* [Qemu-devel] [PATCH v3 for-4.2 0/3] block: BDRV_REQ_PREFETCH
@ 2019-07-25 10:05 Vladimir Sementsov-Ogievskiy
2019-07-25 10:05 ` [Qemu-devel] [PATCH v3 1/3] block: implement BDRV_REQ_PREFETCH Vladimir Sementsov-Ogievskiy
` (3 more replies)
0 siblings, 4 replies; 10+ messages in thread
From: Vladimir Sementsov-Ogievskiy @ 2019-07-25 10:05 UTC (permalink / raw)
To: qemu-devel, qemu-block
Cc: kwolf, fam, vsementsov, mreitz, stefanha, den, jsnow
Hi all!
Here is small new read flag: BDRV_REQ_PREFETCH, which in combination with
BDRV_REQ_COPY_ON_READ does copy-on-read without
extra buffer for read data. This means that only parts that needs COR
will be actually read and only corresponding buffers allocated, no more.
This allows to improve a bit block-stream and NBD_CMD_CACHE
v3: rebase 02 on master, fix commit message of 03.
v2: change interface to be just one flag BDRV_REQ_PREFETCH
v1 was "[PATCH 0/3] block: blk_co_pcache"
https://lists.gnu.org/archive/html/qemu-devel/2019-06/msg01047.html
Vladimir Sementsov-Ogievskiy (3):
block: implement BDRV_REQ_PREFETCH
block/stream: use BDRV_REQ_PREFETCH
nbd: improve CMD_CACHE: use BDRV_REQ_PREFETCH
include/block/block.h | 8 +++++++-
block/io.c | 18 ++++++++++++------
block/stream.c | 20 +++++++-------------
nbd/server.c | 43 +++++++++++++++++++++++++++++++++++--------
4 files changed, 61 insertions(+), 28 deletions(-)
--
2.18.0
^ permalink raw reply [flat|nested] 10+ messages in thread
* [Qemu-devel] [PATCH v3 1/3] block: implement BDRV_REQ_PREFETCH
2019-07-25 10:05 [Qemu-devel] [PATCH v3 for-4.2 0/3] block: BDRV_REQ_PREFETCH Vladimir Sementsov-Ogievskiy
@ 2019-07-25 10:05 ` Vladimir Sementsov-Ogievskiy
2019-07-29 21:13 ` Eric Blake
2019-07-25 10:05 ` [Qemu-devel] [PATCH v3 2/3] block/stream: use BDRV_REQ_PREFETCH Vladimir Sementsov-Ogievskiy
` (2 subsequent siblings)
3 siblings, 1 reply; 10+ messages in thread
From: Vladimir Sementsov-Ogievskiy @ 2019-07-25 10:05 UTC (permalink / raw)
To: qemu-devel, qemu-block
Cc: kwolf, fam, vsementsov, mreitz, stefanha, den, jsnow
Do effective copy-on-read request when we don't need data actually. It
will be used for block-stream and NBD_CMD_CACHE.
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
---
include/block/block.h | 8 +++++++-
block/io.c | 18 ++++++++++++------
2 files changed, 19 insertions(+), 7 deletions(-)
diff --git a/include/block/block.h b/include/block/block.h
index 50a07c1c33..73c3fc4daa 100644
--- a/include/block/block.h
+++ b/include/block/block.h
@@ -88,8 +88,14 @@ typedef enum {
* fallback. */
BDRV_REQ_NO_FALLBACK = 0x100,
+ /*
+ * BDRV_REQ_PREFETCH may be used only together with BDRV_REQ_COPY_ON_READ
+ * on read request and means that caller don't really need data to be
+ * written to qiov parameter which may be NULL.
+ */
+ BDRV_REQ_PREFETCH = 0x200,
/* Mask of valid flags */
- BDRV_REQ_MASK = 0x1ff,
+ BDRV_REQ_MASK = 0x3ff,
} BdrvRequestFlags;
typedef struct BlockSizes {
diff --git a/block/io.c b/block/io.c
index 06305c6ea6..9d99858b55 100644
--- a/block/io.c
+++ b/block/io.c
@@ -1167,7 +1167,8 @@ bdrv_driver_pwritev_compressed(BlockDriverState *bs, uint64_t offset,
}
static int coroutine_fn bdrv_co_do_copy_on_readv(BdrvChild *child,
- int64_t offset, unsigned int bytes, QEMUIOVector *qiov)
+ int64_t offset, unsigned int bytes, QEMUIOVector *qiov,
+ int flags)
{
BlockDriverState *bs = child->bs;
@@ -1278,9 +1279,11 @@ static int coroutine_fn bdrv_co_do_copy_on_readv(BdrvChild *child,
goto err;
}
- qemu_iovec_from_buf(qiov, progress, bounce_buffer + skip_bytes,
- pnum - skip_bytes);
- } else {
+ if (!(flags & BDRV_REQ_PREFETCH)) {
+ qemu_iovec_from_buf(qiov, progress, bounce_buffer + skip_bytes,
+ pnum - skip_bytes);
+ }
+ } else if (!(flags & BDRV_REQ_PREFETCH)) {
/* Read directly into the destination */
qemu_iovec_init(&local_qiov, qiov->niov);
qemu_iovec_concat(&local_qiov, qiov, progress, pnum - skip_bytes);
@@ -1331,7 +1334,8 @@ static int coroutine_fn bdrv_aligned_preadv(BdrvChild *child,
* potential fallback support, if we ever implement any read flags
* to pass through to drivers. For now, there aren't any
* passthrough flags. */
- assert(!(flags & ~(BDRV_REQ_NO_SERIALISING | BDRV_REQ_COPY_ON_READ)));
+ assert(!(flags & ~(BDRV_REQ_NO_SERIALISING | BDRV_REQ_COPY_ON_READ |
+ BDRV_REQ_PREFETCH)));
/* Handle Copy on Read and associated serialisation */
if (flags & BDRV_REQ_COPY_ON_READ) {
@@ -1359,7 +1363,9 @@ static int coroutine_fn bdrv_aligned_preadv(BdrvChild *child,
}
if (!ret || pnum != bytes) {
- ret = bdrv_co_do_copy_on_readv(child, offset, bytes, qiov);
+ ret = bdrv_co_do_copy_on_readv(child, offset, bytes, qiov, flags);
+ goto out;
+ } else if (flags & BDRV_REQ_PREFETCH) {
goto out;
}
}
--
2.18.0
^ permalink raw reply related [flat|nested] 10+ messages in thread
* [Qemu-devel] [PATCH v3 2/3] block/stream: use BDRV_REQ_PREFETCH
2019-07-25 10:05 [Qemu-devel] [PATCH v3 for-4.2 0/3] block: BDRV_REQ_PREFETCH Vladimir Sementsov-Ogievskiy
2019-07-25 10:05 ` [Qemu-devel] [PATCH v3 1/3] block: implement BDRV_REQ_PREFETCH Vladimir Sementsov-Ogievskiy
@ 2019-07-25 10:05 ` Vladimir Sementsov-Ogievskiy
2019-07-29 21:19 ` Eric Blake
2019-07-25 10:05 ` [Qemu-devel] [PATCH v3 3/3] nbd: improve CMD_CACHE: " Vladimir Sementsov-Ogievskiy
2019-07-29 15:00 ` [Qemu-devel] [Qemu-block] [PATCH v3 for-4.2 0/3] block: BDRV_REQ_PREFETCH Stefan Hajnoczi
3 siblings, 1 reply; 10+ messages in thread
From: Vladimir Sementsov-Ogievskiy @ 2019-07-25 10:05 UTC (permalink / raw)
To: qemu-devel, qemu-block
Cc: kwolf, fam, vsementsov, mreitz, stefanha, den, jsnow
This helps to avoid extra io, allocations and memory copying.
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
---
block/stream.c | 20 +++++++-------------
1 file changed, 7 insertions(+), 13 deletions(-)
diff --git a/block/stream.c b/block/stream.c
index 6ac1e7bec4..170e3b43be 100644
--- a/block/stream.c
+++ b/block/stream.c
@@ -22,11 +22,11 @@
enum {
/*
- * Size of data buffer for populating the image file. This should be large
+ * Maximum chunk size to feed it to copy-on-read. This should be large
* enough to process multiple clusters in a single call, so that populating
* contiguous regions of the image is efficient.
*/
- STREAM_BUFFER_SIZE = 512 * 1024, /* in bytes */
+ STREAM_CHUNK = 512 * 1024, /* in bytes */
};
typedef struct StreamBlockJob {
@@ -39,13 +39,12 @@ typedef struct StreamBlockJob {
} StreamBlockJob;
static int coroutine_fn stream_populate(BlockBackend *blk,
- int64_t offset, uint64_t bytes,
- void *buf)
+ int64_t offset, uint64_t bytes)
{
assert(bytes < SIZE_MAX);
- /* Copy-on-read the unallocated clusters */
- return blk_co_pread(blk, offset, bytes, buf, BDRV_REQ_COPY_ON_READ);
+ return blk_co_preadv(blk, offset, bytes, NULL,
+ BDRV_REQ_COPY_ON_READ | BDRV_REQ_PREFETCH);
}
static void stream_abort(Job *job)
@@ -117,7 +116,6 @@ static int coroutine_fn stream_run(Job *job, Error **errp)
int error = 0;
int ret = 0;
int64_t n = 0; /* bytes */
- void *buf;
if (bs == s->bottom) {
/* Nothing to stream */
@@ -130,8 +128,6 @@ static int coroutine_fn stream_run(Job *job, Error **errp)
}
job_progress_set_remaining(&s->common.job, len);
- buf = qemu_blockalign(bs, STREAM_BUFFER_SIZE);
-
/* Turn on copy-on-read for the whole block device so that guest read
* requests help us make progress. Only do this when copying the entire
* backing chain since the copy-on-read operation does not take base into
@@ -154,7 +150,7 @@ static int coroutine_fn stream_run(Job *job, Error **errp)
copy = false;
- ret = bdrv_is_allocated(bs, offset, STREAM_BUFFER_SIZE, &n);
+ ret = bdrv_is_allocated(bs, offset, STREAM_CHUNK, &n);
if (ret == 1) {
/* Allocated in the top, no need to copy. */
} else if (ret >= 0) {
@@ -171,7 +167,7 @@ static int coroutine_fn stream_run(Job *job, Error **errp)
}
trace_stream_one_iteration(s, offset, n, ret);
if (copy) {
- ret = stream_populate(blk, offset, n, buf);
+ ret = stream_populate(blk, offset, n);
}
if (ret < 0) {
BlockErrorAction action =
@@ -202,8 +198,6 @@ static int coroutine_fn stream_run(Job *job, Error **errp)
bdrv_disable_copy_on_read(bs);
}
- qemu_vfree(buf);
-
/* Do not remove the backing file if an error was there but ignored. */
return error;
}
--
2.18.0
^ permalink raw reply related [flat|nested] 10+ messages in thread
* [Qemu-devel] [PATCH v3 3/3] nbd: improve CMD_CACHE: use BDRV_REQ_PREFETCH
2019-07-25 10:05 [Qemu-devel] [PATCH v3 for-4.2 0/3] block: BDRV_REQ_PREFETCH Vladimir Sementsov-Ogievskiy
2019-07-25 10:05 ` [Qemu-devel] [PATCH v3 1/3] block: implement BDRV_REQ_PREFETCH Vladimir Sementsov-Ogievskiy
2019-07-25 10:05 ` [Qemu-devel] [PATCH v3 2/3] block/stream: use BDRV_REQ_PREFETCH Vladimir Sementsov-Ogievskiy
@ 2019-07-25 10:05 ` Vladimir Sementsov-Ogievskiy
2019-07-29 21:24 ` Eric Blake
2019-07-29 15:00 ` [Qemu-devel] [Qemu-block] [PATCH v3 for-4.2 0/3] block: BDRV_REQ_PREFETCH Stefan Hajnoczi
3 siblings, 1 reply; 10+ messages in thread
From: Vladimir Sementsov-Ogievskiy @ 2019-07-25 10:05 UTC (permalink / raw)
To: qemu-devel, qemu-block
Cc: kwolf, fam, vsementsov, mreitz, stefanha, den, jsnow
This helps to avoid extra io, allocations and memory copying.
We assume here that CMD_CACHE is always used with copy-on-read, as
otherwise it's a noop.
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
---
nbd/server.c | 43 +++++++++++++++++++++++++++++++++++--------
1 file changed, 35 insertions(+), 8 deletions(-)
diff --git a/nbd/server.c b/nbd/server.c
index 10faedcfc5..a2cf085f76 100644
--- a/nbd/server.c
+++ b/nbd/server.c
@@ -2104,12 +2104,15 @@ static int nbd_co_receive_request(NBDRequestData *req, NBDRequest *request,
return -EINVAL;
}
- req->data = blk_try_blockalign(client->exp->blk, request->len);
- if (req->data == NULL) {
- error_setg(errp, "No memory");
- return -ENOMEM;
+ if (request->type != NBD_CMD_CACHE) {
+ req->data = blk_try_blockalign(client->exp->blk, request->len);
+ if (req->data == NULL) {
+ error_setg(errp, "No memory");
+ return -ENOMEM;
+ }
}
}
+
if (request->type == NBD_CMD_WRITE) {
if (nbd_read(client->ioc, req->data, request->len, "CMD_WRITE data",
errp) < 0)
@@ -2194,7 +2197,7 @@ static coroutine_fn int nbd_do_cmd_read(NBDClient *client, NBDRequest *request,
int ret;
NBDExport *exp = client->exp;
- assert(request->type == NBD_CMD_READ || request->type == NBD_CMD_CACHE);
+ assert(request->type == NBD_CMD_READ);
/* XXX: NBD Protocol only documents use of FUA with WRITE */
if (request->flags & NBD_CMD_FLAG_FUA) {
@@ -2206,7 +2209,7 @@ static coroutine_fn int nbd_do_cmd_read(NBDClient *client, NBDRequest *request,
}
if (client->structured_reply && !(request->flags & NBD_CMD_FLAG_DF) &&
- request->len && request->type != NBD_CMD_CACHE)
+ request->len)
{
return nbd_co_send_sparse_read(client, request->handle, request->from,
data, request->len, errp);
@@ -2214,7 +2217,7 @@ static coroutine_fn int nbd_do_cmd_read(NBDClient *client, NBDRequest *request,
ret = blk_pread(exp->blk, request->from + exp->dev_offset, data,
request->len);
- if (ret < 0 || request->type == NBD_CMD_CACHE) {
+ if (ret < 0) {
return nbd_send_generic_reply(client, request->handle, ret,
"reading from file failed", errp);
}
@@ -2233,6 +2236,28 @@ static coroutine_fn int nbd_do_cmd_read(NBDClient *client, NBDRequest *request,
}
}
+/*
+ * nbd_do_cmd_cache
+ *
+ * Handle NBD_CMD_CACHE request.
+ * Return -errno if sending fails. Other errors are reported directly to the
+ * client as an error reply.
+ */
+static coroutine_fn int nbd_do_cmd_cache(NBDClient *client, NBDRequest *request,
+ Error **errp)
+{
+ int ret;
+ NBDExport *exp = client->exp;
+
+ assert(request->type == NBD_CMD_CACHE);
+
+ ret = blk_co_preadv(exp->blk, request->from + exp->dev_offset, request->len,
+ NULL, BDRV_REQ_COPY_ON_READ | BDRV_REQ_PREFETCH);
+
+ return nbd_send_generic_reply(client, request->handle, ret,
+ "caching data failed", errp);
+}
+
/* Handle NBD request.
* Return -errno if sending fails. Other errors are reported directly to the
* client as an error reply. */
@@ -2246,8 +2271,10 @@ static coroutine_fn int nbd_handle_request(NBDClient *client,
char *msg;
switch (request->type) {
- case NBD_CMD_READ:
case NBD_CMD_CACHE:
+ return nbd_do_cmd_cache(client, request, errp);
+
+ case NBD_CMD_READ:
return nbd_do_cmd_read(client, request, data, errp);
case NBD_CMD_WRITE:
--
2.18.0
^ permalink raw reply related [flat|nested] 10+ messages in thread
* Re: [Qemu-devel] [Qemu-block] [PATCH v3 for-4.2 0/3] block: BDRV_REQ_PREFETCH
2019-07-25 10:05 [Qemu-devel] [PATCH v3 for-4.2 0/3] block: BDRV_REQ_PREFETCH Vladimir Sementsov-Ogievskiy
` (2 preceding siblings ...)
2019-07-25 10:05 ` [Qemu-devel] [PATCH v3 3/3] nbd: improve CMD_CACHE: " Vladimir Sementsov-Ogievskiy
@ 2019-07-29 15:00 ` Stefan Hajnoczi
2019-07-29 15:29 ` Vladimir Sementsov-Ogievskiy
2019-07-29 15:38 ` Eric Blake
3 siblings, 2 replies; 10+ messages in thread
From: Stefan Hajnoczi @ 2019-07-29 15:00 UTC (permalink / raw)
To: Vladimir Sementsov-Ogievskiy
Cc: kwolf, fam, qemu-block, qemu-devel, mreitz, stefanha, den
[-- Attachment #1: Type: text/plain, Size: 1217 bytes --]
On Thu, Jul 25, 2019 at 01:05:47PM +0300, Vladimir Sementsov-Ogievskiy wrote:
> Hi all!
>
> Here is small new read flag: BDRV_REQ_PREFETCH, which in combination with
> BDRV_REQ_COPY_ON_READ does copy-on-read without
> extra buffer for read data. This means that only parts that needs COR
> will be actually read and only corresponding buffers allocated, no more.
>
> This allows to improve a bit block-stream and NBD_CMD_CACHE
>
> v3: rebase 02 on master, fix commit message of 03.
>
> v2: change interface to be just one flag BDRV_REQ_PREFETCH
>
> v1 was "[PATCH 0/3] block: blk_co_pcache"
> https://lists.gnu.org/archive/html/qemu-devel/2019-06/msg01047.html
>
> Vladimir Sementsov-Ogievskiy (3):
> block: implement BDRV_REQ_PREFETCH
> block/stream: use BDRV_REQ_PREFETCH
> nbd: improve CMD_CACHE: use BDRV_REQ_PREFETCH
>
> include/block/block.h | 8 +++++++-
> block/io.c | 18 ++++++++++++------
> block/stream.c | 20 +++++++-------------
> nbd/server.c | 43 +++++++++++++++++++++++++++++++++++--------
> 4 files changed, 61 insertions(+), 28 deletions(-)
>
> --
> 2.18.0
>
>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
[-- Attachment #2: signature.asc --]
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^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [Qemu-devel] [Qemu-block] [PATCH v3 for-4.2 0/3] block: BDRV_REQ_PREFETCH
2019-07-29 15:00 ` [Qemu-devel] [Qemu-block] [PATCH v3 for-4.2 0/3] block: BDRV_REQ_PREFETCH Stefan Hajnoczi
@ 2019-07-29 15:29 ` Vladimir Sementsov-Ogievskiy
2019-07-29 15:38 ` Eric Blake
1 sibling, 0 replies; 10+ messages in thread
From: Vladimir Sementsov-Ogievskiy @ 2019-07-29 15:29 UTC (permalink / raw)
To: Stefan Hajnoczi
Cc: kwolf, fam, Denis Lunev, qemu-block, qemu-devel, mreitz, stefanha
29.07.2019 18:00, Stefan Hajnoczi wrote:
> On Thu, Jul 25, 2019 at 01:05:47PM +0300, Vladimir Sementsov-Ogievskiy wrote:
>> Hi all!
>>
>> Here is small new read flag: BDRV_REQ_PREFETCH, which in combination with
>> BDRV_REQ_COPY_ON_READ does copy-on-read without
>> extra buffer for read data. This means that only parts that needs COR
>> will be actually read and only corresponding buffers allocated, no more.
>>
>> This allows to improve a bit block-stream and NBD_CMD_CACHE
>>
>> v3: rebase 02 on master, fix commit message of 03.
>>
>> v2: change interface to be just one flag BDRV_REQ_PREFETCH
>>
>> v1 was "[PATCH 0/3] block: blk_co_pcache"
>> https://lists.gnu.org/archive/html/qemu-devel/2019-06/msg01047.html
>>
>> Vladimir Sementsov-Ogievskiy (3):
>> block: implement BDRV_REQ_PREFETCH
>> block/stream: use BDRV_REQ_PREFETCH
>> nbd: improve CMD_CACHE: use BDRV_REQ_PREFETCH
>>
>> include/block/block.h | 8 +++++++-
>> block/io.c | 18 ++++++++++++------
>> block/stream.c | 20 +++++++-------------
>> nbd/server.c | 43 +++++++++++++++++++++++++++++++++++--------
>> 4 files changed, 61 insertions(+), 28 deletions(-)
>>
>> --
>> 2.18.0
>>
>>
>
> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
>
Thank you for reviewing!
--
Best regards,
Vladimir
^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [Qemu-devel] [Qemu-block] [PATCH v3 for-4.2 0/3] block: BDRV_REQ_PREFETCH
2019-07-29 15:00 ` [Qemu-devel] [Qemu-block] [PATCH v3 for-4.2 0/3] block: BDRV_REQ_PREFETCH Stefan Hajnoczi
2019-07-29 15:29 ` Vladimir Sementsov-Ogievskiy
@ 2019-07-29 15:38 ` Eric Blake
1 sibling, 0 replies; 10+ messages in thread
From: Eric Blake @ 2019-07-29 15:38 UTC (permalink / raw)
To: Stefan Hajnoczi, Vladimir Sementsov-Ogievskiy
Cc: kwolf, fam, qemu-block, qemu-devel, mreitz, stefanha, den
[-- Attachment #1.1: Type: text/plain, Size: 1485 bytes --]
On 7/29/19 10:00 AM, Stefan Hajnoczi wrote:
> On Thu, Jul 25, 2019 at 01:05:47PM +0300, Vladimir Sementsov-Ogievskiy wrote:
>> Hi all!
>>
>> Here is small new read flag: BDRV_REQ_PREFETCH, which in combination with
>> BDRV_REQ_COPY_ON_READ does copy-on-read without
>> extra buffer for read data. This means that only parts that needs COR
>> will be actually read and only corresponding buffers allocated, no more.
>>
>> This allows to improve a bit block-stream and NBD_CMD_CACHE
>>
>> v3: rebase 02 on master, fix commit message of 03.
>>
>> v2: change interface to be just one flag BDRV_REQ_PREFETCH
>>
>> v1 was "[PATCH 0/3] block: blk_co_pcache"
>> https://lists.gnu.org/archive/html/qemu-devel/2019-06/msg01047.html
>>
>> Vladimir Sementsov-Ogievskiy (3):
>> block: implement BDRV_REQ_PREFETCH
>> block/stream: use BDRV_REQ_PREFETCH
>> nbd: improve CMD_CACHE: use BDRV_REQ_PREFETCH
>>
>> include/block/block.h | 8 +++++++-
>> block/io.c | 18 ++++++++++++------
>> block/stream.c | 20 +++++++-------------
>> nbd/server.c | 43 +++++++++++++++++++++++++++++++++++--------
>> 4 files changed, 61 insertions(+), 28 deletions(-)
>>
>> --
>> 2.18.0
>>
>>
>
> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
>
I'm happy to queue this one through my NBD tree for 4.2.
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3226
Virtualization: qemu.org | libvirt.org
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^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [Qemu-devel] [PATCH v3 1/3] block: implement BDRV_REQ_PREFETCH
2019-07-25 10:05 ` [Qemu-devel] [PATCH v3 1/3] block: implement BDRV_REQ_PREFETCH Vladimir Sementsov-Ogievskiy
@ 2019-07-29 21:13 ` Eric Blake
0 siblings, 0 replies; 10+ messages in thread
From: Eric Blake @ 2019-07-29 21:13 UTC (permalink / raw)
To: Vladimir Sementsov-Ogievskiy, qemu-devel, qemu-block
Cc: kwolf, fam, mreitz, stefanha, den, jsnow
[-- Attachment #1.1: Type: text/plain, Size: 1874 bytes --]
On 7/25/19 5:05 AM, Vladimir Sementsov-Ogievskiy wrote:
> Do effective copy-on-read request when we don't need data actually. It
> will be used for block-stream and NBD_CMD_CACHE.
>
> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
> ---
> include/block/block.h | 8 +++++++-
> block/io.c | 18 ++++++++++++------
> 2 files changed, 19 insertions(+), 7 deletions(-)
>
> diff --git a/include/block/block.h b/include/block/block.h
> index 50a07c1c33..73c3fc4daa 100644
> --- a/include/block/block.h
> +++ b/include/block/block.h
> @@ -88,8 +88,14 @@ typedef enum {
> * fallback. */
> BDRV_REQ_NO_FALLBACK = 0x100,
>
> + /*
> + * BDRV_REQ_PREFETCH may be used only together with BDRV_REQ_COPY_ON_READ
> + * on read request and means that caller don't really need data to be
doesn't
can fix up while staging.
> +++ b/block/io.c
> @@ -1167,7 +1167,8 @@ bdrv_driver_pwritev_compressed(BlockDriverState *bs, uint64_t offset,
> }
>
> static int coroutine_fn bdrv_co_do_copy_on_readv(BdrvChild *child,
> - int64_t offset, unsigned int bytes, QEMUIOVector *qiov)
> + int64_t offset, unsigned int bytes, QEMUIOVector *qiov,
> + int flags)
We're bad about this, but 'int flags' does not play well with the C
language and well-defined behavior when it comes to 1<<31 (bit
operations and unsigned types have guaranteed behavior, bit operations
and negative signed types can cause the compiler to do differently than
you expect). Not a problem for uses where we don't have 32 flags to OR
together, so I won't change it, so much as point it out for a bigger
task of auditing the entire code base if we are worried.
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3226
Virtualization: qemu.org | libvirt.org
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* Re: [Qemu-devel] [PATCH v3 2/3] block/stream: use BDRV_REQ_PREFETCH
2019-07-25 10:05 ` [Qemu-devel] [PATCH v3 2/3] block/stream: use BDRV_REQ_PREFETCH Vladimir Sementsov-Ogievskiy
@ 2019-07-29 21:19 ` Eric Blake
0 siblings, 0 replies; 10+ messages in thread
From: Eric Blake @ 2019-07-29 21:19 UTC (permalink / raw)
To: Vladimir Sementsov-Ogievskiy, qemu-devel, qemu-block
Cc: kwolf, fam, mreitz, stefanha, den, jsnow
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On 7/25/19 5:05 AM, Vladimir Sementsov-Ogievskiy wrote:
> This helps to avoid extra io, allocations and memory copying.
>
> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
> ---
> block/stream.c | 20 +++++++-------------
> 1 file changed, 7 insertions(+), 13 deletions(-)
>
> diff --git a/block/stream.c b/block/stream.c
> index 6ac1e7bec4..170e3b43be 100644
> --- a/block/stream.c
> +++ b/block/stream.c
> @@ -22,11 +22,11 @@
>
> enum {
> /*
> - * Size of data buffer for populating the image file. This should be large
> + * Maximum chunk size to feed it to copy-on-read. This should be large
s/feed it/feed/
Will fix during staging
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3226
Virtualization: qemu.org | libvirt.org
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* Re: [Qemu-devel] [PATCH v3 3/3] nbd: improve CMD_CACHE: use BDRV_REQ_PREFETCH
2019-07-25 10:05 ` [Qemu-devel] [PATCH v3 3/3] nbd: improve CMD_CACHE: " Vladimir Sementsov-Ogievskiy
@ 2019-07-29 21:24 ` Eric Blake
0 siblings, 0 replies; 10+ messages in thread
From: Eric Blake @ 2019-07-29 21:24 UTC (permalink / raw)
To: Vladimir Sementsov-Ogievskiy, qemu-devel, qemu-block
Cc: kwolf, fam, mreitz, stefanha, den, jsnow
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On 7/25/19 5:05 AM, Vladimir Sementsov-Ogievskiy wrote:
> This helps to avoid extra io, allocations and memory copying.
> We assume here that CMD_CACHE is always used with copy-on-read, as
> otherwise it's a noop.
>
> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
> ---
> nbd/server.c | 43 +++++++++++++++++++++++++++++++++++--------
> 1 file changed, 35 insertions(+), 8 deletions(-)
libnbd is able to test NBD_CMD_CACHE requests, and I've confirmed that
behavior looks sane under requests issued that way. I'm wondering if
qemu-io should also be able to drive this mode of operation, so that we
can give it iotest coverage without depending on libnbd.
Reviewed-by: Eric Blake <eblake@redhat.com>
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3226
Virtualization: qemu.org | libvirt.org
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^ permalink raw reply [flat|nested] 10+ messages in thread
end of thread, other threads:[~2019-07-29 21:25 UTC | newest]
Thread overview: 10+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2019-07-25 10:05 [Qemu-devel] [PATCH v3 for-4.2 0/3] block: BDRV_REQ_PREFETCH Vladimir Sementsov-Ogievskiy
2019-07-25 10:05 ` [Qemu-devel] [PATCH v3 1/3] block: implement BDRV_REQ_PREFETCH Vladimir Sementsov-Ogievskiy
2019-07-29 21:13 ` Eric Blake
2019-07-25 10:05 ` [Qemu-devel] [PATCH v3 2/3] block/stream: use BDRV_REQ_PREFETCH Vladimir Sementsov-Ogievskiy
2019-07-29 21:19 ` Eric Blake
2019-07-25 10:05 ` [Qemu-devel] [PATCH v3 3/3] nbd: improve CMD_CACHE: " Vladimir Sementsov-Ogievskiy
2019-07-29 21:24 ` Eric Blake
2019-07-29 15:00 ` [Qemu-devel] [Qemu-block] [PATCH v3 for-4.2 0/3] block: BDRV_REQ_PREFETCH Stefan Hajnoczi
2019-07-29 15:29 ` Vladimir Sementsov-Ogievskiy
2019-07-29 15:38 ` Eric Blake
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