From patchwork Thu Feb 15 09:42:09 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Stefan Hajnoczi X-Patchwork-Id: 873729 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Authentication-Results: ozlabs.org; spf=pass (mailfrom) smtp.mailfrom=nongnu.org (client-ip=2001:4830:134:3::11; helo=lists.gnu.org; envelope-from=qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org; receiver=) Received: from lists.gnu.org (lists.gnu.org [IPv6:2001:4830:134:3::11]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id 3zhsCR4mcfz9t2f for ; Thu, 15 Feb 2018 20:57:55 +1100 (AEDT) Received: from localhost ([::1]:58527 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1emGIb-0004m6-OS for incoming@patchwork.ozlabs.org; Thu, 15 Feb 2018 04:57:53 -0500 Received: from eggs.gnu.org ([2001:4830:134:3::10]:35300) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1emG3Z-00020A-Le for qemu-devel@nongnu.org; Thu, 15 Feb 2018 04:42:27 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1emG3Y-00007c-Ta for qemu-devel@nongnu.org; Thu, 15 Feb 2018 04:42:21 -0500 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:48156 helo=mx1.redhat.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1emG3V-00006B-HG; Thu, 15 Feb 2018 04:42:17 -0500 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.rdu2.redhat.com [10.11.54.6]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 1340B7D67B; Thu, 15 Feb 2018 09:42:17 +0000 (UTC) Received: from localhost (ovpn-116-159.ams2.redhat.com [10.36.116.159]) by smtp.corp.redhat.com (Postfix) with ESMTP id 6D1ED21411B6; Thu, 15 Feb 2018 09:42:16 +0000 (UTC) From: Stefan Hajnoczi To: Date: Thu, 15 Feb 2018 09:42:09 +0000 Message-Id: <20180215094210.27770-3-stefanha@redhat.com> In-Reply-To: <20180215094210.27770-1-stefanha@redhat.com> References: <20180215094210.27770-1-stefanha@redhat.com> X-Scanned-By: MIMEDefang 2.78 on 10.11.54.6 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.2]); Thu, 15 Feb 2018 09:42:17 +0000 (UTC) X-Greylist: inspected by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.2]); Thu, 15 Feb 2018 09:42:17 +0000 (UTC) for IP:'10.11.54.6' DOMAIN:'int-mx06.intmail.prod.int.rdu2.redhat.com' HELO:'smtp.corp.redhat.com' FROM:'stefanha@redhat.com' RCPT:'' X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 66.187.233.73 Subject: [Qemu-devel] [PULL v2 2/3] ratelimit: don't align wait time with slices X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Peter Maydell , Stefan Hajnoczi , qemu-block@nongnu.org, Wolfgang Bumiller Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: "Qemu-devel" From: Wolfgang Bumiller It is possible for rate limited writes to keep overshooting a slice's quota by a tiny amount causing the slice-aligned waiting period to effectively halve the rate. Signed-off-by: Wolfgang Bumiller Reviewed-by: Alberto Garcia Message-id: 20180207071758.6818-1-w.bumiller@proxmox.com Signed-off-by: Stefan Hajnoczi --- include/qemu/ratelimit.h | 11 +++++------ 1 file changed, 5 insertions(+), 6 deletions(-) diff --git a/include/qemu/ratelimit.h b/include/qemu/ratelimit.h index 8dece483f5..1b38291823 100644 --- a/include/qemu/ratelimit.h +++ b/include/qemu/ratelimit.h @@ -36,7 +36,7 @@ typedef struct { static inline int64_t ratelimit_calculate_delay(RateLimit *limit, uint64_t n) { int64_t now = qemu_clock_get_ns(QEMU_CLOCK_REALTIME); - uint64_t delay_slices; + double delay_slices; assert(limit->slice_quota && limit->slice_ns); @@ -55,12 +55,11 @@ static inline int64_t ratelimit_calculate_delay(RateLimit *limit, uint64_t n) return 0; } - /* Quota exceeded. Calculate the next time slice we may start - * sending data again. */ - delay_slices = (limit->dispatched + limit->slice_quota - 1) / - limit->slice_quota; + /* Quota exceeded. Wait based on the excess amount and then start a new + * slice. */ + delay_slices = (double)limit->dispatched / limit->slice_quota; limit->slice_end_time = limit->slice_start_time + - delay_slices * limit->slice_ns; + (uint64_t)(delay_slices * limit->slice_ns); return limit->slice_end_time - now; }