From: "Wangnan (F)" <wangnan0@huawei.com>
To: Jiri Olsa <jolsa@redhat.com>
Cc: <acme@kernel.org>, <lizefan@huawei.com>,
<linux-kernel@vger.kernel.org>, <pi3orama@163.com>,
Arnaldo Carvalho de Melo <acme@redhat.com>,
He Kuang <hekuang@huawei.com>, Jiri Olsa <jolsa@kernel.org>,
Masami Hiramatsu <mhiramat@kernel.org>,
Namhyung Kim <namhyung@kernel.org>,
Nilay Vaish <nilayvaish@gmail.com>
Subject: Re: [PATCH v15 03/12] perf tools: Update perf evlist mmap related APIs and helpers
Date: Thu, 14 Jul 2016 09:58:09 +0800 [thread overview]
Message-ID: <5786F1B1.40307@huawei.com> (raw)
In-Reply-To: <20160713140637.GB31742@krava>
On 2016/7/13 22:06, Jiri Olsa wrote:
> On Tue, Jul 12, 2016 at 10:00:03AM +0000, Wang Nan wrote:
>
> SNIP
>
>> -union perf_event *perf_evlist__mmap_read_forward(struct perf_evlist *evlist, int idx)
>> +union perf_event *perf_mmap__read_forward(struct perf_mmap *md, bool overwrite)
>> {
>> - struct perf_mmap *md = &evlist->mmap[idx];
>> u64 head;
>> u64 old = md->prev;
>>
>> @@ -795,13 +795,12 @@ union perf_event *perf_evlist__mmap_read_forward(struct perf_evlist *evlist, int
>>
>> head = perf_mmap__read_head(md);
>>
>> - return perf_mmap__read(md, evlist->overwrite, old, head, &md->prev);
>> + return perf_mmap__read(md, overwrite, old, head, &md->prev);
>> }
>>
>> union perf_event *
>> -perf_evlist__mmap_read_backward(struct perf_evlist *evlist, int idx)
>> +perf_mmap__read_backward(struct perf_mmap *md, bool overwrite __maybe_unused)
>> {
>> - struct perf_mmap *md = &evlist->mmap[idx];
>> u64 head, end;
>> u64 start = md->prev;
>>
>> @@ -836,6 +835,20 @@ perf_evlist__mmap_read_backward(struct perf_evlist *evlist, int idx)
>> return perf_mmap__read(md, false, start, end, &md->prev);
> should you pas evlist->overwrite in here?
No need. The second arg of perf_mmap__read() is not 'overwrite', but
'check_messup'.
When set to 'true', stop reading if caller require a buffer larger than
half of the
size of the ring buffer and report a warning. Only forward, read-only
ring buffer
requires this check. We can always read the whole backward ring buffer
because we
pause it before reading.
I'll add more comments here.
Thank you.
> thanks,
> jirka
next prev parent reply other threads:[~2016-07-14 1:58 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-07-12 10:00 [PATCH v15 00/12] perf tools: Support overwritable ring buffer Wang Nan
2016-07-12 10:00 ` [PATCH v15 01/12] perf tools: Drop redundant evsel->overwrite indicator Wang Nan
2016-07-12 10:00 ` [PATCH v15 02/12] tools lib fd array: Allow associating a pointer cookie with each entry Wang Nan
2016-07-12 10:00 ` [PATCH v15 03/12] perf tools: Update perf evlist mmap related APIs and helpers Wang Nan
2016-07-13 14:06 ` Jiri Olsa
2016-07-14 1:58 ` Wangnan (F) [this message]
2016-07-12 10:00 ` [PATCH v15 04/12] perf tools: Record mmap cookie into fdarray private field Wang Nan
2016-07-12 10:00 ` [PATCH v15 05/12] perf tools: Extract common code in mmap failure processing Wang Nan
2016-07-12 10:00 ` [PATCH v15 06/12] perf tools: Alloc backward_mmap array for evlist Wang Nan
2016-07-12 10:00 ` [PATCH v15 07/12] perf tools: Map backward events to backward_mmap Wang Nan
2016-07-13 14:06 ` Jiri Olsa
2016-07-12 10:00 ` [PATCH v15 08/12] perf tools: Drop evlist->backward Wang Nan
2016-07-12 10:00 ` [PATCH v15 09/12] perf record: Read from overwritable ring buffer Wang Nan
2016-07-13 14:06 ` Jiri Olsa
2016-07-13 14:07 ` Jiri Olsa
2016-07-13 14:07 ` Jiri Olsa
2016-07-12 10:00 ` [PATCH v15 10/12] perf tools: Enable overwrite settings Wang Nan
2016-07-12 10:00 ` [PATCH v15 11/12] perf tools: Don't warn about out of order event if write_backward is used Wang Nan
2016-07-12 10:00 ` [PATCH v15 12/12] perf tools: Add --tail-synthesize option Wang Nan
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