From patchwork Mon Nov 19 14:58:31 2012 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Subject: iscsi: partly avoid iovec linearization in iscsi_aio_writev Date: Mon, 19 Nov 2012 04:58:31 -0000 From: Peter Lieven X-Patchwork-Id: 200023 Message-Id: <50AA4917.5000402@dlhnet.de> To: "qemu-devel@nongnu.org" Cc: kwolf@redhat.com, Paolo Bonzini , ronnie sahlberg libiscsi expects all write16 data in a linear buffer. If the iovec only contains one buffer we can skip the linearization step as well as the additional malloc/free and pass the buffer directly. Reported-by: Ronnie Sahlberg Signed-off-by: Peter Lieven Reviewed-by: Stefan Hajnoczi --- block/iscsi.c | 24 +++++++++++++++--------- 1 file changed, 15 insertions(+), 9 deletions(-) diff --git a/block/iscsi.c b/block/iscsi.c index d0b1a10..f12148e 100644 --- a/block/iscsi.c +++ b/block/iscsi.c @@ -199,8 +199,10 @@ iscsi_aio_write16_cb(struct iscsi_context *iscsi, int status, trace_iscsi_aio_write16_cb(iscsi, status, acb, acb->canceled); - g_free(acb->buf); - + if (acb->buf != NULL) { + g_free(acb->buf); + } + if (acb->canceled != 0) { return; } @@ -244,11 +246,18 @@ iscsi_aio_writev(BlockDriverState *bs, int64_t sector_num, acb->bh = NULL; acb->status = -EINPROGRESS; - /* XXX we should pass the iovec to write16 to avoid the extra copy */ - /* this will allow us to get rid of 'buf' completely */ size = nb_sectors * BDRV_SECTOR_SIZE; - acb->buf = g_malloc(size); - qemu_iovec_to_buf(acb->qiov, 0, acb->buf, size); + data.size = size; + + /* if the iovec only contains one buffer we can pass it directly */ + if (acb->qiov->niov == 1) { + acb->buf = NULL; + data.data = acb->qiov->iov[0].iov_base; + } else { + acb->buf = g_malloc(size); + qemu_iovec_to_buf(acb->qiov, 0, acb->buf, size); + data.data = acb->buf; + } acb->task = malloc(sizeof(struct scsi_task)); if (acb->task == NULL) { @@ -269,9 +278,6 @@ iscsi_aio_writev(BlockDriverState *bs, int64_t sector_num, *(uint32_t *)&acb->task->cdb[10] = htonl(num_sectors); acb->task->expxferlen = size; - data.data = acb->buf; - data.size = size; - if (iscsi_scsi_command_async(iscsi, iscsilun->lun, acb->task, iscsi_aio_write16_cb, &data,