From patchwork Thu Mar 21 14:49:57 2013 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Stefan Hajnoczi X-Patchwork-Id: 229722 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Received: from lists.gnu.org (lists.gnu.org [208.118.235.17]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (Client did not present a certificate) by ozlabs.org (Postfix) with ESMTPS id 257032C00C0 for ; Fri, 22 Mar 2013 01:51:26 +1100 (EST) Received: from localhost ([::1]:52805 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1UIgpw-0003GC-BB for incoming@patchwork.ozlabs.org; Thu, 21 Mar 2013 10:51:24 -0400 Received: from eggs.gnu.org ([208.118.235.92]:44100) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1UIgp8-0003AJ-70 for qemu-devel@nongnu.org; Thu, 21 Mar 2013 10:50:41 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1UIgp2-0002I3-H8 for qemu-devel@nongnu.org; Thu, 21 Mar 2013 10:50:34 -0400 Received: from mx1.redhat.com ([209.132.183.28]:55627) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1UIgp2-0002HX-9K for qemu-devel@nongnu.org; Thu, 21 Mar 2013 10:50:28 -0400 Received: from int-mx02.intmail.prod.int.phx2.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id r2LEoI79003891 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK); Thu, 21 Mar 2013 10:50:20 -0400 Received: from localhost (ovpn-112-35.ams2.redhat.com [10.36.112.35]) by int-mx02.intmail.prod.int.phx2.redhat.com (8.13.8/8.13.8) with ESMTP id r2LEoGjf000978; Thu, 21 Mar 2013 10:50:17 -0400 From: Stefan Hajnoczi To: Date: Thu, 21 Mar 2013 15:49:57 +0100 Message-Id: <1363877399-16339-3-git-send-email-stefanha@redhat.com> In-Reply-To: <1363877399-16339-1-git-send-email-stefanha@redhat.com> References: <1363877399-16339-1-git-send-email-stefanha@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.67 on 10.5.11.12 X-MIME-Autoconverted: from 8bit to quoted-printable by mx1.redhat.com id r2LEoI79003891 X-detected-operating-system: by eggs.gnu.org: GNU/Linux 3.x X-Received-From: 209.132.183.28 Cc: Kevin Wolf , =?UTF-8?q?Beno=C3=AEt=20Canet?= , Stefan Hajnoczi , Zhi Yong Wu Subject: [Qemu-devel] [RFC 2/4] block: keep I/O throttling slice time constant X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org It is not necessary to adjust the slice time at runtime. We already extend the current slice in order to carry over accounting into the next slice. Changing the actual slice time value introduces oscillations. The guest may experience large changes in throughput or IOPS from one moment to the next when slice times are adjusted. Reported-by: Benoît Canet Signed-off-by: Stefan Hajnoczi --- block.c | 19 +++++++++---------- blockdev.c | 1 - include/block/block_int.h | 1 - 3 files changed, 9 insertions(+), 12 deletions(-) diff --git a/block.c b/block.c index 31fb0b0..712f544 100644 --- a/block.c +++ b/block.c @@ -140,7 +140,6 @@ void bdrv_io_limits_disable(BlockDriverState *bs) bs->slice_start = 0; bs->slice_end = 0; - bs->slice_time = 0; } static void bdrv_block_timer(void *opaque) @@ -1325,7 +1324,6 @@ static void bdrv_move_feature_fields(BlockDriverState *bs_dest, bs_dest->enable_write_cache = bs_src->enable_write_cache; /* i/o timing parameters */ - bs_dest->slice_time = bs_src->slice_time; bs_dest->slice_start = bs_src->slice_start; bs_dest->slice_end = bs_src->slice_end; bs_dest->slice_submitted = bs_src->slice_submitted; @@ -3646,6 +3644,7 @@ static bool bdrv_exceed_bps_limits(BlockDriverState *bs, int nb_sectors, bool is_write, double elapsed_time, uint64_t *wait) { uint64_t bps_limit = 0; + uint64_t extension; double bytes_limit, bytes_base, bytes_res; double slice_time, wait_time; @@ -3694,8 +3693,10 @@ static bool bdrv_exceed_bps_limits(BlockDriverState *bs, int nb_sectors, * info can be kept until the timer fire, so it is increased and tuned * based on the result of experiment. */ - bs->slice_time = wait_time * BLOCK_IO_SLICE_TIME * 10; - bs->slice_end += bs->slice_time - 3 * BLOCK_IO_SLICE_TIME; + extension = wait_time * NANOSECONDS_PER_SECOND; + extension = DIV_ROUND_UP(extension, BLOCK_IO_SLICE_TIME) * + BLOCK_IO_SLICE_TIME; + bs->slice_end += extension; if (wait) { *wait = wait_time * BLOCK_IO_SLICE_TIME * 10; } @@ -3747,8 +3748,8 @@ static bool bdrv_exceed_iops_limits(BlockDriverState *bs, bool is_write, wait_time = 0; } - bs->slice_time = wait_time * BLOCK_IO_SLICE_TIME * 10; - bs->slice_end += bs->slice_time - 3 * BLOCK_IO_SLICE_TIME; + /* Exceeded current slice, extend it by another slice time */ + bs->slice_end += BLOCK_IO_SLICE_TIME; if (wait) { *wait = wait_time * BLOCK_IO_SLICE_TIME * 10; } @@ -3767,12 +3768,10 @@ static bool bdrv_exceed_io_limits(BlockDriverState *bs, int nb_sectors, now = qemu_get_clock_ns(vm_clock); if ((bs->slice_start < now) && (bs->slice_end > now)) { - bs->slice_end = now + bs->slice_time; + bs->slice_end = now + BLOCK_IO_SLICE_TIME; } else { - bs->slice_time = 5 * BLOCK_IO_SLICE_TIME; bs->slice_start = now; - bs->slice_end = now + bs->slice_time; - + bs->slice_end = now + BLOCK_IO_SLICE_TIME; memset(&bs->slice_submitted, 0, sizeof(bs->slice_submitted)); } diff --git a/blockdev.c b/blockdev.c index 09f76b7..e5ead1f 100644 --- a/blockdev.c +++ b/blockdev.c @@ -1065,7 +1065,6 @@ void qmp_block_set_io_throttle(const char *device, int64_t bps, int64_t bps_rd, } bs->io_limits = io_limits; - bs->slice_time = BLOCK_IO_SLICE_TIME; if (!bs->io_limits_enabled && bdrv_io_limits_enabled(bs)) { bdrv_io_limits_enable(bs); diff --git a/include/block/block_int.h b/include/block/block_int.h index b461764..ec75802 100644 --- a/include/block/block_int.h +++ b/include/block/block_int.h @@ -247,7 +247,6 @@ struct BlockDriverState { unsigned int copy_on_read_in_flight; /* the time for latest disk I/O */ - int64_t slice_time; int64_t slice_start; int64_t slice_end; BlockIOLimit io_limits;