diff options
Diffstat (limited to 'programs/zstd.1')
| -rw-r--r-- | programs/zstd.1 | 34 |
1 files changed, 19 insertions, 15 deletions
diff --git a/programs/zstd.1 b/programs/zstd.1 index 674f89841ce8a..c93755f877edd 100644 --- a/programs/zstd.1 +++ b/programs/zstd.1 @@ -1,5 +1,5 @@ . -.TH "ZSTD" "1" "October 2018" "zstd 1.3.7" "User Commands" +.TH "ZSTD" "1" "December 2018" "zstd 1.3.8" "User Commands" . .SH "NAME" \fBzstd\fR \- zstd, zstdmt, unzstd, zstdcat \- Compress or decompress \.zst files @@ -127,6 +127,10 @@ Does not spawn a thread for compression, use a single thread for both I/O and co \fBzstd\fR will dynamically adapt compression level to perceived I/O conditions\. Compression level adaptation can be observed live by using command \fB\-v\fR\. Adaptation can be constrained between supplied \fBmin\fR and \fBmax\fR levels\. The feature works when combined with multi\-threading and \fB\-\-long\fR mode\. It does not work with \fB\-\-single\-thread\fR\. It sets window size to 8 MB by default (can be changed manually, see \fBwlog\fR)\. Due to the chaotic nature of dynamic adaptation, compressed result is not reproducible\. \fInote\fR : at the time of this writing, \fB\-\-adapt\fR can remain stuck at low speed when combined with multiple worker threads (>=2)\. . .TP +\fB\-\-rsyncable\fR +\fBzstd\fR will periodically synchronize the compression state to make the compressed file more rsync\-friendly\. There is a negligible impact to compression ratio, and the faster compression levels will see a small compression speed hit\. This feature does not work with \fB\-\-single\-thread\fR\. You probably don\'t want to use it with long range mode, since it will decrease the effectiveness of the synchronization points, but your milage may vary\. +. +.TP \fB\-D file\fR use \fBfile\fR as Dictionary to compress or decompress FILE(s) . @@ -312,7 +316,7 @@ set process priority to real\-time Specify a strategy used by a match finder\. . .IP -There are 8 strategies numbered from 1 to 8, from faster to stronger: 1=ZSTD_fast, 2=ZSTD_dfast, 3=ZSTD_greedy, 4=ZSTD_lazy, 5=ZSTD_lazy2, 6=ZSTD_btlazy2, 7=ZSTD_btopt, 8=ZSTD_btultra\. +There are 9 strategies numbered from 1 to 9, from faster to stronger: 1=ZSTD_fast, 2=ZSTD_dfast, 3=ZSTD_greedy, 4=ZSTD_lazy, 5=ZSTD_lazy2, 6=ZSTD_btlazy2, 7=ZSTD_btopt, 8=ZSTD_btultra, 9=ZSTD_btultra2\. . .TP \fBwindowLog\fR=\fIwlog\fR, \fBwlog\fR=\fIwlog\fR @@ -355,21 +359,21 @@ More searches increases the chance to find a match which usually increases compr The minimum \fIslog\fR is 1 and the maximum is 26\. . .TP -\fBsearchLength\fR=\fIslen\fR, \fBslen\fR=\fIslen\fR +\fBminMatch\fR=\fImml\fR, \fBmml\fR=\fImml\fR Specify the minimum searched length of a match in a hash table\. . .IP Larger search lengths usually decrease compression ratio but improve decompression speed\. . .IP -The minimum \fIslen\fR is 3 and the maximum is 7\. +The minimum \fImml\fR is 3 and the maximum is 7\. . .TP \fBtargetLen\fR=\fItlen\fR, \fBtlen\fR=\fItlen\fR The impact of this field vary depending on selected strategy\. . .IP -For ZSTD_btopt and ZSTD_btultra, it specifies the minimum match length that causes match finder to stop searching for better matches\. A larger \fBtargetLen\fR usually improves compression ratio but decreases compression speed\. +For ZSTD_btopt, ZSTD_btultra and ZSTD_btultra2, it specifies the minimum match length that causes match finder to stop searching\. A larger \fBtargetLen\fR usually improves compression ratio but decreases compression speed\. . .IP For ZSTD_fast, it triggers ultra\-fast mode when > 0\. The value represents the amount of data skipped between match sampling\. Impact is reversed : a larger \fBtargetLen\fR increases compression speed but decreases compression ratio\. @@ -385,10 +389,10 @@ The minimum \fItlen\fR is 0 and the maximum is 999\. Determine \fBoverlapSize\fR, amount of data reloaded from previous job\. This parameter is only available when multithreading is enabled\. Reloading more data improves compression ratio, but decreases speed\. . .IP -The minimum \fIovlog\fR is 0, and the maximum is 9\. 0 means "no overlap", hence completely independent jobs\. 9 means "full overlap", meaning up to \fBwindowSize\fR is reloaded from previous job\. Reducing \fIovlog\fR by 1 reduces the amount of reload by a factor 2\. Default \fIovlog\fR is 6, which means "reload \fBwindowSize / 8\fR"\. Exception : the maximum compression level (22) has a default \fIovlog\fR of 9\. +The minimum \fIovlog\fR is 0, and the maximum is 9\. 1 means "no overlap", hence completely independent jobs\. 9 means "full overlap", meaning up to \fBwindowSize\fR is reloaded from previous job\. Reducing \fIovlog\fR by 1 reduces the reloaded amount by a factor 2\. For example, 8 means "windowSize/2", and 6 means "windowSize/8"\. Value 0 is special and means "default" : \fIovlog\fR is automatically determined by \fBzstd\fR\. In which case, \fIovlog\fR will range from 6 to 9, depending on selected \fIstrat\fR\. . .TP -\fBldmHashLog\fR=\fIldmhlog\fR, \fBldmhlog\fR=\fIldmhlog\fR +\fBldmHashLog\fR=\fIlhlog\fR, \fBlhlog\fR=\fIlhlog\fR Specify the maximum size for a hash table used for long distance matching\. . .IP @@ -398,10 +402,10 @@ This option is ignored unless long distance matching is enabled\. Bigger hash tables usually improve compression ratio at the expense of more memory during compression and a decrease in compression speed\. . .IP -The minimum \fIldmhlog\fR is 6 and the maximum is 26 (default: 20)\. +The minimum \fIlhlog\fR is 6 and the maximum is 26 (default: 20)\. . .TP -\fBldmSearchLength\fR=\fIldmslen\fR, \fBldmslen\fR=\fIldmslen\fR +\fBldmMinMatch\fR=\fIlmml\fR, \fBlmml\fR=\fIlmml\fR Specify the minimum searched length of a match for long distance matching\. . .IP @@ -411,10 +415,10 @@ This option is ignored unless long distance matching is enabled\. Larger/very small values usually decrease compression ratio\. . .IP -The minimum \fIldmslen\fR is 4 and the maximum is 4096 (default: 64)\. +The minimum \fIlmml\fR is 4 and the maximum is 4096 (default: 64)\. . .TP -\fBldmBucketSizeLog\fR=\fIldmblog\fR, \fBldmblog\fR=\fIldmblog\fR +\fBldmBucketSizeLog\fR=\fIlblog\fR, \fBlblog\fR=\fIlblog\fR Specify the size of each bucket for the hash table used for long distance matching\. . .IP @@ -424,10 +428,10 @@ This option is ignored unless long distance matching is enabled\. Larger bucket sizes improve collision resolution but decrease compression speed\. . .IP -The minimum \fIldmblog\fR is 0 and the maximum is 8 (default: 3)\. +The minimum \fIlblog\fR is 0 and the maximum is 8 (default: 3)\. . .TP -\fBldmHashEveryLog\fR=\fIldmhevery\fR, \fBldmhevery\fR=\fIldmhevery\fR +\fBldmHashRateLog\fR=\fIlhrlog\fR, \fBlhrlog\fR=\fIlhrlog\fR Specify the frequency of inserting entries into the long distance matching hash table\. . .IP @@ -437,13 +441,13 @@ This option is ignored unless long distance matching is enabled\. Larger values will improve compression speed\. Deviating far from the default value will likely result in a decrease in compression ratio\. . .IP -The default value is \fBwlog \- ldmhlog\fR\. +The default value is \fBwlog \- lhlog\fR\. . .SS "Example" The following parameters sets advanced compression options to something similar to predefined level 19 for files bigger than 256 KB: . .P -\fB\-\-zstd\fR=wlog=23,clog=23,hlog=22,slog=6,slen=3,tlen=48,strat=6 +\fB\-\-zstd\fR=wlog=23,clog=23,hlog=22,slog=6,mml=3,tlen=48,strat=6 . .SS "\-B#:" Select the size of each compression job\. This parameter is available only when multi\-threading is enabled\. Default value is \fB4 * windowSize\fR, which means it varies depending on compression level\. \fB\-B#\fR makes it possible to select a custom value\. Note that job size must respect a minimum value which is enforced transparently\. This minimum is either 1 MB, or \fBoverlapSize\fR, whichever is largest\. |