From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:36363) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1eleTj-0002Ja-1k for qemu-devel@nongnu.org; Tue, 13 Feb 2018 12:34:52 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1eleTe-0003EJ-UZ for qemu-devel@nongnu.org; Tue, 13 Feb 2018 12:34:51 -0500 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:38534 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 1eleTe-0003Du-Pe for qemu-devel@nongnu.org; Tue, 13 Feb 2018 12:34:46 -0500 From: Stefan Hajnoczi Date: Tue, 13 Feb 2018 17:34:28 +0000 Message-Id: <20180213173429.19501-5-stefanha@redhat.com> In-Reply-To: <20180213173429.19501-1-stefanha@redhat.com> References: <20180213173429.19501-1-stefanha@redhat.com> Subject: [Qemu-devel] [PATCH 4/5] ratelimit: don't align wait time with slices List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: Paolo Bonzini , Stefan Hajnoczi , Peter Maydell , Kevin Wolf , Wolfgang Bumiller 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; } -- 2.14.3