From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andreas Herrmann Subject: [PATCH v2 11/12] kvm tools: Modify term_putc to write more than one char Date: Mon, 19 May 2014 18:53:30 +0200 Message-ID: <1400518411-9759-12-git-send-email-andreas.herrmann@caviumnetworks.com> References: <1400518411-9759-1-git-send-email-andreas.herrmann@caviumnetworks.com> Mime-Version: 1.0 Content-Type: text/plain Cc: David Daney , Andreas Herrmann , , , James Hogan , David Daney To: Pekka Enberg Return-path: Received: from dns-bn1lp0143.outbound.protection.outlook.com ([207.46.163.143]:34309 "EHLO na01-bn1-obe.outbound.protection.outlook.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S932574AbaESQzd (ORCPT ); Mon, 19 May 2014 12:55:33 -0400 In-Reply-To: <1400518411-9759-1-git-send-email-andreas.herrmann@caviumnetworks.com> Sender: kvm-owner@vger.kernel.org List-ID: From: David Daney It is a performance enhancement. When running in a simulator, each system call to write a character takes a lot of time. Batching them up decreases the overhead (in the root kernel) of each virtio console write. Signed-off-by: David Daney Signed-off-by: Andreas Herrmann --- tools/kvm/term.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/tools/kvm/term.c b/tools/kvm/term.c index 3de410b..b153eed 100644 --- a/tools/kvm/term.c +++ b/tools/kvm/term.c @@ -52,11 +52,14 @@ int term_getc(struct kvm *kvm, int term) int term_putc(char *addr, int cnt, int term) { int ret; + int num_remaining = cnt; - while (cnt--) { - ret = write(term_fds[term][TERM_FD_OUT], addr++, 1); + while (num_remaining) { + ret = write(term_fds[term][TERM_FD_OUT], addr, num_remaining); if (ret < 0) return 0; + num_remaining -= ret; + addr += ret; } return cnt; -- 1.7.9.5