linux-kernel - Re: [PATCH v10 09/12] perf record: implement -z,--compression

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Date:   Tue, 14 May 2019 18:46:31 -0300
From:   Arnaldo Carvalho de Melo <arnaldo.melo@...il.com>
To:     Alexey Budankov <alexey.budankov@...ux.intel.com>
Cc:     Jiri Olsa <jolsa@...hat.com>, 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 v10 09/12] perf record: implement
 -z,--compression_level[=<n>] option

Em Tue, May 14, 2019 at 05:20:41PM -0300, Arnaldo Carvalho de Melo escreveu:
> Em Mon, Mar 18, 2019 at 08:44:42PM +0300, Alexey Budankov escreveu:
> > 
> > Implemented -z,--compression_level[=<n>] option that enables compression
> > of mmaped kernel data buffers content in runtime during perf record
> > mode collection. Default option value is 1 (fastest compression).

<SNIP>
 
> [root@...co ~]# perf record -z2
> ^C[ perf record: Woken up 1 times to write data ]
> 0x1746e0 [0x76]: failed to process type: 81 [Invalid argument]
> [ perf record: Captured and wrote 1.568 MB perf.data, compressed (original 0.452 MB, ratio is 3.995) ]
> 
> [root@...co ~]#

So, its the buildid processing at the end, so we can't do build-id
processing when using PERF_RECORD_COMPRESSED, otherwise we'd have to
uncompress at the end to find the PERF_RECORD_FORK/PERF_RECORD_MMAP,
etc.

[root@...co ~]# perf record -z2  --no-buildid sleep 1
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.020 MB perf.data, compressed (original 0.001 MB, ratio is 2.153) ]
[root@...co ~]# perf report -D | grep PERF_RECORD_COMP
0x4f40 [0x195]: failed to process type: 81 [Invalid argument]
Error:
failed to process sample
0 0x4f40 [0x195]: PERF_RECORD_COMPRESSED
[root@...co ~]#

I'll play with it tomorrow.

- Arnaldo
 
> I've pushed what I have to the tmp.perf/core branch, please try to see
> if I made any mistake in fixing up conflicts with BPF_PROG_INFO and
> BPF_BTF header features. I'll continue tomorrow with 10-12/12.