From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:56609) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cCO2L-0005h1-QV for qemu-devel@nongnu.org; Thu, 01 Dec 2016 04:52:18 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1cCO2L-0005Kh-0R for qemu-devel@nongnu.org; Thu, 01 Dec 2016 04:52:17 -0500 Date: Thu, 1 Dec 2016 17:52:07 +0800 From: Fam Zheng Message-ID: <20161201095207.GB28711@lemon> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Subject: Re: [Qemu-devel] QEMU 1.1.2: block IO throttle might occasionally freeze running process's IO to zero List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Bob Chen Cc: qemu-block@nongnu.org, qemu-devel@nongnu.org On Thu, 12/01 12:07, Bob Chen wrote: > Test case: > > 1. QEMU 1.1.2 > 2. Run fio inside the vm, give it some pressure. Watch the realtime > throughput > 3. block_set_io_throttle drive_2 100000000 0 0 2000 0 0 # throttle > bps and iops, any value > 4. Observed that the IO is very likely to freeze to zero. The fio process > stuck! > 5. Kill the former fio process, start a new one. The IO turns back to normal > > Didn't reproduce it with QEMU 2.5. > > > Actually I'm not wishfully thinking the community would help fix this bug > on such an ancient version. Just hope someone can tell me what is the root > cause. Then I have to evaluate whether I should move to higher version > QEMU, or fix this bug on 1.1.2 in-place(if it is a small one). The throttling implementation is completely refreshed so I think it's not easy to suggest a root cause for you. Fam