From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752844AbeCPOQ6 (ORCPT ); Fri, 16 Mar 2018 10:16:58 -0400 Received: from mga09.intel.com ([134.134.136.24]:65129 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751582AbeCPOQz (ORCPT ); Fri, 16 Mar 2018 10:16:55 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.48,316,1517904000"; d="scan'208";a="208821594" Subject: Re: [PATCH v2 -perf/core 1/2] perf mmap: Discard head in overwrite_rb_find_range To: Yisheng Xie , acme@redhat.com Cc: mingo@redhat.com, peterz@infradead.org, namhyung@kernel.org, jolsa@redhat.com, alexander.shishkin@linux.intel.com, linux-kernel@vger.kernel.org References: <1520944274-37001-1-git-send-email-xieyisheng1@huawei.com> From: "Liang, Kan" Message-ID: Date: Fri, 16 Mar 2018 10:16:53 -0400 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.6.0 MIME-Version: 1.0 In-Reply-To: <1520944274-37001-1-git-send-email-xieyisheng1@huawei.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 3/13/2018 8:31 AM, Yisheng Xie wrote: > In overwrite mode, start will be set to head in perf_mmap__read_init. > Therefore, it is no need to set the start one more in > overwrite_rb_find_range and *start can be used as head instead of > passing head to overwrite_rb_find_range. > Looks good to me. Reviewed-by: Kan Liang Thanks, Kan > Signed-off-by: Yisheng Xie > --- > v2: > - rebase to perf/core > > tools/perf/util/mmap.c | 15 +++++++-------- > 1 file changed, 7 insertions(+), 8 deletions(-) > > diff --git a/tools/perf/util/mmap.c b/tools/perf/util/mmap.c > index 074c4fd..38ca3ff 100644 > --- a/tools/perf/util/mmap.c > +++ b/tools/perf/util/mmap.c > @@ -199,19 +199,18 @@ int perf_mmap__mmap(struct perf_mmap *map, struct mmap_params *mp, int fd) > return 0; > } > > -static int overwrite_rb_find_range(void *buf, int mask, u64 head, u64 *start, u64 *end) > +static int overwrite_rb_find_range(void *buf, int mask, u64 *start, u64 *end) > { > struct perf_event_header *pheader; > - u64 evt_head = head; > + u64 evt_head = *start; > int size = mask + 1; > > - pr_debug2("overwrite_rb_find_range: buf=%p, head=%"PRIx64"\n", buf, head); > - pheader = (struct perf_event_header *)(buf + (head & mask)); > - *start = head; > + pr_debug2("%s: buf=%p, start=%"PRIx64"\n", __func__, buf, *start); > + pheader = (struct perf_event_header *)(buf + (*start & mask)); > while (true) { > - if (evt_head - head >= (unsigned int)size) { > + if (evt_head - *start >= (unsigned int)size) { > pr_debug("Finished reading overwrite ring buffer: rewind\n"); > - if (evt_head - head > (unsigned int)size) > + if (evt_head - *start > (unsigned int)size) > evt_head -= pheader->size; > *end = evt_head; > return 0; > @@ -262,7 +261,7 @@ int perf_mmap__read_init(struct perf_mmap *md) > * Backward ring buffer is full. We still have a chance to read > * most of data from it. > */ > - if (overwrite_rb_find_range(data, md->mask, head, &md->start, &md->end)) > + if (overwrite_rb_find_range(data, md->mask, &md->start, &md->end)) > return -EINVAL; > } > >