linux-kernel - Re: [PATCH v5 07/10] perf record: implement -z,--compression

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Date:   Tue, 5 Mar 2019 13:25:52 +0100
From:   Jiri Olsa <jolsa@...hat.com>
To:     Alexey Budankov <alexey.budankov@...ux.intel.com>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Andi Kleen <ak@...ux.intel.com>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v5 07/10] perf record: implement -z,--compression_level=n
 option and compression

On Fri, Mar 01, 2019 at 06:58:32PM +0300, Alexey Budankov wrote:

SNIP

> +static size_t record__zstd_compress(void *data, void *dst, size_t dst_size,
> +		void *src, size_t src_size)
> +{
> +	size_t compressed;
> +	struct perf_session *session = data;
> +	/* maximum size of record data size (2^16 - 1 - header) */
> +	const size_t max_record_size = (1 << 8 * sizeof(u16)) -

I dont follow this calculation, could you just use PERF_SAMPLE_MAX_SIZE?

jirka

> +					1 - sizeof(struct compressed_event);
> +

SNIP