From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:42563) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YZurP-0003kE-RZ for qemu-devel@nongnu.org; Mon, 23 Mar 2015 01:25:15 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1YZurL-0004kt-DA for qemu-devel@nongnu.org; Mon, 23 Mar 2015 01:25:11 -0400 Received: from mx1.redhat.com ([209.132.183.28]:44250) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YZurL-0004iv-56 for qemu-devel@nongnu.org; Mon, 23 Mar 2015 01:25:07 -0400 From: Fam Zheng Date: Mon, 23 Mar 2015 13:24:15 +0800 Message-Id: <1427088255-29885-1-git-send-email-famz@redhat.com> Subject: [Qemu-devel] [PATCH v2] block: Switch to host monotonic clock for IO throttling List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: Kevin Wolf , pbonzini@redhat.com, berto@igalia.com, Stefan Hajnoczi Currently, throttle timers won't make any progress when VCPU is not running, which would stall the request queue in utils, qtest, vm suspending, and live migration without special handling. For example in bdrv_drain_all, all requests are resumed immediately without taking throttling limit into account. This means whenever it is called, IO throttling goes ineffective (examples: system reset, migration and many block job operations.). This might be some loophole that guest could exploit. If we use the host clock, we can later just trust the nested poll when waiting for requests. Note that for qemu-iotests case 093, which sets up qtest when running QEMU, we still use vm clock so the script can control the clock stepping in order to be deterministic. Signed-off-by: Fam Zheng --- v2: Don't break qemu-iotests 093. --- block.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/block.c b/block.c index 0fe97de..89a1d5b 100644 --- a/block.c +++ b/block.c @@ -30,6 +30,7 @@ #include "qapi/qmp/qjson.h" #include "sysemu/block-backend.h" #include "sysemu/sysemu.h" +#include "sysemu/qtest.h" #include "qemu/notify.h" #include "block/coroutine.h" #include "block/qapi.h" @@ -181,10 +182,16 @@ static void bdrv_throttle_write_timer_cb(void *opaque) /* should be called before bdrv_set_io_limits if a limit is set */ void bdrv_io_limits_enable(BlockDriverState *bs) { + int clock_type = QEMU_CLOCK_REALTIME; + + if (qtest_enabled()) { + /* For testing block IO throttling only */ + clock_type = QEMU_CLOCK_VIRTUAL; + } assert(!bs->io_limits_enabled); throttle_init(&bs->throttle_state, bdrv_get_aio_context(bs), - QEMU_CLOCK_VIRTUAL, + clock_type, bdrv_throttle_read_timer_cb, bdrv_throttle_write_timer_cb, bs); -- 1.9.3