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SubjectRe: [PATCH v12 2/3]: perf record: enable asynchronous trace writing
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On 11.10.2018 16:46, Jiri Olsa wrote:
> On Tue, Oct 09, 2018 at 11:58:53AM +0300, Alexey Budankov wrote:
>
> SNIP
>
>> +#ifdef HAVE_AIO_SUPPORT
>> +int perf_mmap__aio_push(struct perf_mmap *md, void *to,
>> + int push(void *to, struct aiocb *cblock, void *buf, size_t size, off_t off),
>> + off_t *off)
>> +{
>> + u64 head = perf_mmap__read_head(md);
>> + unsigned char *data = md->base + page_size;
>> + unsigned long size, size0 = 0;
>> + void *buf;
>> + int rc = 0;
>> +
>> + rc = perf_mmap__read_init(md);
>> + if (rc < 0)
>> + return (rc == -EAGAIN) ? 0 : -1;
>> +
>> + /*
>> + * md->base data is copied into md->data buffer to
>> + * release space in the kernel buffer as fast as possible,
>> + * thru perf_mmap__consume() below.
>> + *
>> + * That lets the kernel to proceed with storing more
>> + * profiling data into the kernel buffer earlier than other
>> + * per-cpu kernel buffers are handled.
>> + *
>> + * Coping can be done in two steps in case the chunk of
>> + * profiling data crosses the upper bound of the kernel buffer.
>> + * In this case we first move part of data from md->start
>> + * till the upper bound and then the reminder from the
>> + * beginning of the kernel buffer till the end of
>> + * the data chunk.
>> + */
>> +
>> + size = md->end - md->start;
>> +
>> + if ((md->start & md->mask) + size != (md->end & md->mask)) {
>> + buf = &data[md->start & md->mask];
>> + size = md->mask + 1 - (md->start & md->mask);
>> + md->start += size;
>> + memcpy(md->aio.data, buf, size);
>> + size0 = size;
>> + }
>> +
>> + buf = &data[md->start & md->mask];
>> + size = md->end - md->start;
>> + md->start += size;
>> + memcpy(md->aio.data + size0, buf, size);
>> +
>> + /*
>> + * Increment md->refcount to guard md->data buffer
>> + * from premature deallocation because md object can be
>> + * released earlier than aio write request started
>> + * on mmap->data is complete.
>> + *
>> + * perf_mmap__put() is done at record__aio_complete()
>> + * after started request completion.
>> + */
>> + perf_mmap__get(md);
>> +
>> + md->prev = head;
>> + perf_mmap__consume(md);
>> +
>> + rc = push(to, &(md->aio.cblock), md->aio.data, size0 + size, *off);
>> + if (!rc) {
>> + *off += size0 + size;
>> + } else {
>> + /*
>> + * Decrement md->refcount back if aio write
>> + * operation failed to start.
>> + */
>> + perf_mmap__put(md);
>> + }
>> +
>> + return rc;
>> +}
>> +#else
>> +int perf_mmap__aio_push(struct perf_mmap *md __maybe_unused, void *to __maybe_unused,
>> + int push(void *to, struct aiocb *cblock, void *buf, size_t size, off_t off) __maybe_unused,
>> + off_t *off __maybe_unused)
>> +{
>> + return 0;
>> +}
>
> I think you need to put this one in the header as static inline
> otherwise it'd still appear in the NO_AIO=1 build, like:
> [jolsa@krava perf]$ make NO_AIO=1
> ...
> [jolsa@krava perf]$ nm -D perf | grep perf_mmap__aio_push
> 00000000004c2be0 T perf_mmap__aio_push
>
> change below makes it disappear completely>
> jirka
>
>
> ---
> diff --git a/tools/perf/util/mmap.c b/tools/perf/util/mmap.c
> index b176d88b3fcb..8c7516696891 100644
> --- a/tools/perf/util/mmap.c
> +++ b/tools/perf/util/mmap.c
> @@ -445,13 +445,6 @@ int perf_mmap__aio_push(struct perf_mmap *md, void *to,
>
> return rc;
> }
> -#else
> -int perf_mmap__aio_push(struct perf_mmap *md __maybe_unused, void *to __maybe_unused,
> - int push(void *to, struct aiocb *cblock, void *buf, size_t size, off_t off) __maybe_unused,
> - off_t *off __maybe_unused)
> -{
> - return 0;
> -}
> #endif
>
> /*
> diff --git a/tools/perf/util/mmap.h b/tools/perf/util/mmap.h
> index 04ff4d2ffdbe..3ccf8c925002 100644
> --- a/tools/perf/util/mmap.h
> +++ b/tools/perf/util/mmap.h
> @@ -105,10 +105,21 @@ union perf_event *perf_mmap__read_event(struct perf_mmap *map);
>
> int perf_mmap__push(struct perf_mmap *md, void *to,
> int push(struct perf_mmap *map, void *to, void *buf, size_t size));
> +
> +#ifdef HAVE_AIO_SUPPORT
> int perf_mmap__aio_push(struct perf_mmap *md, void *to,
> int push(void *to, struct aiocb *cblock, void *buf, size_t size, off_t off),
> off_t *off);
>
> +#else
> +static inline int perf_mmap__aio_push(struct perf_mmap *md __maybe_unused, void *to __maybe_unused,
> + int push(void *to, struct aiocb *cblock, void *buf, size_t size, off_t off) __maybe_unused,
> + off_t *off __maybe_unused)
> +{
> + return 0;
> +}
> +#endif
> +
> size_t perf_mmap__mmap_len(struct perf_mmap *map);
>
> int perf_mmap__read_init(struct perf_mmap *md);
>

Accepted.

Thanks,
Alexey

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