* [Qemu-devel] [PULL 1/3] iov: avoid memcpy for "simple" iov_from_buf/iov_to_buf
2016-02-09 15:11 [Qemu-devel] [PULL 0/3] Block patches Stefan Hajnoczi
@ 2016-02-09 15:11 ` Stefan Hajnoczi
2016-02-09 15:11 ` [Qemu-devel] [PULL 2/3] blockjob: Fix hang in block_job_finish_sync Stefan Hajnoczi
` (2 subsequent siblings)
3 siblings, 0 replies; 5+ messages in thread
From: Stefan Hajnoczi @ 2016-02-09 15:11 UTC (permalink / raw)
To: qemu-devel; +Cc: Peter Maydell, Stefan Hajnoczi, Paolo Bonzini
From: Paolo Bonzini <pbonzini@redhat.com>
memcpy can take a large amount of time for small reads and writes.
For virtio it is a common case that the first iovec can satisfy the
whole read or write. In that case, and if bytes is a constant to
avoid excessive growth of code, inline the first iteration
into the caller.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-id: 1450782213-14227-1-git-send-email-pbonzini@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
include/qemu/iov.h | 34 ++++++++++++++++++++++++++++++----
util/iov.c | 8 ++++----
2 files changed, 34 insertions(+), 8 deletions(-)
diff --git a/include/qemu/iov.h b/include/qemu/iov.h
index 569b2c2..2847551 100644
--- a/include/qemu/iov.h
+++ b/include/qemu/iov.h
@@ -39,10 +39,36 @@ size_t iov_size(const struct iovec *iov, const unsigned int iov_cnt);
* such "large" value is -1 (sinice size_t is unsigned),
* so specifying `-1' as `bytes' means 'up to the end of iovec'.
*/
-size_t iov_from_buf(const struct iovec *iov, unsigned int iov_cnt,
- size_t offset, const void *buf, size_t bytes);
-size_t iov_to_buf(const struct iovec *iov, const unsigned int iov_cnt,
- size_t offset, void *buf, size_t bytes);
+size_t iov_from_buf_full(const struct iovec *iov, unsigned int iov_cnt,
+ size_t offset, const void *buf, size_t bytes);
+size_t iov_to_buf_full(const struct iovec *iov, const unsigned int iov_cnt,
+ size_t offset, void *buf, size_t bytes);
+
+static inline size_t
+iov_from_buf(const struct iovec *iov, unsigned int iov_cnt,
+ size_t offset, const void *buf, size_t bytes)
+{
+ if (__builtin_constant_p(bytes) && iov_cnt &&
+ offset <= iov[0].iov_len && bytes <= iov[0].iov_len - offset) {
+ memcpy(iov[0].iov_base + offset, buf, bytes);
+ return bytes;
+ } else {
+ return iov_from_buf_full(iov, iov_cnt, offset, buf, bytes);
+ }
+}
+
+static inline size_t
+iov_to_buf(const struct iovec *iov, const unsigned int iov_cnt,
+ size_t offset, void *buf, size_t bytes)
+{
+ if (__builtin_constant_p(bytes) && iov_cnt &&
+ offset <= iov[0].iov_len && bytes <= iov[0].iov_len - offset) {
+ memcpy(buf, iov[0].iov_base + offset, bytes);
+ return bytes;
+ } else {
+ return iov_to_buf_full(iov, iov_cnt, offset, buf, bytes);
+ }
+}
/**
* Set data bytes pointed out by iovec `iov' of size `iov_cnt' elements,
diff --git a/util/iov.c b/util/iov.c
index e802ee1..062f4e5 100644
--- a/util/iov.c
+++ b/util/iov.c
@@ -20,8 +20,8 @@
#include "qemu/iov.h"
#include "qemu/sockets.h"
-size_t iov_from_buf(const struct iovec *iov, unsigned int iov_cnt,
- size_t offset, const void *buf, size_t bytes)
+size_t iov_from_buf_full(const struct iovec *iov, unsigned int iov_cnt,
+ size_t offset, const void *buf, size_t bytes)
{
size_t done;
unsigned int i;
@@ -39,8 +39,8 @@ size_t iov_from_buf(const struct iovec *iov, unsigned int iov_cnt,
return done;
}
-size_t iov_to_buf(const struct iovec *iov, const unsigned int iov_cnt,
- size_t offset, void *buf, size_t bytes)
+size_t iov_to_buf_full(const struct iovec *iov, const unsigned int iov_cnt,
+ size_t offset, void *buf, size_t bytes)
{
size_t done;
unsigned int i;
--
2.5.0
^ permalink raw reply related [flat|nested] 5+ messages in thread* [Qemu-devel] [PULL 2/3] blockjob: Fix hang in block_job_finish_sync
2016-02-09 15:11 [Qemu-devel] [PULL 0/3] Block patches Stefan Hajnoczi
2016-02-09 15:11 ` [Qemu-devel] [PULL 1/3] iov: avoid memcpy for "simple" iov_from_buf/iov_to_buf Stefan Hajnoczi
@ 2016-02-09 15:11 ` Stefan Hajnoczi
2016-02-09 15:11 ` [Qemu-devel] [PULL 3/3] block: add missing call to bdrv_drain_recurse Stefan Hajnoczi
2016-02-09 19:34 ` [Qemu-devel] [PULL 0/3] Block patches Peter Maydell
3 siblings, 0 replies; 5+ messages in thread
From: Stefan Hajnoczi @ 2016-02-09 15:11 UTC (permalink / raw)
To: qemu-devel; +Cc: Peter Maydell, Fam Zheng, Stefan Hajnoczi
From: Fam Zheng <famz@redhat.com>
With a mirror job running on a virtio-blk dataplane disk, sending "q" to
HMP will cause a dead loop in block_job_finish_sync.
This is because the aio_poll() only processes the AIO context of bs
which has no more work to do, while the main loop BH that is scheduled
for setting the job->completed flag is never processed.
Fix this by adding a flag in BlockJob structure, to track which context
to poll for the block job to make progress. Its value is set to true
when block_job_coroutine_complete() is called, and is checked in
block_job_finish_sync to determine which context to poll.
Suggested-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Fam Zheng <famz@redhat.com>
Message-id: 1454379144-29807-1-git-send-email-famz@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
blockjob.c | 6 +++++-
include/block/blockjob.h | 5 +++++
2 files changed, 10 insertions(+), 1 deletion(-)
diff --git a/blockjob.c b/blockjob.c
index a402181..9fc37ca 100644
--- a/blockjob.c
+++ b/blockjob.c
@@ -296,7 +296,9 @@ static int block_job_finish_sync(BlockJob *job,
return -EBUSY;
}
while (!job->completed) {
- aio_poll(bdrv_get_aio_context(bs), true);
+ aio_poll(job->deferred_to_main_loop ? qemu_get_aio_context() :
+ bdrv_get_aio_context(bs),
+ true);
}
ret = (job->cancelled && job->ret == 0) ? -ECANCELED : job->ret;
block_job_unref(job);
@@ -470,6 +472,7 @@ static void block_job_defer_to_main_loop_bh(void *opaque)
aio_context = bdrv_get_aio_context(data->job->bs);
aio_context_acquire(aio_context);
+ data->job->deferred_to_main_loop = false;
data->fn(data->job, data->opaque);
aio_context_release(aio_context);
@@ -489,6 +492,7 @@ void block_job_defer_to_main_loop(BlockJob *job,
data->aio_context = bdrv_get_aio_context(job->bs);
data->fn = fn;
data->opaque = opaque;
+ job->deferred_to_main_loop = true;
qemu_bh_schedule(data->bh);
}
diff --git a/include/block/blockjob.h b/include/block/blockjob.h
index d84ccd8..8bedc49 100644
--- a/include/block/blockjob.h
+++ b/include/block/blockjob.h
@@ -130,6 +130,11 @@ struct BlockJob {
*/
bool ready;
+ /**
+ * Set to true when the job has deferred work to the main loop.
+ */
+ bool deferred_to_main_loop;
+
/** Status that is published by the query-block-jobs QMP API */
BlockDeviceIoStatus iostatus;
--
2.5.0
^ permalink raw reply related [flat|nested] 5+ messages in thread