[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [Qemu-devel] [PATCH 2/2] block/nfs: try to avoid the bounce buffer i
From: |
Jeff Cody |
Subject: |
Re: [Qemu-devel] [PATCH 2/2] block/nfs: try to avoid the bounce buffer in pwritev |
Date: |
Fri, 17 Feb 2017 16:51:17 -0500 |
User-agent: |
Mutt/1.5.24 (2015-08-30) |
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 <address@hidden>
> >> ---
> >> 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 <address@hidden>
[Qemu-devel] [PATCH 1/2] block/nfs: convert to preadv / pwritev, Peter Lieven, 2017/02/17
Re: [Qemu-devel] [PATCH 0/2] block/nfs optimizations, Jeff Cody, 2017/02/23