upstream/mercurial-mirror Files · contrib/chg/util.h

util: implement zstd compression engine...

util: implement zstd compression engine Now that zstd is vendored and being built (in some configurations), we can implement a compression engine for zstd! The zstd engine is a little different from existing engines. Because it may not always be present, we have to defer load the module in case importing it fails. We facilitate this via a cached property that holds a reference to the module or None. The "available" method is implemented to reflect reality. The zstd engine declares its ability to handle bundles using the "zstd" human name and the "ZS" internal name. The latter was chosen because internal names are 2 characters (by only convention I think) and "ZS" seems reasonable. The engine, like others, supports specifying the compression level. However, there are no consumers of this API that yet pass in that argument. I have plans to change that, so stay tuned. Since all we need to do to support bundle generation with a new compression engine is implement and register the compression engine, bundle generation with zstd "just works!" Tests demonstrating this have been added. How does performance of zstd for bundle generation compare? On the mozilla-unified repo, `hg bundle --all -t <engine>-v2` yields the following on my i7-6700K on Linux: engine CPU time bundle size vs orig size throughput none 97.0s 4,054,405,584 100.0% 41.8 MB/s bzip2 (l=9) 393.6s 975,343,098 24.0% 10.3 MB/s gzip (l=6) 184.0s 1,140,533,074 28.1% 22.0 MB/s zstd (l=1) 108.2s 1,119,434,718 27.6% 37.5 MB/s zstd (l=2) 111.3s 1,078,328,002 26.6% 36.4 MB/s zstd (l=3) 113.7s 1,011,823,727 25.0% 35.7 MB/s zstd (l=4) 116.0s 1,008,965,888 24.9% 35.0 MB/s zstd (l=5) 121.0s 977,203,148 24.1% 33.5 MB/s zstd (l=6) 131.7s 927,360,198 22.9% 30.8 MB/s zstd (l=7) 139.0s 912,808,505 22.5% 29.2 MB/s zstd (l=12) 198.1s 854,527,714 21.1% 20.5 MB/s zstd (l=18) 681.6s 789,750,690 19.5% 5.9 MB/s On compression, zstd for bundle generation delivers: * better compression than gzip with significantly less CPU utilization * better than bzip2 compression ratios while still being significantly faster than gzip * ability to aggressively tune compression level to achieve significantly smaller bundles That last point is important. With clone bundles, a server can pre-generate a bundle file, upload it to a static file server, and redirect clients to transparently download it during clone. The server could choose to produce a zstd bundle with the highest compression settings possible. This would take a very long time - a magnitude longer than a typical zstd bundle generation - but the result would be hundreds of megabytes smaller! For the clone volume we do at Mozilla, this could translate to petabytes of bandwidth savings per year and faster clones (due to smaller transfer size). I don't have detailed numbers to report on decompression. However, zstd decompression is fast: >1 GB/s output throughput on this machine, even through the Python bindings. And it can do that regardless of the compression level of the input. By the time you have enough data to worry about overhead of decompression, you have plenty of other things to worry about performance wise. zstd is wins all around. I can't wait to implement support for it on the wire protocol and in revlogs.

Yuya Nishihara - - Load All Authors

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        Yuya Nishihara
    
chg: import frontend sources...

              r28060
            
      /*

       * Utility functions

       *

       * Copyright (c) 2011 Yuya Nishihara <yuya@tcha.org>

       *

       * This software may be used and distributed according to the terms of the

       * GNU General Public License version 2 or any later version.

       */

      #ifndef UTIL_H_

      #define UTIL_H_

      #ifdef __GNUC__

      #define PRINTF_FORMAT_ __attribute__((format(printf, 1, 2)))

        Yuya Nishihara
    
chg: silence warning of unused parameter 'sig'

              r29440
            
      #define UNUSED_ __attribute__((unused))

        Jun Wu
    
chg: define PRINTF_FORMAT_ for non gnu C compiler...

              r28604
            
      #else

      #define PRINTF_FORMAT_

        Yuya Nishihara
    
chg: silence warning of unused parameter 'sig'

              r29440
            
      #define UNUSED_

        Yuya Nishihara
    
chg: import frontend sources...

              r28060
            
      #endif

      void abortmsg(const char *fmt, ...) PRINTF_FORMAT_;

        Jun Wu
    
chg: add util function abortmsgerrno to print error with errno...

              r28788
            
      void abortmsgerrno(const char *fmt, ...) PRINTF_FORMAT_;

        Yuya Nishihara
    
chg: import frontend sources...

              r28060
            
        Jun Wu
    
chg: use color in debug/error messages conditionally...

              r28787
            
      void enablecolor(void);

        Yuya Nishihara
    
chg: import frontend sources...

              r28060
            
      void enabledebugmsg(void);

      void debugmsg(const char *fmt, ...) PRINTF_FORMAT_;

        Jun Wu
    
chg: add fchdirx as a utility function...

              r28854
            
      void fchdirx(int dirfd);

        Jun Wu
    
chg: extract the logic of setting FD_CLOEXEC to a utility function...

              r28855
            
      void fsetcloexec(int fd);

        Jun Wu
    
chg: add utility functions mallocx, reallocx...

              r28165
            
      void *mallocx(size_t size);

      void *reallocx(void *ptr, size_t size);

        Yuya Nishihara
    
chg: import frontend sources...

              r28060
            
      int runshellcmd(const char *cmd, const char *envp[], const char *cwd);

      #endif  /* UTIL_H_ */

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Yuya Nishihara chg: import frontend sources...	r28060	/*
		* Utility functions
		*
		* Copyright (c) 2011 Yuya Nishihara <yuya@tcha.org>
		*
		* This software may be used and distributed according to the terms of the
		* GNU General Public License version 2 or any later version.
		*/

		#ifndef UTIL_H_
		#define UTIL_H_

		#ifdef __GNUC__
		#define PRINTF_FORMAT_ __attribute__((format(printf, 1, 2)))
Yuya Nishihara chg: silence warning of unused parameter 'sig'	r29440	#define UNUSED_ __attribute__((unused))
Jun Wu chg: define PRINTF_FORMAT_ for non gnu C compiler...	r28604	#else
		#define PRINTF_FORMAT_
Yuya Nishihara chg: silence warning of unused parameter 'sig'	r29440	#define UNUSED_
Yuya Nishihara chg: import frontend sources...	r28060	#endif

		void abortmsg(const char *fmt, ...) PRINTF_FORMAT_;
Jun Wu chg: add util function abortmsgerrno to print error with errno...	r28788	void abortmsgerrno(const char *fmt, ...) PRINTF_FORMAT_;
Yuya Nishihara chg: import frontend sources...	r28060
Jun Wu chg: use color in debug/error messages conditionally...	r28787	void enablecolor(void);
Yuya Nishihara chg: import frontend sources...	r28060	void enabledebugmsg(void);
		void debugmsg(const char *fmt, ...) PRINTF_FORMAT_;

Jun Wu chg: add fchdirx as a utility function...	r28854	void fchdirx(int dirfd);
Jun Wu chg: extract the logic of setting FD_CLOEXEC to a utility function...	r28855	void fsetcloexec(int fd);
Jun Wu chg: add utility functions mallocx, reallocx...	r28165	void *mallocx(size_t size);
		void reallocx(void ptr, size_t size);

Yuya Nishihara chg: import frontend sources...	r28060	int runshellcmd(const char cmd, const char envp[], const char *cwd);

		#endif /* UTIL_H_ */