From patchwork Mon Apr 5 12:45:35 2010 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Amit Shah X-Patchwork-Id: 49384 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Received: from lists.gnu.org (lists.gnu.org [199.232.76.165]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client did not present a certificate) by ozlabs.org (Postfix) with ESMTPS id D2A4AB7CF1 for ; Mon, 5 Apr 2010 23:03:26 +1000 (EST) Received: from localhost ([127.0.0.1]:57330 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1Nyln1-00013c-2q for incoming@patchwork.ozlabs.org; Mon, 05 Apr 2010 08:52:27 -0400 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1Nyli4-0000Ce-NG for qemu-devel@nongnu.org; Mon, 05 Apr 2010 08:47:20 -0400 Received: from [140.186.70.92] (port=47040 helo=eggs.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1Nyli3-0000C3-88 for qemu-devel@nongnu.org; Mon, 05 Apr 2010 08:47:20 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.69) (envelope-from ) id 1Nyli0-0007ez-HU for qemu-devel@nongnu.org; Mon, 05 Apr 2010 08:47:19 -0400 Received: from mx1.redhat.com ([209.132.183.28]:59735) by eggs.gnu.org with esmtp (Exim 4.69) (envelope-from ) id 1Nylhz-0007et-Sb for qemu-devel@nongnu.org; Mon, 05 Apr 2010 08:47:16 -0400 Received: from int-mx02.intmail.prod.int.phx2.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) by mx1.redhat.com (8.13.8/8.13.8) with ESMTP id o35ClE7d014849 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK); Mon, 5 Apr 2010 08:47:14 -0400 Received: from localhost (vpn-236-74.phx2.redhat.com [10.3.236.74]) by int-mx02.intmail.prod.int.phx2.redhat.com (8.13.8/8.13.8) with ESMTP id o35ClCms007732; Mon, 5 Apr 2010 08:47:13 -0400 From: Amit Shah To: qemu list Date: Mon, 5 Apr 2010 18:15:35 +0530 Message-Id: <1270471538-31275-3-git-send-email-amit.shah@redhat.com> In-Reply-To: <1270471538-31275-2-git-send-email-amit.shah@redhat.com> References: <1270471538-31275-1-git-send-email-amit.shah@redhat.com> <1270471538-31275-2-git-send-email-amit.shah@redhat.com> X-Scanned-By: MIMEDefang 2.67 on 10.5.11.12 X-detected-operating-system: by eggs.gnu.org: Genre and OS details not recognized. Cc: Amit Shah , Gerd Hoffmann , Juan Quintela Subject: [Qemu-devel] [PATCH 2/5] char: unix write: Add some sleep to ease off spinning in a tight loop X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org When the other end of a chardev connection isn't picking up data as fast as we're sending, we just used to keep spinning in a tight loop till all the data was sent out. Polling for POLLOUT indefinitely gives the other end a chance to catch up and also saves us CPU cycles. Signed-off-by: Amit Shah --- qemu-char.c | 17 +++++++++++++++-- 1 files changed, 15 insertions(+), 2 deletions(-) diff --git a/qemu-char.c b/qemu-char.c index d5b1662..48e1e57 100644 --- a/qemu-char.c +++ b/qemu-char.c @@ -36,6 +36,7 @@ #include #include +#include #include #include #include @@ -513,15 +514,27 @@ int send_all(int fd, const void *buf, size_t *len) static int unix_write(int fd, const uint8_t *buf, size_t *len) { + struct pollfd pollfds[1]; ssize_t tmplen, ret; + pollfds[0].fd = fd; + pollfds[0].events = POLLOUT; + tmplen = *len; *len = 0; while (tmplen > 0) { + ret = poll(pollfds, 1, -1); + if (ret == -1) { + if (errno == EINTR) { + continue; + } + return -1; + } ret = write(fd, buf, tmplen); if (ret < 0) { - if (errno != EINTR && errno != EAGAIN) - return -1; + if (errno != EINTR && errno != EAGAIN) { + return -1; + } } else if (ret == 0) { break; } else {