Re: [PATCH 5/6] perf session: Move map/unmap into reader__mmap function

[Jiri Olsa <jolsa@redhat.com>]

On Wed, Sep 29, 2021 at 11:41:53AM +0300, Alexey Bayduraev wrote:
> Moving mapping and unmapping code into reader__mmap, so the mmap
> code is located together. Moving head/file_offset computation into
> reader__mmap function, so all the offset computation is located
> together and in one place only.
> 
> Suggested-by: Jiri Olsa <jolsa@kernel.org>
> Acked-by: Namhyung Kim <namhyung@gmail.com>
> Reviewed-by: Riccardo Mancini <rickyman7@gmail.com>
> Tested-by: Riccardo Mancini <rickyman7@gmail.com>
> Signed-off-by: Alexey Bayduraev <alexey.v.bayduraev@linux.intel.com>
> ---
>  tools/perf/util/session.c | 60 +++++++++++++++++++++++----------------
>  1 file changed, 35 insertions(+), 25 deletions(-)
> 
> diff --git a/tools/perf/util/session.c b/tools/perf/util/session.c
> index 85142d2a9a5a..5e08def72b41 100644
> --- a/tools/perf/util/session.c
> +++ b/tools/perf/util/session.c
> @@ -2206,12 +2206,9 @@ static int
>  reader__init(struct reader *rd, bool *one_mmap)
>  {
>  	struct reader_state *st = &rd->state;
> -	u64 page_offset;
>  	char **mmaps = st->mmaps;
>  
> -	page_offset = page_size * (rd->data_offset / page_size);
> -	st->file_offset = page_offset;
> -	st->head = rd->data_offset - page_offset;
> +	st->head = rd->data_offset;
>  

extra line, please remove

jirka

>  	st->data_size = rd->data_size + rd->data_offset;
>  
> @@ -2238,15 +2235,12 @@ reader__exit(struct reader *rd)
>  }
>  
>  static int
> -reader__process_events(struct reader *rd, struct perf_session *session,
> -		       struct ui_progress *prog)
> +reader__mmap(struct reader *rd, struct perf_session *session)
>  {
>  	struct reader_state *st = &rd->state;
> -	u64 page_offset, size;
> -	int err = 0, mmap_prot, mmap_flags;
> +	int mmap_prot, mmap_flags;
>  	char *buf, **mmaps = st->mmaps;
> -	union perf_event *event;
> -	s64 skip;
> +	u64 page_offset;
>  
>  	mmap_prot  = PROT_READ;
>  	mmap_flags = MAP_SHARED;
> @@ -2257,20 +2251,45 @@ reader__process_events(struct reader *rd, struct perf_session *session,
>  		mmap_prot  |= PROT_WRITE;
>  		mmap_flags = MAP_PRIVATE;
>  	}
> -remap:
> +
> +	if (mmaps[st->mmap_idx]) {
> +		munmap(mmaps[st->mmap_idx], st->mmap_size);
> +		mmaps[st->mmap_idx] = NULL;
> +	}
> +
> +	page_offset = page_size * (st->head / page_size);
> +	st->file_offset += page_offset;
> +	st->head -= page_offset;
> +
>  	buf = mmap(NULL, st->mmap_size, mmap_prot, mmap_flags, rd->fd,
>  		   st->file_offset);
>  	if (buf == MAP_FAILED) {
>  		pr_err("failed to mmap file\n");
> -		err = -errno;
> -		goto out;
> +		return -errno;
>  	}
>  	mmaps[st->mmap_idx] = st->mmap_cur = buf;
>  	st->mmap_idx = (st->mmap_idx + 1) & (ARRAY_SIZE(st->mmaps) - 1);
>  	st->file_pos = st->file_offset + st->head;
> +	return 0;
> +}
> +
> +static int
> +reader__process_events(struct reader *rd, struct perf_session *session,
> +		       struct ui_progress *prog)
> +{
> +	struct reader_state *st = &rd->state;
> +	u64 size;
> +	int err = 0;
> +	union perf_event *event;
> +	s64 skip;
> +
> +remap:
> +	err = reader__mmap(rd, session);
> +	if (err)
> +		goto out;
>  	if (session->one_mmap) {
> -		session->one_mmap_addr = buf;
> -		session->one_mmap_offset = st->file_offset;
> +		session->one_mmap_addr   = rd->state.mmap_cur;
> +		session->one_mmap_offset = rd->state.file_offset;
>  	}
>  
>  more:
> @@ -2279,17 +2298,8 @@ reader__process_events(struct reader *rd, struct perf_session *session,
>  	if (IS_ERR(event))
>  		return PTR_ERR(event);
>  
> -	if (!event) {
> -		if (mmaps[st->mmap_idx]) {
> -			munmap(mmaps[st->mmap_idx], st->mmap_size);
> -			mmaps[st->mmap_idx] = NULL;
> -		}
> -
> -		page_offset = page_size * (st->head / page_size);
> -		st->file_offset += page_offset;
> -		st->head -= page_offset;
> +	if (!event)
>  		goto remap;
> -	}
>  
>  	session->active_reader = rd;
>  	size = event->header.size;
> -- 
> 2.19.0
>