From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932537AbeCGKWB (ORCPT ); Wed, 7 Mar 2018 05:22:01 -0500 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:59464 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751142AbeCGKWA (ORCPT ); Wed, 7 Mar 2018 05:22:00 -0500 Date: Wed, 7 Mar 2018 11:21:57 +0100 From: Jiri Olsa To: Yisheng Xie Cc: acme@redhat.com, mingo@redhat.com, peterz@infradead.org, namhyung@kernel.org, alexander.shishkin@linux.intel.com, linux-kernel@vger.kernel.org, Kan Liang Subject: Re: [PATCH] perf mmap: Discard head in overwrite_rb_find_range Message-ID: <20180307102157.GC22848@krava> References: <1520336663-53466-1-git-send-email-xieyisheng1@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1520336663-53466-1-git-send-email-xieyisheng1@huawei.com> User-Agent: Mutt/1.9.1 (2017-09-22) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Mar 06, 2018 at 07:44:23PM +0800, 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. it conflicts a little with recent cleanup from Kan Liang,, https://marc.info/?t=152035082800001&r=1&w=2 otherwise it looks ok to me jirka > > Signed-off-by: Yisheng Xie > --- > 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 91531a7..6751ac9 100644 > --- a/tools/perf/util/mmap.c > +++ b/tools/perf/util/mmap.c > @@ -223,19 +223,18 @@ 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; > @@ -287,7 +286,7 @@ int perf_mmap__read_init(struct perf_mmap *md, bool overwrite, > * 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, startp, endp)) > + if (overwrite_rb_find_range(data, md->mask, startp, endp)) > return -EINVAL; > } > > -- > 1.7.12.4 >