forked from pool/systemd
83 lines
3.1 KiB
Diff
83 lines
3.1 KiB
Diff
Based on 1930eed2a7855d2df06ccf51f9e394428bf547e2 Mon Sep 17 00:00:00 2001
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From: Jon Severinsson <jon@severinsson.net>
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Date: Tue, 8 Jul 2014 18:29:46 +0200
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Subject: [PATCH] journal/compress: improve xz compression performance
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The new lzma2 compression options at the top of compress_blob_xz are
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equivalent to using preset "0", exept for using a 1 MiB dictionary
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(the same as preset "1"). This makes the memory usage at most 7.5 MiB
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in the compressor, and 1 MiB in the decompressor, instead of the
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previous 92 MiB in the compressor and 8 MiB in the decompressor.
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According to test-compress-benchmark this commit makes XZ compression
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20 times faster, with no increase in compressed data size.
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Using more realistic test data (an ELF binary rather than repeating
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ASCII letters 'a' through 'z' in order) it only provides a factor 10
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speedup, and at a cost if a 10% increase in compressed data size.
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But that is still a worthwhile trade-off.
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According to test-compress-benchmark XZ compression is still 25 times
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slower than LZ4, but the compressed data is one eighth the size.
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Using more realistic test data XZ compression is only 18 times slower
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than LZ4, and the compressed data is only one quarter the size.
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---
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src/journal/compress.c | 33 ++++++++++++++-------------------
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1 file changed, 14 insertions(+), 19 deletions(-)
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--- src/journal/compress.c
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+++ src/journal/compress.c 2014-07-09 12:09:45.814235274 +0000
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@@ -28,8 +28,15 @@
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#include "compress.h"
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bool compress_blob(const void *src, uint64_t src_size, void *dst, uint64_t *dst_size) {
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- lzma_stream s = LZMA_STREAM_INIT;
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+ static const lzma_options_lzma opt = {
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+ 1u << 20u, NULL, 0, LZMA_LC_DEFAULT, LZMA_LP_DEFAULT,
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+ LZMA_PB_DEFAULT, LZMA_MODE_FAST, 128, LZMA_MF_HC3, 4};
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+ static const lzma_filter filters[2] = {
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+ {LZMA_FILTER_LZMA2, (lzma_options_lzma*) &opt},
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+ {LZMA_VLI_UNKNOWN, NULL}
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+ };
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lzma_ret ret;
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+ size_t out_pos = 0;
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bool b = false;
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assert(src);
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@@ -40,29 +47,17 @@ bool compress_blob(const void *src, uint
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/* Returns false if we couldn't compress the data or the
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* compressed result is longer than the original */
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- ret = lzma_easy_encoder(&s, LZMA_PRESET_DEFAULT, LZMA_CHECK_NONE);
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- if (ret != LZMA_OK)
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+ if (src_size < 80)
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return false;
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- s.next_in = src;
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- s.avail_in = src_size;
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- s.next_out = dst;
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- s.avail_out = src_size;
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-
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- /* Does it fit? */
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- if (lzma_code(&s, LZMA_FINISH) != LZMA_STREAM_END)
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- goto fail;
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-
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- /* Is it actually shorter? */
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- if (s.avail_out == 0)
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- goto fail;
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+ ret = lzma_stream_buffer_encode((lzma_filter*) filters, LZMA_CHECK_NONE, NULL,
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+ src, src_size, dst, &out_pos, src_size - 1);
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+ if (ret != LZMA_OK)
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+ return false;
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- *dst_size = src_size - s.avail_out;
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+ *dst_size = out_pos;
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b = true;
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-fail:
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- lzma_end(&s);
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-
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return b;
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}
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