From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:60292) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1SRlnC-0002Bm-4o for qemu-devel@nongnu.org; Tue, 08 May 2012 10:53:40 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1SRln5-00081J-OL for qemu-devel@nongnu.org; Tue, 08 May 2012 10:53:33 -0400 Received: from mail-pz0-f47.google.com ([209.85.210.47]:52083) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1SRln5-0007Sn-Ct for qemu-devel@nongnu.org; Tue, 08 May 2012 10:53:27 -0400 Received: by mail-pz0-f47.google.com with SMTP id h21so8313251dal.34 for ; Tue, 08 May 2012 07:53:26 -0700 (PDT) Sender: Paolo Bonzini From: Paolo Bonzini Date: Tue, 8 May 2012 16:51:57 +0200 Message-Id: <1336488722-13120-18-git-send-email-pbonzini@redhat.com> In-Reply-To: <1336488722-13120-1-git-send-email-pbonzini@redhat.com> References: <1336488722-13120-1-git-send-email-pbonzini@redhat.com> Subject: [Qemu-devel] [PATCH 1.1 17/22] stream: fix ratelimiting corner case List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: kwolf@redhat.com, stefanha@linux.vnet.ibm.com This fixes inability to make progress in streaming if the quota is set to less than the amount of data that an I/O operation has to write. In this case, limit->dispatched + n will always be above the quota and, due to the "goto retry" to recheck cancellation and allocation, streaming will livelock. This can be reproduced with "block_job_set_speed ide0-hd0 1b". Of course, with this patch the requested limit will not be obeyed. That could be done with another patch that caps is_allocated's n argument by the slice quota. Signed-off-by: Paolo Bonzini --- block/stream.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) diff --git a/block/stream.c b/block/stream.c index 25f98e4..a2c8f67 100644 --- a/block/stream.c +++ b/block/stream.c @@ -33,19 +33,19 @@ typedef struct { static int64_t ratelimit_calculate_delay(RateLimit *limit, uint64_t n) { - int64_t delay_ns = 0; int64_t now = qemu_get_clock_ns(rt_clock); if (limit->next_slice_time < now) { limit->next_slice_time = now + SLICE_TIME; limit->dispatched = 0; } - if (limit->dispatched + n > limit->slice_quota) { - delay_ns = limit->next_slice_time - now; - } else { + if (limit->dispatched == 0 || limit->dispatched + n <= limit->slice_quota) { limit->dispatched += n; + return 0; + } else { + limit->dispatched = n; + return limit->next_slice_time - now; } - return delay_ns; } static void ratelimit_set_speed(RateLimit *limit, uint64_t speed) -- 1.7.10.1