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SubjectRe: [PATCH v4 0/10] perf: enable compression of record mode trace to save storage space
On Thu, Feb 28, 2019 at 11:35:24AM +0300, Alexey Budankov wrote:
>
> The patch set implements runtime trace compression (-z option) in
> record mode and trace auto decompression in report and inject modes.
> Streaming Zstandard (Zstd) API (zstd) is used for compression and
> decompression of data that come from kernel mmaped data buffers.
>
> Usage of implemented -z,--compression_level=n option provides ~3-5x
> avg. trace file size reduction on variety of tested workloads what
> saves storage space on larger server systems where trace file size
> can easily reach several tens or even hundreds of GiBs, especially
> when profiling with dwarf-based stacks and tracing of context switches.
> Implemented -f,--mmap-flush option can be used to avoid compressing
> every single byte of data and increase compression ratio at the same
> time lowering tool runtime overhead. Default option value is 1 what
> is equal to the current perf record implementation. The option is
> independent from -z setting and doesn't vary with compression level:
>
> $ tools/perf/perf record -z 1 -e cycles -- matrix.gcc
> $ tools/perf/perf record --aio=1 -z 1 -e cycles -- matrix.gcc
> $ tools/perf/perf record -z 1 -f 1024 -e cycles -- matrix.gcc
> $ tools/perf/perf record --aio=1 -z 1 -f 1024 -e cycles -- matrix.gcc

please make the 'z' option to choose some default value,
so it's possible just to run:

perf record -z ...

to get comrpessed data.. not sure which strategy to use,
probably the fastest '-z 1' as default

with some warning about using that default value perhaps

jirka

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