From patchwork Fri Apr 5 13:28:06 2013 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Kevin Wolf X-Patchwork-Id: 234138 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 90D1B2C00AB for ; Sat, 6 Apr 2013 00:33:06 +1100 (EST) Received: from localhost ([::1]:35901 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1UO6lM-00021I-QT for incoming@patchwork.ozlabs.org; Fri, 05 Apr 2013 09:33:04 -0400 Received: from eggs.gnu.org ([208.118.235.92]:48593) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1UO6gu-0003Xv-83 for qemu-devel@nongnu.org; Fri, 05 Apr 2013 09:28:37 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1UO6gr-0007z8-Lp for qemu-devel@nongnu.org; Fri, 05 Apr 2013 09:28:28 -0400 Received: from mx1.redhat.com ([209.132.183.28]:61354) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1UO6gr-0007yp-Ea for qemu-devel@nongnu.org; Fri, 05 Apr 2013 09:28:25 -0400 Received: from int-mx01.intmail.prod.int.phx2.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id r35DSOku028804 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK); Fri, 5 Apr 2013 09:28:24 -0400 Received: from dhcp-200-207.str.redhat.com (ovpn-116-95.ams2.redhat.com [10.36.116.95]) by int-mx01.intmail.prod.int.phx2.redhat.com (8.13.8/8.13.8) with ESMTP id r35DSG3o003635; Fri, 5 Apr 2013 09:28:23 -0400 From: Kevin Wolf To: anthony@codemonkey.ws Date: Fri, 5 Apr 2013 15:28:06 +0200 Message-Id: <1365168490-29616-5-git-send-email-kwolf@redhat.com> In-Reply-To: <1365168490-29616-1-git-send-email-kwolf@redhat.com> References: <1365168490-29616-1-git-send-email-kwolf@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.67 on 10.5.11.11 X-MIME-Autoconverted: from 8bit to quoted-printable by mx1.redhat.com id r35DSOku028804 X-detected-operating-system: by eggs.gnu.org: GNU/Linux 3.x X-Received-From: 209.132.183.28 Cc: kwolf@redhat.com, qemu-devel@nongnu.org Subject: [Qemu-devel] [PATCH 4/8] 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 From: Stefan Hajnoczi 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 Tested-By: Benoit Canet Signed-off-by: Kevin Wolf --- 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 25976b5..00eca27 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) @@ -1432,7 +1431,6 @@ 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; @@ -3749,6 +3747,7 @@ 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; @@ -3796,8 +3795,10 @@ 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; } @@ -3848,8 +3849,8 @@ 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; } @@ -3868,12 +3869,10 @@ 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 8cdc9ce..6dc999d 100644 --- a/blockdev.c +++ b/blockdev.c @@ -1069,7 +1069,6 @@ 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 83941d8..9aa98b5 100644 --- a/include/block/block_int.h +++ b/include/block/block_int.h @@ -252,7 +252,6 @@ 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;