From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:50725) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ezPpF-0002Za-Q9 for qemu-devel@nongnu.org; Fri, 23 Mar 2018 12:45:58 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ezPpE-00059l-TM for qemu-devel@nongnu.org; Fri, 23 Mar 2018 12:45:57 -0400 Date: Fri, 23 Mar 2018 16:45:45 +0000 From: "Dr. David Alan Gilbert" Message-ID: <20180323164545.GC17165@work-vm> References: <1520507908-16743-1-git-send-email-pl@kamp.de> <1520507908-16743-5-git-send-email-pl@kamp.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1520507908-16743-5-git-send-email-pl@kamp.de> Subject: Re: [Qemu-devel] [PATCH 4/5] migration/block: limit the number of parallel I/O requests List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Peter Lieven Cc: qemu-devel@nongnu.org, qemu-block@nongnu.org, quintela@redhat.com, famz@redhat.com, stefanha@redhat.com, jjherne@linux.vnet.ibm.com * Peter Lieven (pl@kamp.de) wrote: > the current implementation submits up to 512 I/O requests in parallel > which is much to high especially for a background task. > This patch adds a maximum limit of 16 I/O requests that can > be submitted in parallel to avoid monopolizing the I/O device. > > Signed-off-by: Peter Lieven Queued (including 5/5) > --- > migration/block.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/migration/block.c b/migration/block.c > index 41b95d1..ce939e2 100644 > --- a/migration/block.c > +++ b/migration/block.c > @@ -37,6 +37,7 @@ > #define MAX_IS_ALLOCATED_SEARCH (65536 * BDRV_SECTOR_SIZE) > > #define MAX_IO_BUFFERS 512 > +#define MAX_PARALLEL_IO 16 > > //#define DEBUG_BLK_MIGRATION > > @@ -775,6 +776,7 @@ static int block_save_iterate(QEMUFile *f, void *opaque) > while ((block_mig_state.submitted + > block_mig_state.read_done) * BLOCK_SIZE < > qemu_file_get_rate_limit(f) && > + block_mig_state.submitted < MAX_PARALLEL_IO && > (block_mig_state.submitted + block_mig_state.read_done) < > MAX_IO_BUFFERS) { > blk_mig_unlock(); > -- > 2.7.4 > > > -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK