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SubjectRe: [PATCH] perf mmap: Discard head in overwrite_rb_find_range
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Hi jirka,

On 2018/3/7 18:21, Jiri Olsa wrote:
> 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
>

I can send the next version based on Kan's patch after his patches are in the tree.

Thanks
Yisheng

> jirka
>
>>
>> Signed-off-by: Yisheng Xie <xieyisheng1@huawei.com>
>> ---
>> 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
>>
>
> .
>

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