linux-kernel - Re: [PATCH v7 10/12] perf report: implement record trace decompression

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Date:   Wed, 13 Mar 2019 15:37:19 +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>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Andi Kleen <ak@...ux.intel.com>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v7 10/12] perf report: implement record trace
 decompression

On Tue, Mar 12, 2019 at 08:36:18AM +0300, Alexey Budankov wrote:

SBIP

> +#ifdef HAVE_ZSTD_SUPPORT
> +static int perf_session__process_compressed_event(struct perf_session *session,
> +					union perf_event *event, u64 file_offset)
> +{
> +	void *src;
> +	size_t decomp_size, src_size;
> +	u64 decomp_last_rem = 0;
> +	size_t decomp_len = session->header.env.comp_mmap_len;
> +	struct decomp *decomp, *decomp_last = session->decomp_last;
> +
> +	decomp = mmap(NULL, sizeof(struct decomp) + decomp_len, PROT_READ|PROT_WRITE,
> +		      MAP_ANONYMOUS|MAP_PRIVATE, -1, 0);
> +	if (decomp == MAP_FAILED) {
> +		pr_err("Couldn't allocate memory for decompression\n");
> +		return -1;
> +	}

ok, I see the need to keep this decomp around, we need the event
to be there the whole time, like the mmap for the standard events

we know the total uncompressed size when record is done, right?
could we save it in the COMPRESSED feature and alloc all the
needed uncompressed data in single mmap?

jirka