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[Qemu-devel] [PATCH 2/2] block/nfs: try to avoid the bounce buffer in pwritev

Peter Lieven posted 2 patches 8 years, 11 months ago
[Qemu-devel] [PATCH 2/2] block/nfs: try to avoid the bounce buffer in pwritev
Posted by Peter Lieven 8 years, 11 months ago 
if the passed qiov contains exactly one iov we can
pass the buffer directly.

Signed-off-by: Peter Lieven <pl@kamp.de>
---
 block/nfs.c | 23 ++++++++++++++++-------
 1 file changed, 16 insertions(+), 7 deletions(-)

diff --git a/block/nfs.c b/block/nfs.c
index ab5dcc2..bb4b75f 100644
--- a/block/nfs.c
+++ b/block/nfs.c
@@ -295,20 +295,27 @@ static int coroutine_fn nfs_co_pwritev(BlockDriverState *bs, uint64_t offset,
     NFSClient *client = bs->opaque;
     NFSRPC task;
     char *buf = NULL;
+    bool my_buffer = false;
 
     nfs_co_init_task(bs, &task);
 
-    buf = g_try_malloc(bytes);
-    if (bytes && buf == NULL) {
-        return -ENOMEM;
+    if (iov->niov != 1) {
+        buf = g_try_malloc(bytes);
+        if (bytes && buf == NULL) {
+            return -ENOMEM;
+        }
+        qemu_iovec_to_buf(iov, 0, buf, bytes);
+        my_buffer = true;
+    } else {
+        buf = iov->iov[0].iov_base;
     }
 
-    qemu_iovec_to_buf(iov, 0, buf, bytes);
-
     if (nfs_pwrite_async(client->context, client->fh,
                          offset, bytes, buf,
                          nfs_co_generic_cb, &task) != 0) {
-        g_free(buf);
+        if (my_buffer) {
+            g_free(buf);
+        }
         return -ENOMEM;
     }
 
@@ -317,7 +324,9 @@ static int coroutine_fn nfs_co_pwritev(BlockDriverState *bs, uint64_t offset,
         qemu_coroutine_yield();
     }
 
-    g_free(buf);
+    if (my_buffer) {
+        g_free(buf);
+    }
 
     if (task.ret != bytes) {
         return task.ret < 0 ? task.ret : -EIO;
-- 
1.9.1
Re: [Qemu-devel] [PATCH 2/2] block/nfs: try to avoid the bounce buffer in pwritev
Posted by Jeff Cody 8 years, 11 months ago 
On Fri, Feb 17, 2017 at 05:39:01PM +0100, Peter Lieven wrote:
> if the passed qiov contains exactly one iov we can
> pass the buffer directly.
> 
> Signed-off-by: Peter Lieven <pl@kamp.de>
> ---
>  block/nfs.c | 23 ++++++++++++++++-------
>  1 file changed, 16 insertions(+), 7 deletions(-)
> 
> diff --git a/block/nfs.c b/block/nfs.c
> index ab5dcc2..bb4b75f 100644
> --- a/block/nfs.c
> +++ b/block/nfs.c
> @@ -295,20 +295,27 @@ static int coroutine_fn nfs_co_pwritev(BlockDriverState *bs, uint64_t offset,
>      NFSClient *client = bs->opaque;
>      NFSRPC task;
>      char *buf = NULL;
> +    bool my_buffer = false;

g_free() is a nop if buf is NULL, so there is no need for the my_buffer
variable & check.

>  
>      nfs_co_init_task(bs, &task);
>  
> -    buf = g_try_malloc(bytes);
> -    if (bytes && buf == NULL) {
> -        return -ENOMEM;
> +    if (iov->niov != 1) {
> +        buf = g_try_malloc(bytes);
> +        if (bytes && buf == NULL) {
> +            return -ENOMEM;
> +        }
> +        qemu_iovec_to_buf(iov, 0, buf, bytes);
> +        my_buffer = true;
> +    } else {
> +        buf = iov->iov[0].iov_base;
>      }
>  
> -    qemu_iovec_to_buf(iov, 0, buf, bytes);
> -
>      if (nfs_pwrite_async(client->context, client->fh,
>                           offset, bytes, buf,
>                           nfs_co_generic_cb, &task) != 0) {
> -        g_free(buf);
> +        if (my_buffer) {
> +            g_free(buf);
> +        }
>          return -ENOMEM;
>      }
>  
> @@ -317,7 +324,9 @@ static int coroutine_fn nfs_co_pwritev(BlockDriverState *bs, uint64_t offset,
>          qemu_coroutine_yield();
>      }
>  
> -    g_free(buf);
> +    if (my_buffer) {
> +        g_free(buf);
> +    }
>  
>      if (task.ret != bytes) {
>          return task.ret < 0 ? task.ret : -EIO;
> -- 
> 1.9.1
>
Re: [Qemu-devel] [PATCH 2/2] block/nfs: try to avoid the bounce buffer in pwritev
Posted by Eric Blake 8 years, 11 months ago 
On 02/17/2017 03:37 PM, Jeff Cody wrote:
> On Fri, Feb 17, 2017 at 05:39:01PM +0100, Peter Lieven wrote:
>> if the passed qiov contains exactly one iov we can
>> pass the buffer directly.
>>
>> Signed-off-by: Peter Lieven <pl@kamp.de>
>> ---
>>  block/nfs.c | 23 ++++++++++++++++-------
>>  1 file changed, 16 insertions(+), 7 deletions(-)
>>
>> diff --git a/block/nfs.c b/block/nfs.c
>> index ab5dcc2..bb4b75f 100644
>> --- a/block/nfs.c
>> +++ b/block/nfs.c
>> @@ -295,20 +295,27 @@ static int coroutine_fn nfs_co_pwritev(BlockDriverState *bs, uint64_t offset,
>>      NFSClient *client = bs->opaque;
>>      NFSRPC task;
>>      char *buf = NULL;
>> +    bool my_buffer = false;
> 
> g_free() is a nop if buf is NULL, so there is no need for the my_buffer
> variable & check.

Umm, yes there is:

>> +    if (iov->niov != 1) {
>> +        buf = g_try_malloc(bytes);
>> +        if (bytes && buf == NULL) {
>> +            return -ENOMEM;
>> +        }
>> +        qemu_iovec_to_buf(iov, 0, buf, bytes);
>> +        my_buffer = true;
>> +    } else {
>> +        buf = iov->iov[0].iov_base;

If we took the else branch, then we definitely do not want to be calling
g_free(buf).

>>      }
>>  
>> -    qemu_iovec_to_buf(iov, 0, buf, bytes);
>> -
>>      if (nfs_pwrite_async(client->context, client->fh,
>>                           offset, bytes, buf,
>>                           nfs_co_generic_cb, &task) != 0) {
>> -        g_free(buf);
>> +        if (my_buffer) {
>> +            g_free(buf);
>> +        }

It looks correct as-is to me.

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org
Re: [Qemu-devel] [PATCH 2/2] block/nfs: try to avoid the bounce buffer in pwritev
Posted by Jeff Cody 8 years, 11 months ago 
On Fri, Feb 17, 2017 at 03:42:52PM -0600, Eric Blake wrote:
> On 02/17/2017 03:37 PM, Jeff Cody wrote:
> > On Fri, Feb 17, 2017 at 05:39:01PM +0100, Peter Lieven wrote:
> >> if the passed qiov contains exactly one iov we can
> >> pass the buffer directly.
> >>
> >> Signed-off-by: Peter Lieven <pl@kamp.de>
> >> ---
> >>  block/nfs.c | 23 ++++++++++++++++-------
> >>  1 file changed, 16 insertions(+), 7 deletions(-)
> >>
> >> diff --git a/block/nfs.c b/block/nfs.c
> >> index ab5dcc2..bb4b75f 100644
> >> --- a/block/nfs.c
> >> +++ b/block/nfs.c
> >> @@ -295,20 +295,27 @@ static int coroutine_fn nfs_co_pwritev(BlockDriverState *bs, uint64_t offset,
> >>      NFSClient *client = bs->opaque;
> >>      NFSRPC task;
> >>      char *buf = NULL;
> >> +    bool my_buffer = false;
> > 
> > g_free() is a nop if buf is NULL, so there is no need for the my_buffer
> > variable & check.
> 
> Umm, yes there is:
> 
> >> +    if (iov->niov != 1) {
> >> +        buf = g_try_malloc(bytes);
> >> +        if (bytes && buf == NULL) {
> >> +            return -ENOMEM;
> >> +        }
> >> +        qemu_iovec_to_buf(iov, 0, buf, bytes);
> >> +        my_buffer = true;
> >> +    } else {
> >> +        buf = iov->iov[0].iov_base;
> 
> If we took the else branch, then we definitely do not want to be calling
> g_free(buf).

Doh!

> 
> >>      }
> >>  
> >> -    qemu_iovec_to_buf(iov, 0, buf, bytes);
> >> -
> >>      if (nfs_pwrite_async(client->context, client->fh,
> >>                           offset, bytes, buf,
> >>                           nfs_co_generic_cb, &task) != 0) {
> >> -        g_free(buf);
> >> +        if (my_buffer) {
> >> +            g_free(buf);
> >> +        }
> 
> It looks correct as-is to me.

Indeed.

Reviewed-by: Jeff Cody <jcody@redhat.com>
Re: [Qemu-devel] [PATCH 2/2] block/nfs: try to avoid the bounce buffer in pwritev
Posted by Kevin Wolf 8 years, 11 months ago 
Am 17.02.2017 um 22:51 hat Jeff Cody geschrieben:
> On Fri, Feb 17, 2017 at 03:42:52PM -0600, Eric Blake wrote:
> > On 02/17/2017 03:37 PM, Jeff Cody wrote:
> > > On Fri, Feb 17, 2017 at 05:39:01PM +0100, Peter Lieven wrote:
> > >> if the passed qiov contains exactly one iov we can
> > >> pass the buffer directly.
> > >>
> > >> Signed-off-by: Peter Lieven <pl@kamp.de>
> > >> ---
> > >>  block/nfs.c | 23 ++++++++++++++++-------
> > >>  1 file changed, 16 insertions(+), 7 deletions(-)
> > >>
> > >> diff --git a/block/nfs.c b/block/nfs.c
> > >> index ab5dcc2..bb4b75f 100644
> > >> --- a/block/nfs.c
> > >> +++ b/block/nfs.c
> > >> @@ -295,20 +295,27 @@ static int coroutine_fn nfs_co_pwritev(BlockDriverState *bs, uint64_t offset,
> > >>      NFSClient *client = bs->opaque;
> > >>      NFSRPC task;
> > >>      char *buf = NULL;
> > >> +    bool my_buffer = false;
> > > 
> > > g_free() is a nop if buf is NULL, so there is no need for the my_buffer
> > > variable & check.
> > 
> > Umm, yes there is:
> > 
> > >> +    if (iov->niov != 1) {
> > >> +        buf = g_try_malloc(bytes);
> > >> +        if (bytes && buf == NULL) {
> > >> +            return -ENOMEM;
> > >> +        }
> > >> +        qemu_iovec_to_buf(iov, 0, buf, bytes);
> > >> +        my_buffer = true;
> > >> +    } else {
> > >> +        buf = iov->iov[0].iov_base;
> > 
> > If we took the else branch, then we definitely do not want to be calling
> > g_free(buf).
> 
> Doh!
> 
> > 
> > >>      }
> > >>  
> > >> -    qemu_iovec_to_buf(iov, 0, buf, bytes);
> > >> -
> > >>      if (nfs_pwrite_async(client->context, client->fh,
> > >>                           offset, bytes, buf,
> > >>                           nfs_co_generic_cb, &task) != 0) {
> > >> -        g_free(buf);
> > >> +        if (my_buffer) {
> > >> +            g_free(buf);
> > >> +        }
> > 
> > It looks correct as-is to me.
> 
> Indeed.
> 
> Reviewed-by: Jeff Cody <jcody@redhat.com>

You gave R-b for both patches, but did not merge it - who is supposed to
do that?

Kevin
Re: [Qemu-devel] [PATCH 2/2] block/nfs: try to avoid the bounce buffer in pwritev
Posted by Jeff Cody 8 years, 11 months ago 
On Wed, Feb 22, 2017 at 01:47:10PM +0100, Kevin Wolf wrote:
> Am 17.02.2017 um 22:51 hat Jeff Cody geschrieben:
> > On Fri, Feb 17, 2017 at 03:42:52PM -0600, Eric Blake wrote:
> > > On 02/17/2017 03:37 PM, Jeff Cody wrote:
> > > > On Fri, Feb 17, 2017 at 05:39:01PM +0100, Peter Lieven wrote:
> > > >> if the passed qiov contains exactly one iov we can
> > > >> pass the buffer directly.
> > > >>
> > > >> Signed-off-by: Peter Lieven <pl@kamp.de>
> > > >> ---
> > > >>  block/nfs.c | 23 ++++++++++++++++-------
> > > >>  1 file changed, 16 insertions(+), 7 deletions(-)
> > > >>
> > > >> diff --git a/block/nfs.c b/block/nfs.c
> > > >> index ab5dcc2..bb4b75f 100644
> > > >> --- a/block/nfs.c
> > > >> +++ b/block/nfs.c
> > > >> @@ -295,20 +295,27 @@ static int coroutine_fn nfs_co_pwritev(BlockDriverState *bs, uint64_t offset,
> > > >>      NFSClient *client = bs->opaque;
> > > >>      NFSRPC task;
> > > >>      char *buf = NULL;
> > > >> +    bool my_buffer = false;
> > > > 
> > > > g_free() is a nop if buf is NULL, so there is no need for the my_buffer
> > > > variable & check.
> > > 
> > > Umm, yes there is:
> > > 
> > > >> +    if (iov->niov != 1) {
> > > >> +        buf = g_try_malloc(bytes);
> > > >> +        if (bytes && buf == NULL) {
> > > >> +            return -ENOMEM;
> > > >> +        }
> > > >> +        qemu_iovec_to_buf(iov, 0, buf, bytes);
> > > >> +        my_buffer = true;
> > > >> +    } else {
> > > >> +        buf = iov->iov[0].iov_base;
> > > 
> > > If we took the else branch, then we definitely do not want to be calling
> > > g_free(buf).
> > 
> > Doh!
> > 
> > > 
> > > >>      }
> > > >>  
> > > >> -    qemu_iovec_to_buf(iov, 0, buf, bytes);
> > > >> -
> > > >>      if (nfs_pwrite_async(client->context, client->fh,
> > > >>                           offset, bytes, buf,
> > > >>                           nfs_co_generic_cb, &task) != 0) {
> > > >> -        g_free(buf);
> > > >> +        if (my_buffer) {
> > > >> +            g_free(buf);
> > > >> +        }
> > > 
> > > It looks correct as-is to me.
> > 
> > Indeed.
> > 
> > Reviewed-by: Jeff Cody <jcody@redhat.com>
> 
> You gave R-b for both patches, but did not merge it - who is supposed to
> do that?
>

I am going to do it in my next round, I was just waiting to see if there
were any other comments.

Patchew 2.1-devel-b67e4c2

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