* [Qemu-devel] [PATCH v2 1/3] block/null: Latency simulation by adding new option "latency-ns"
2015-04-01 1:45 [Qemu-devel] [PATCH v2 0/3] null driver patches Fam Zheng
@ 2015-04-01 1:45 ` Fam Zheng
2015-04-01 1:45 ` [Qemu-devel] [PATCH v2 2/3] block/null: Support reopen Fam Zheng
` (3 subsequent siblings)
4 siblings, 0 replies; 6+ messages in thread
From: Fam Zheng @ 2015-04-01 1:45 UTC (permalink / raw)
To: qemu-devel; +Cc: Kevin Wolf, qemu-block, Stefan Hajnoczi
Aio context switch should just work because the requests will be
drained, so the scheduled timer(s) on the old context will be freed.
Signed-off-by: Fam Zheng <famz@redhat.com>
---
block/null.c | 58 ++++++++++++++++++++++++++++++++++++++++++++++------
qapi/block-core.json | 5 ++++-
2 files changed, 56 insertions(+), 7 deletions(-)
diff --git a/block/null.c b/block/null.c
index ec2bd27..267d3e6 100644
--- a/block/null.c
+++ b/block/null.c
@@ -12,8 +12,11 @@
#include "block/block_int.h"
+#define NULL_OPT_LATENCY "latency-ns"
+
typedef struct {
int64_t length;
+ int64_t latency_ns;
} BDRVNullState;
static QemuOptsList runtime_opts = {
@@ -30,6 +33,12 @@ static QemuOptsList runtime_opts = {
.type = QEMU_OPT_SIZE,
.help = "size of the null block",
},
+ {
+ .name = NULL_OPT_LATENCY,
+ .type = QEMU_OPT_NUMBER,
+ .help = "nanoseconds (approximated) to wait "
+ "before completing request",
+ },
{ /* end of list */ }
},
};
@@ -39,13 +48,20 @@ static int null_file_open(BlockDriverState *bs, QDict *options, int flags,
{
QemuOpts *opts;
BDRVNullState *s = bs->opaque;
+ int ret = 0;
opts = qemu_opts_create(&runtime_opts, NULL, 0, &error_abort);
qemu_opts_absorb_qdict(opts, options, &error_abort);
s->length =
qemu_opt_get_size(opts, BLOCK_OPT_SIZE, 1 << 30);
+ s->latency_ns =
+ qemu_opt_get_number(opts, NULL_OPT_LATENCY, 0);
+ if (s->latency_ns < 0) {
+ error_setg(errp, "latency-ns is invalid");
+ ret = -EINVAL;
+ }
qemu_opts_del(opts);
- return 0;
+ return ret;
}
static void null_close(BlockDriverState *bs)
@@ -58,28 +74,40 @@ static int64_t null_getlength(BlockDriverState *bs)
return s->length;
}
+static coroutine_fn int null_co_common(BlockDriverState *bs)
+{
+ BDRVNullState *s = bs->opaque;
+
+ if (s->latency_ns) {
+ co_aio_sleep_ns(bdrv_get_aio_context(bs), QEMU_CLOCK_REALTIME,
+ s->latency_ns);
+ }
+ return 0;
+}
+
static coroutine_fn int null_co_readv(BlockDriverState *bs,
int64_t sector_num, int nb_sectors,
QEMUIOVector *qiov)
{
- return 0;
+ return null_co_common(bs);
}
static coroutine_fn int null_co_writev(BlockDriverState *bs,
int64_t sector_num, int nb_sectors,
QEMUIOVector *qiov)
{
- return 0;
+ return null_co_common(bs);
}
static coroutine_fn int null_co_flush(BlockDriverState *bs)
{
- return 0;
+ return null_co_common(bs);
}
typedef struct {
BlockAIOCB common;
QEMUBH *bh;
+ QEMUTimer timer;
} NullAIOCB;
static const AIOCBInfo null_aiocb_info = {
@@ -94,15 +122,33 @@ static void null_bh_cb(void *opaque)
qemu_aio_unref(acb);
}
+static void null_timer_cb(void *opaque)
+{
+ NullAIOCB *acb = opaque;
+ acb->common.cb(acb->common.opaque, 0);
+ timer_deinit(&acb->timer);
+ qemu_aio_unref(acb);
+}
+
static inline BlockAIOCB *null_aio_common(BlockDriverState *bs,
BlockCompletionFunc *cb,
void *opaque)
{
NullAIOCB *acb;
+ BDRVNullState *s = bs->opaque;
acb = qemu_aio_get(&null_aiocb_info, bs, cb, opaque);
- acb->bh = aio_bh_new(bdrv_get_aio_context(bs), null_bh_cb, acb);
- qemu_bh_schedule(acb->bh);
+ /* Only emulate latency after vcpu is running. */
+ if (s->latency_ns) {
+ aio_timer_init(bdrv_get_aio_context(bs), &acb->timer,
+ QEMU_CLOCK_REALTIME, SCALE_NS,
+ null_timer_cb, acb);
+ timer_mod_ns(&acb->timer,
+ qemu_clock_get_ns(QEMU_CLOCK_REALTIME) + s->latency_ns);
+ } else {
+ acb->bh = aio_bh_new(bdrv_get_aio_context(bs), null_bh_cb, acb);
+ qemu_bh_schedule(acb->bh);
+ }
return &acb->common;
}
diff --git a/qapi/block-core.json b/qapi/block-core.json
index 7873084..e158a7c 100644
--- a/qapi/block-core.json
+++ b/qapi/block-core.json
@@ -1310,11 +1310,14 @@
# Driver specific block device options for the null backend.
#
# @size: #optional size of the device in bytes.
+# @latency-ns: #optional emulated latency (in nanoseconds) in processing
+# requests. Default to zero which completes requests immediately.
+# (Since 2.4)
#
# Since: 2.2
##
{ 'type': 'BlockdevOptionsNull',
- 'data': { '*size': 'int' } }
+ 'data': { '*size': 'int', '*latency-ns': 'uint64' } }
##
# @BlockdevOptionsVVFAT
--
1.9.3
^ permalink raw reply related [flat|nested] 6+ messages in thread* [Qemu-devel] [PATCH v2 2/3] block/null: Support reopen
2015-04-01 1:45 [Qemu-devel] [PATCH v2 0/3] null driver patches Fam Zheng
2015-04-01 1:45 ` [Qemu-devel] [PATCH v2 1/3] block/null: Latency simulation by adding new option "latency-ns" Fam Zheng
@ 2015-04-01 1:45 ` Fam Zheng
2015-04-01 1:45 ` [Qemu-devel] [PATCH v2 3/3] MAINTAINERS: Add Fam Zheng as Null block driver maintainer Fam Zheng
` (2 subsequent siblings)
4 siblings, 0 replies; 6+ messages in thread
From: Fam Zheng @ 2015-04-01 1:45 UTC (permalink / raw)
To: qemu-devel; +Cc: Kevin Wolf, qemu-block, Stefan Hajnoczi
Reopen is used in block-commit. With this always-succeed operation, it
is now possible to test committing to a null drive, by specifying
"null-aio://" or "null-co://" as the backing image when creating the
qcow2 image.
Signed-off-by: Fam Zheng <famz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
---
block/null.c | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/block/null.c b/block/null.c
index 267d3e6..7d08323 100644
--- a/block/null.c
+++ b/block/null.c
@@ -177,6 +177,12 @@ static BlockAIOCB *null_aio_flush(BlockDriverState *bs,
return null_aio_common(bs, cb, opaque);
}
+static int null_reopen_prepare(BDRVReopenState *reopen_state,
+ BlockReopenQueue *queue, Error **errp)
+{
+ return 0;
+}
+
static BlockDriver bdrv_null_co = {
.format_name = "null-co",
.protocol_name = "null-co",
@@ -189,6 +195,7 @@ static BlockDriver bdrv_null_co = {
.bdrv_co_readv = null_co_readv,
.bdrv_co_writev = null_co_writev,
.bdrv_co_flush_to_disk = null_co_flush,
+ .bdrv_reopen_prepare = null_reopen_prepare,
};
static BlockDriver bdrv_null_aio = {
@@ -203,6 +210,7 @@ static BlockDriver bdrv_null_aio = {
.bdrv_aio_readv = null_aio_readv,
.bdrv_aio_writev = null_aio_writev,
.bdrv_aio_flush = null_aio_flush,
+ .bdrv_reopen_prepare = null_reopen_prepare,
};
static void bdrv_null_init(void)
--
1.9.3
^ permalink raw reply related [flat|nested] 6+ messages in thread