From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755338Ab0ASHgE (ORCPT ); Tue, 19 Jan 2010 02:36:04 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754991Ab0ASHf5 (ORCPT ); Tue, 19 Jan 2010 02:35:57 -0500 Received: from cn.fujitsu.com ([222.73.24.84]:63027 "EHLO song.cn.fujitsu.com" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1755339Ab0ASHfz (ORCPT ); Tue, 19 Jan 2010 02:35:55 -0500 Message-ID: <4B556086.7000909@cn.fujitsu.com> Date: Tue, 19 Jan 2010 15:34:30 +0800 From: Lai Jiangshan User-Agent: Thunderbird 2.0.0.6 (Windows/20070728) MIME-Version: 1.0 To: Steven Rostedt , linux-kernel@vger.kernel.org, Ingo Molnar , Andrew Morton , Frederic Weisbecker Subject: [PATCH 6/6] tracing: Write directly into splice page for trace_pipe Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Steven Rostedt Now that the trace_seq has a separate buffer space, we can use this feature to write directly into the splice page, instead of writing to the trace_seq buffer and then copying it. This has shown almost a 4% improvement in reading trace_pipe via splice: Average timing of reading 10megs from trace_pipe before patch: real 0m1.619s user 0m0.002s sys 0m1.596s After patch: real 0m1.561s user 0m0.002s sys 0m1.535s These were the average of five runs of reading 10megs. Signed-off-by: Steven Rostedt Signed-off-by: Lai Jiangshan --- diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 74ad344..0030d4b 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -544,25 +544,6 @@ ssize_t trace_seq_to_user(struct trace_seq *s, char __user *ubuf, size_t cnt) return cnt; } -static ssize_t trace_seq_to_buffer(struct trace_seq *s, void *buf, size_t cnt) -{ - int len; - void *ret; - - if (s->len <= s->readpos) - return -EBUSY; - - len = s->len - s->readpos; - if (cnt > len) - cnt = len; - ret = memcpy(buf, s->buffer + s->readpos, cnt); - if (!ret) - return -EFAULT; - - s->readpos += cnt; - return cnt; -} - /* * ftrace_max_lock is used to protect the swapping of buffers * when taking a max snapshot. The buffers themselves are @@ -3280,21 +3261,18 @@ static ssize_t tracing_splice_read_pipe(struct file *filp, if (!pages[i]) break; - rem = tracing_fill_pipe_page(rem, iter); + trace_seq_init(&iter->seq, page_address(pages[i]), PAGE_SIZE); - /* Copy the data into the page, so we can start over. */ - ret = trace_seq_to_buffer(&iter->seq, - page_address(pages[i]), - iter->seq.len); - if (ret < 0) { + rem = tracing_fill_pipe_page(rem, iter); + if (!iter->seq.len) { __free_page(pages[i]); break; } + partial[i].offset = 0; partial[i].len = iter->seq.len; - - trace_seq_reset(&iter->seq); } + trace_seq_init(&iter->seq, iter->buffer, FTRACE_SEQ_BUFSIZE); trace_access_unlock(iter->cpu_file); trace_event_read_unlock();