sort: FEATURE_SORT_OPTIMIZE_MEMORY
On sorting all kernel/linux/arch/ *.[ch] files, this reduces memory usage by 6%. yes | head -99999999 | sort goes down from 1900Mb to 380 Mb. function old new delta sort_main 862 1098 +236 Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
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Denys Vlasenko
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@ -18,16 +18,24 @@
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//config: sort is used to sort lines of text in specified files.
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//config:
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//config:config FEATURE_SORT_BIG
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//config: bool "Full SuSv3 compliant sort (support -ktcsbdfiozgM)"
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//config: bool "Full SuSv3 compliant sort (support -ktcbdfiozgM)"
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//config: default y
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//config: depends on SORT
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//config: help
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//config: Without this, sort only supports -r, -u, and an integer version
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//config: Without this, sort only supports -r, -u, -s, and an integer version
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//config: of -n. Selecting this adds sort keys, floating point support, and
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//config: more. This adds a little over 3k to a nonstatic build on x86.
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//config:
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//config: The SuSv3 sort standard is available at:
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//config: http://www.opengroup.org/onlinepubs/007904975/utilities/sort.html
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//config:
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//config:config FEATURE_SORT_OPTIMIZE_MEMORY
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//config: bool "Use less memory (but might be slower)"
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//config: default n # defaults to N since we are size-paranoid tribe
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//config: depends on SORT
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//config: help
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//config: Attempt to use less memory (by storing only one copy
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//config: of duplicated lines, and such). Useful if you work on huge files.
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//applet:IF_SORT(APPLET_NOEXEC(sort, sort, BB_DIR_USR_BIN, BB_SUID_DROP, sort))
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@ -46,19 +54,17 @@
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//usage: "\n -f Ignore case"
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//usage: "\n -i Ignore unprintable characters"
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//usage: "\n -d Dictionary order (blank or alphanumeric only)"
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//usage: "\n -g General numerical sort"
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//usage: "\n -M Sort month"
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//usage: )
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//-h, --human-numeric-sort: compare human readable numbers (e.g., 2K 1G)
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//usage: "\n -n Sort numbers"
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//usage: IF_FEATURE_SORT_BIG(
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//usage: "\n -g General numerical sort"
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//usage: "\n -M Sort month"
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//usage: "\n -t CHAR Field separator"
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//usage: "\n -k N[,M] Sort by Nth field"
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//usage: )
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//usage: "\n -r Reverse sort order"
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//usage: IF_FEATURE_SORT_BIG(
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//usage: "\n -s Stable (don't sort ties alphabetically)"
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//usage: )
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//usage: "\n -u Suppress duplicate lines"
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//usage: IF_FEATURE_SORT_BIG(
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//usage: "\n -z Lines are terminated by NUL, not newline"
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@ -404,6 +410,14 @@ int sort_main(int argc UNUSED_PARAM, char **argv)
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int i;
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int linecount;
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unsigned opts;
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#if ENABLE_FEATURE_SORT_OPTIMIZE_MEMORY
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bool can_drop_dups;
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size_t prev_len = 0;
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/* Postpone optimizing if the input is small, < 16k lines:
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* even just free()ing duplicate lines takes time.
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*/
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size_t count_to_optimize_dups = 0x3fff;
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#endif
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xfunc_error_retval = 2;
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@ -412,6 +426,29 @@ int sort_main(int argc UNUSED_PARAM, char **argv)
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sort_opt_str,
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&str_ignored, &str_ignored, &str_o, &lst_k, &str_t
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);
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#if ENABLE_FEATURE_SORT_OPTIMIZE_MEMORY
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/* Can drop dups only if -u but no "complicating" options,
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* IOW: if we do a full line compares. Safe options:
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* -o FILE Output to FILE
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* -z Lines are terminated by NUL, not newline
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* -r Reverse sort order
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* -s Stable (don't sort ties alphabetically)
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* Not sure about these:
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* -b Ignore leading blanks
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* -f Ignore case
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* -i Ignore unprintable characters
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* -d Dictionary order (blank or alphanumeric only)
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* -n Sort numbers
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* -g General numerical sort
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* -M Sort month
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*/
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can_drop_dups = ((opts & ~(FLAG_o|FLAG_z|FLAG_r|FLAG_s)) == FLAG_u);
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/* Stable sort needs every line to be uniquely allocated,
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* disable optimization to reuse strings:
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*/
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if (opts & FLAG_s)
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count_to_optimize_dups = (size_t)-1L;
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#endif
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/* global b strips leading and trailing spaces */
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if (opts & FLAG_b)
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option_mask32 |= FLAG_bb;
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@ -489,6 +526,41 @@ int sort_main(int argc UNUSED_PARAM, char **argv)
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char *line = GET_LINE(fp);
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if (!line)
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break;
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#if ENABLE_FEATURE_SORT_OPTIMIZE_MEMORY
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if (count_to_optimize_dups != 0)
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count_to_optimize_dups--;
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if (count_to_optimize_dups == 0) {
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size_t len;
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char *new_line;
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char first = *line;
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/* On kernel/linux/arch/ *.[ch] files,
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* this reduces memory usage by 6%.
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* yes | head -99999999 | sort
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* goes down from 1900Mb to 380 Mb.
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*/
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if (first == '\0' || first == '\n') {
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len = !(first == '\0');
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new_line = (char*)"\n" + 1 - len;
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goto replace;
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}
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len = strlen(line);
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if (len <= prev_len) {
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new_line = lines[linecount-1] + (prev_len - len);
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if (strcmp(line, new_line) == 0) {
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if (can_drop_dups && prev_len == len) {
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free(line);
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continue;
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}
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replace:
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free(line);
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line = new_line;
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}
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}
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prev_len = len;
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}
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#endif
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lines = xrealloc_vector(lines, 6, linecount);
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lines[linecount++] = line;
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}
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@ -510,6 +582,8 @@ int sort_main(int argc UNUSED_PARAM, char **argv)
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}
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return EXIT_SUCCESS;
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}
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#else
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//TODO: lighter version which only drops total dups if can_drop_dups == true
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#endif
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/* For stable sort, store original line position beyond terminating NUL */
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