Disable the memory usage limiter by default.

For several people, the limiter causes bigger problems that
it solves, so it is better to have it disabled by default.
Those who want to have a limiter by default need to enable
it via the environment variable XZ_DEFAULTS.

Support for environment variable XZ_DEFAULTS was added. It is
parsed before XZ_OPT and technically identical with it. The
intended uses differ quite a bit though; see the man page.

The memory usage limit can now be set separately for
compression and decompression using --memlimit-compress and
--memlimit-decompress. To set both at once, -M or --memlimit
can be used. --memory was retained as a legacy alias for
--memlimit for backwards compatibility.

The semantics of --info-memory were changed in backwards
incompatible way. Compatibility wasn't meaningful due to
changes in the memory usage limiter functionality.

The memory usage limiter info is no longer shown at the
bottom of xz --long -help.

The memory usage limiter support for removed completely from xzdec.

xz's man page was updated to match the above changes. Various
unrelated fixes were also made to the man page.

1 files changed, 10 insertions, 29 deletions

diff --git a/src/xz/message.c b/src/xz/message.c
index 5044ea22..c62e2b2c 100644
--- a/src/xz/message.c
+++ b/src/xz/message.c
@@ -854,7 +854,7 @@ message_mem_needed(enum message_verbosity v, uint64_t memusage)
 	// Show the memory usage limit as MiB unless it is less than 1 MiB.
 	// This way it's easy to notice errors where one has typed
 	// --memory=123 instead of --memory=123MiB.
-	uint64_t memlimit = hardware_memlimit_get();
+	uint64_t memlimit = hardware_memlimit_get(opt_mode);
 	if (memlimit < (UINT32_C(1) << 20)) {
 		snprintf(memlimitstr, sizeof(memlimitstr), "%s B",
 				uint64_to_str(memlimit, 1));
@@ -1053,21 +1053,6 @@ message_try_help(void)
 
 
 extern void
-message_memlimit(void)
-{
-	if (opt_robot)
-		printf("%" PRIu64 "\n", hardware_memlimit_get());
-	else
-		printf(_("%s MiB (%s bytes)\n"),
-			uint64_to_str(
-				round_up_to_mib(hardware_memlimit_get()), 0),
-			uint64_to_str(hardware_memlimit_get(), 1));
-
-	tuklib_exit(E_SUCCESS, E_ERROR, verbosity != V_SILENT);
-}
-
-
-extern void
 message_version(void)
 {
 	// It is possible that liblzma version is different than the command
@@ -1138,12 +1123,16 @@ message_help(bool long_help)
 "                      ratio without increasing memory usage of the decoder"));
 
 	if (long_help) {
+		puts(_( // xgettext:no-c-format
+"      --memlimit-compress=LIMIT\n"
+"      --memlimit-decompress=LIMIT\n"
+"  -M, --memlimit=LIMIT\n"
+"                      set memory usage limit for compression, decompression,\n"
+"                      or both; LIMIT is in bytes, % of RAM, or 0 for defaults"));
+
 		puts(_(
 "      --no-adjust     if compression settings exceed the memory usage limit,\n"
 "                      give an error instead of adjusting the settings downwards"));
-		puts(_( // xgettext:no-c-format
-"  -M, --memory=NUM    use roughly NUM bytes of memory at maximum; 0 indicates\n"
-"                      the default setting, which is 40 % of total RAM"));
 	}
 
 	if (long_help) {
@@ -1201,7 +1190,8 @@ message_help(bool long_help)
 "      --robot         use machine-parsable messages (useful for scripts)"));
 		puts("");
 		puts(_(
-"      --info-memory   display the memory usage limit and exit"));
+"      --info-memory   display the total amount of RAM and the currently active\n"
+"                      memory usage limits, and exit"));
 		puts(_(
 "  -h, --help          display the short help (lists only the basic options)\n"
 "  -H, --long-help     display this long help and exit"));
@@ -1216,15 +1206,6 @@ message_help(bool long_help)
 
 	puts(_("\nWith no FILE, or when FILE is -, read standard input.\n"));
 
-	if (long_help) {
-		printf(_(
-"On this system and configuration, this program will use a maximum of roughly\n"
-"%s MiB RAM and "), uint64_to_str(round_up_to_mib(hardware_memlimit_get()), 0));
-		printf(N_("one thread.\n\n", "%s threads.\n\n",
-				hardware_threadlimit_get()),
-				uint64_to_str(hardware_threadlimit_get(), 0));
-	}
-
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