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Merge pull request #2299 from senhuang42/env_var_num_threads

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Allow environment variable to specify number of threads for compression
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Yann Collet
2020-09-14 14:04:19 -07:00
committed by GitHub
parent 517956e67d a71963c7b8
commit e583e0be8c
4 changed files with 59 additions and 8 deletions
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programs/zstd.1.md
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@@ -271,11 +271,20 @@ the last one takes effect.
Using environment variables to set parameters has security implications.
Therefore, this avenue is intentionally restricted.
Only `ZSTD_CLEVEL` is supported currently, for setting compression level.
Only `ZSTD_CLEVEL` and `ZSTD_NBTHREADS` are currently supported.
They set the compression level and number of threads to use during compression, respectively.
`ZSTD_CLEVEL` can be used to set the level between 1 and 19 (the "normal" range).
If the value of `ZSTD_CLEVEL` is not a valid integer, it will be ignored with a warning message.
`ZSTD_CLEVEL` just replaces the default compression level (`3`).
It can be overridden by corresponding command line arguments.
`ZSTD_NBTHREADS` can be used to set the number of threads `zstd` will attempt to use during compression.
If the value of `ZSTD_NBTHREADS` is not a valid unsigned integer, it will be ignored with a warning message.
'ZSTD_NBTHREADS` has a default value of (`1`), and is capped at ZSTDMT_NBWORKERS_MAX==200. `zstd` must be
compiled with multithread support for this to have any effect.
They can both be overridden by corresponding command line arguments:
`-#` for compression level and `-T#` for number of compression threads.
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