Received: from eggs.gnu.org ([2001:4830:134:3::10]:48154) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YiioI-0001yc-Ku for qemu-devel@nongnu.org; Thu, 16 Apr 2015 08:22:26 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Yiio8-0006D4-LE for qemu-devel@nongnu.org; Thu, 16 Apr 2015 08:22:22 -0400 Received: from mx-v6.kamp.de ([2a02:248:0:51::16]:49761 helo=mx01.kamp.de) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Yiio8-0006By-AK for qemu-devel@nongnu.org; Thu, 16 Apr 2015 08:22:12 -0400 From: Peter Lieven Date: Thu, 16 Apr 2015 14:18:45 +0200 Message-Id: <1429186730-3866-6-git-send-email-pl@kamp.de> In-Reply-To: <1429186730-3866-1-git-send-email-pl@kamp.de> References: <1429186730-3866-1-git-send-email-pl@kamp.de> Subject: [Qemu-devel] [PATCH for-2.4 05/10] block/iscsi: optimize WRITE10/16 if cache.writeback is not set List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: pbonzini@redhat.com, Peter Lieven , ronniesahlberg@gmail.com, qemu-block@nongnu.org SCSI allowes to tell the target to not return from a write command if the date is not written to the disk. Use this so called FUA bit if it is supported to optimize WRITE commands if writeback is not allowed. In this case qemu always issues a WRITE followed by a FLUSH. This is 2 round trip times. If we set the FUA bit we can ignore the following FLUSH. Signed-off-by: Peter Lieven --- block/iscsi.c | 15 +++++++++++++-- 1 file changed, 13 insertions(+), 2 deletions(-) diff --git a/block/iscsi.c b/block/iscsi.c index 237faa1..7fb04d7 100644 --- a/block/iscsi.c +++ b/block/iscsi.c @@ -68,6 +68,7 @@ typedef struct IscsiLun { bool lbprz; bool dpofua; bool has_write_same; + bool force_next_flush; } IscsiLun; typedef struct IscsiTask { @@ -370,6 +371,7 @@ static int coroutine_fn iscsi_co_writev(BlockDriverState *bs, struct IscsiTask iTask; uint64_t lba; uint32_t num_sectors; + int fua = iscsilun->dpofua && !bs->enable_write_cache; if (!is_request_lun_aligned(sector_num, nb_sectors, iscsilun)) { return -EINVAL; @@ -388,12 +390,12 @@ retry: if (iscsilun->use_16_for_rw) { iTask.task = iscsi_write16_task(iscsilun->iscsi, iscsilun->lun, lba, NULL, num_sectors * iscsilun->block_size, - iscsilun->block_size, 0, 0, 0, 0, 0, + iscsilun->block_size, 0, 0, fua, 0, 0, iscsi_co_generic_cb, &iTask); } else { iTask.task = iscsi_write10_task(iscsilun->iscsi, iscsilun->lun, lba, NULL, num_sectors * iscsilun->block_size, - iscsilun->block_size, 0, 0, 0, 0, 0, + iscsilun->block_size, 0, 0, fua, 0, 0, iscsi_co_generic_cb, &iTask); } if (iTask.task == NULL) { @@ -621,6 +623,11 @@ static int coroutine_fn iscsi_co_flush(BlockDriverState *bs) return 0; } + if (iscsilun->dpofua && !bs->enable_write_cache && + !iscsilun->force_next_flush) { + return 0; + } + iscsi_co_init_iscsitask(iscsilun, &iTask); retry: @@ -648,6 +655,8 @@ retry: return -EIO; } + iscsilun->force_next_flush = false; + return 0; } @@ -969,6 +978,8 @@ retry: iscsi_allocationmap_set(iscsilun, sector_num, nb_sectors); } + iscsilun->force_next_flush = true; + return 0; } -- 1.9.1