Re: [PATCH v2 10/13] perf header: add a buffer to struct feat_fd

[Jiri Olsa]

On Tue, May 23, 2017 at 12:48:50AM -0700, David Carrillo-Cisneros wrote:

SNIP

> @@ -795,11 +831,19 @@ static int write_pmu_mappings(struct feat_fd *fd,
>  			      struct perf_evlist *evlist __maybe_unused)
>  {
>  	struct perf_pmu *pmu = NULL;
> -	off_t offset = lseek(fd->fd, 0, SEEK_CUR);
> -	__u32 pmu_num = 0;
> +	u32 pmu_num = 0;
>  	int ret;
>  
> -	/* write real pmu_num later */
> +	/*
> +	 * Do a first pass to count number of pmu to avoid lseek so this
> +	 * works in pipe mode as well.
> +	 */
> +	while ((pmu = perf_pmu__scan(pmu))) {
> +		if (!pmu->name)
> +			continue;
> +		pmu_num++;
> +	}

please put this functionality into preceeding separate patch

thanks,
jirka