From 8a38e972384e7d049e6d63d7ae4d8893df870fc3 Mon Sep 17 00:00:00 2001 From: Lee Daly Date: Thu, 24 May 2018 12:04:49 +0100 Subject: [PATCH] doc: add compression level guide for ISA-L This expands the ISA-L documentation to give more a detailed explanation of the mapping between the compressdev API levels and PMD levels. Signed-off-by: Lee Daly Acked-by: Marko Kovacevic --- doc/guides/compressdevs/isal.rst | 65 ++++++++++++++++++++++++++++---- 1 file changed, 57 insertions(+), 8 deletions(-) diff --git a/doc/guides/compressdevs/isal.rst b/doc/guides/compressdevs/isal.rst index 2024437c7e..276ff06305 100644 --- a/doc/guides/compressdevs/isal.rst +++ b/doc/guides/compressdevs/isal.rst @@ -6,7 +6,8 @@ ISA-L Compression Poll Mode Driver The ISA-L PMD (**librte_pmd_isal_comp**) provides poll mode compression & decompression driver support for utilizing Intel ISA-L library, -which implements the deflate algorithm for both compression and decompression +which implements the deflate algorithm for both Deflate(compression) and Inflate(decompression). + Features -------- @@ -15,25 +16,73 @@ ISA-L PMD has support for: Compression/Decompression algorithm: -* DEFLATE + * DEFLATE Huffman code type: -* FIXED -* DYNAMIC + * FIXED + * DYNAMIC Window size support: -* 32K + * 32K + +Level guide: + +The ISA-L levels have been mapped to somewhat correspond to the same ZLIB level, +i.e. ZLIB L1 gives a compression ratio similar to ISA-L L1. +Compressdev level 0 enables "No Compression", which passes the uncompressed +data to the output buffer, plus deflate headers. +The ISA-L library does not support this, therefore compressdev level 0 is not supported. + +The compressdev API has 10 levels, 0-9. ISA-L has 4 levels of compression, 0-3. +As a result the level mappings from the API to the PMD are shown below. + +.. _table_ISA-L_compression_levels: + +.. table:: Level mapping from Compressdev to ISA-L PMD. + + +-------------+----------------------------------------------+-----------------------------------------------+ + | Compressdev | PMD Functionality | Internal ISA-L | + | API Level | | Level | + +=============+==============================================+===============================================+ + | 0 | No compression, Not Supported | --- | + +-------------+----------------------------------------------+-----------------------------------------------+ + | 1 | Dynamic (Fast compression) | 1 | + +-------------+----------------------------------------------+-----------------------------------------------+ + | 2 | Dynamic | 2 | + | | (Higher compression ratio) | | + +-------------+----------------------------------------------+-----------------------------------------------+ + | 3 | Dynamic | 3 | + | | (Best compression ratio) | (Level 2 if | + | | | no AVX512/AVX2) | + +-------------+----------------------------------------------+-----------------------------------------------+ + | 4 | Dynamic (Best compression ratio) | Same as above | + +-------------+----------------------------------------------+-----------------------------------------------+ + | 5 | Dynamic (Best compression ratio) | Same as above | + +-------------+----------------------------------------------+-----------------------------------------------+ + | 6 | Dynamic (Best compression ratio) | Same as above | + +-------------+----------------------------------------------+-----------------------------------------------+ + | 7 | Dynamic (Best compression ratio) | Same as above | + +-------------+----------------------------------------------+-----------------------------------------------+ + | 8 | Dynamic (Best compression ratio) | Same as above | + +-------------+----------------------------------------------+-----------------------------------------------+ + | 9 | Dynamic (Best compression ratio) | Same as above | + +-------------+----------------------------------------------+-----------------------------------------------+ + +.. Note:: + + The above table only shows mapping when API calls for dynamic compression. + For fixed compression, regardless of API level, internally ISA-L level 0 is always used. Limitations ----------- -* Chained mbufs are not supported, for future release. +* Chained mbufs will not be supported until a future release, meaning max data size being passed to PMD through a single mbuf is 64K - 1. If data is larger than this it will need to be split up and sent as multiple operations. -* Compressdev level 0, no compression, is not supported. ISA-L level 0 used for fixed huffman codes. +* Compressdev level 0, no compression, is not supported. -* Checksums are not supported, for future release. +* Checksums will not be supported until future release. Installation ------------ -- 2.20.1