> account-failed = "auto"
> stats-intervals = <null>
> + delay-alert-ms = 0 (0x0)
> drive-type = "144"
> dev: floppy, id ""
> unit = 1 (0x1)
> @@ -678,6 +700,7 @@ Testing: -fdb TEST_DIR/t.qcow2 -drive if=none,file=TEST_DIR/t.qcow2.2 -device fl
> account-invalid = "auto"
> account-failed = "auto"
> stats-intervals = <null>
> + delay-alert-ms = 0 (0x0)
> drive-type = "144"
> floppy1 (NODE_NAME): TEST_DIR/t.qcow2 (qcow2)
> Attached to: /machine/unattached/device[N]
> @@ -720,6 +743,7 @@ Testing: -fdb TEST_DIR/t.qcow2 -drive if=none,file=TEST_DIR/t.qcow2.2 -device fl
> account-invalid = "auto"
> account-failed = "auto"
> stats-intervals = <null>
> + delay-alert-ms = 0 (0x0)
> drive-type = "144"
> dev: floppy, id ""
> unit = 1 (0x1)
> @@ -735,6 +759,7 @@ Testing: -fdb TEST_DIR/t.qcow2 -drive if=none,file=TEST_DIR/t.qcow2.2 -device fl
> account-invalid = "auto"
> account-failed = "auto"
> stats-intervals = <null>
> + delay-alert-ms = 0 (0x0)
> drive-type = "144"
> floppy1 (NODE_NAME): TEST_DIR/t.qcow2 (qcow2)
> Attached to: /machine/unattached/device[N]
> @@ -786,6 +811,7 @@ Testing: -drive if=floppy,file=TEST_DIR/t.qcow2 -drive if=none,file=TEST_DIR/t.q
> account-invalid = "auto"
> account-failed = "auto"
> stats-intervals = <null>
> + delay-alert-ms = 0 (0x0)
> drive-type = "144"
> dev: floppy, id ""
> unit = 0 (0x0)
> @@ -801,6 +827,7 @@ Testing: -drive if=floppy,file=TEST_DIR/t.qcow2 -drive if=none,file=TEST_DIR/t.q
> account-invalid = "auto"
> account-failed = "auto"
> stats-intervals = <null>
> + delay-alert-ms = 0 (0x0)
> drive-type = "144"
> floppy0 (NODE_NAME): TEST_DIR/t.qcow2 (qcow2)
> Attached to: /machine/unattached/device[N]
> @@ -843,6 +870,7 @@ Testing: -drive if=floppy,file=TEST_DIR/t.qcow2 -drive if=none,file=TEST_DIR/t.q
> account-invalid = "auto"
> account-failed = "auto"
> stats-intervals = <null>
> + delay-alert-ms = 0 (0x0)
> drive-type = "144"
> dev: floppy, id ""
> unit = 0 (0x0)
> @@ -858,6 +886,7 @@ Testing: -drive if=floppy,file=TEST_DIR/t.qcow2 -drive if=none,file=TEST_DIR/t.q
> account-invalid = "auto"
> account-failed = "auto"
> stats-intervals = <null>
> + delay-alert-ms = 0 (0x0)
> drive-type = "144"
> floppy0 (NODE_NAME): TEST_DIR/t.qcow2 (qcow2)
> Attached to: /machine/unattached/device[N]
> @@ -906,6 +935,7 @@ Testing: -drive if=none,file=TEST_DIR/t.qcow2 -global floppy.drive=none0 -device
> account-invalid = "auto"
> account-failed = "auto"
> stats-intervals = <null>
> + delay-alert-ms = 0 (0x0)
> drive-type = "144"
> none0 (NODE_NAME): TEST_DIR/t.qcow2 (qcow2)
> Attached to: /machine/peripheral-anon/device[N]
> @@ -973,6 +1003,7 @@ Testing: -device floppy
> account-invalid = "auto"
> account-failed = "auto"
> stats-intervals = <null>
> + delay-alert-ms = 0 (0x0)
> drive-type = "288"
>
> Testing: -device floppy,drive-type=120
> @@ -1000,6 +1031,7 @@ Testing: -device floppy,drive-type=120
> account-invalid = "auto"
> account-failed = "auto"
> stats-intervals = <null>
> + delay-alert-ms = 0 (0x0)
> drive-type = "120"
>
> Testing: -device floppy,drive-type=144
> @@ -1027,6 +1059,7 @@ Testing: -device floppy,drive-type=144
> account-invalid = "auto"
> account-failed = "auto"
> stats-intervals = <null>
> + delay-alert-ms = 0 (0x0)
> drive-type = "144"
>
> Testing: -device floppy,drive-type=288
> @@ -1054,6 +1087,7 @@ Testing: -device floppy,drive-type=288
> account-invalid = "auto"
> account-failed = "auto"
> stats-intervals = <null>
> + delay-alert-ms = 0 (0x0)
> drive-type = "288"
>
>
> @@ -1084,6 +1118,7 @@ Testing: -drive if=none,file=TEST_DIR/t.qcow2 -device floppy,drive=none0,drive-t
> account-invalid = "auto"
> account-failed = "auto"
> stats-intervals = <null>
> + delay-alert-ms = 0 (0x0)
> drive-type = "120"
> none0 (NODE_NAME): TEST_DIR/t.qcow2 (qcow2)
> Attached to: /machine/peripheral-anon/device[N]
> @@ -1121,6 +1156,7 @@ Testing: -drive if=none,file=TEST_DIR/t.qcow2 -device floppy,drive=none0,drive-t
> account-invalid = "auto"
> account-failed = "auto"
> stats-intervals = <null>
> + delay-alert-ms = 0 (0x0)
> drive-type = "288"
> none0 (NODE_NAME): TEST_DIR/t.qcow2 (qcow2)
> Attached to: /machine/peripheral-anon/device[N]
> @@ -1161,6 +1197,7 @@ Testing: -drive if=none,file=TEST_DIR/t.qcow2 -device floppy,drive=none0,logical
> account-invalid = "auto"
> account-failed = "auto"
> stats-intervals = <null>
> + delay-alert-ms = 0 (0x0)
> drive-type = "144"
> none0 (NODE_NAME): TEST_DIR/t.qcow2 (qcow2)
> Attached to: /machine/peripheral-anon/device[N]
> @@ -1198,6 +1235,7 @@ Testing: -drive if=none,file=TEST_DIR/t.qcow2 -device floppy,drive=none0,physica
> account-invalid = "auto"
> account-failed = "auto"
> stats-intervals = <null>
> + delay-alert-ms = 0 (0x0)
> drive-type = "144"
> none0 (NODE_NAME): TEST_DIR/t.qcow2 (qcow2)
> Attached to: /machine/peripheral-anon/device[N]
> --
> 2.55.0
>
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next prev parent reply other threads:[~2026-09-03 14:32 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-08-31 13:51 [PATCH 0/9] block: BLOCK_IO_DELAY event Hanna Czenczek
2026-08-31 13:51 ` [PATCH 1/9] block/accounting: Add offset to BlockAcctCookie Hanna Czenczek
2026-09-07 10:05 ` Jesper Wendel Devantier
2026-08-31 13:51 ` [PATCH 2/9] qapi/block: Add IoAccountingOperation enum Hanna Czenczek
2026-09-03 14:32 ` Markus Armbruster
2026-08-31 13:51 ` [PATCH 3/9] qapi/block: Add BLOCK_IO_DELAY event Hanna Czenczek
2026-09-03 14:36 ` Markus Armbruster
2026-08-31 13:52 ` [PATCH 4/9] block-backend: Public blk_get_attached_dev_path() Hanna Czenczek
2026-08-31 13:52 ` [PATCH 5/9] block/accounting: Add BB field to latency checker Hanna Czenczek
2026-08-31 13:52 ` [PATCH 6/9] block/accounting: Emit BLOCK_IO_DELAY event Hanna Czenczek
2026-09-03 14:23 ` Stefan Hajnoczi
2026-08-31 13:52 ` [PATCH 7/9] block: Add delay-alert-ms property Hanna Czenczek
2026-09-03 14:30 ` Stefan Hajnoczi [this message]
2026-08-31 13:52 ` [PATCH 8/9] block/accounting: Move latency_ns override down Hanna Czenczek
2026-09-03 15:08 ` Stefan Hajnoczi
2026-08-31 13:52 ` [PATCH 9/9] iotests: Add delay-alert test Hanna Czenczek
2026-09-03 15:16 ` Stefan Hajnoczi
2026-09-03 14:08 ` [PATCH 0/9] block: BLOCK_IO_DELAY event Stefan Hajnoczi
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