diff options
Diffstat (limited to 'src/xz')
| -rw-r--r-- | src/xz/hardware.c | 32 | ||||
| -rw-r--r-- | src/xz/xz.1 | 19 |
2 files changed, 50 insertions, 1 deletions
diff --git a/src/xz/hardware.c b/src/xz/hardware.c index ff32f6d30148..e746cf91a76f 100644 --- a/src/xz/hardware.c +++ b/src/xz/hardware.c @@ -68,9 +68,39 @@ hardware_memlimit_set(uint64_t new_memlimit, new_memlimit = (uint32_t)new_memlimit * total_ram / 100; } - if (set_compress) + if (set_compress) { memlimit_compress = new_memlimit; +#if SIZE_MAX == UINT32_MAX + // FIXME? + // + // When running a 32-bit xz on a system with a lot of RAM and + // using a percentage-based memory limit, the result can be + // bigger than the 32-bit address space. Limiting the limit + // below SIZE_MAX for compression (not decompression) makes + // xz lower the compression settings (or number of threads) + // to a level that *might* work. In practice it has worked + // when using a 64-bit kernel that gives full 4 GiB address + // space to 32-bit programs. In other situations this might + // still be too high, like 32-bit kernels that may give much + // less than 4 GiB to a single application. + // + // So this is an ugly hack but I will keep it here while + // it does more good than bad. + // + // Use a value less than SIZE_MAX so that there's some room + // for the xz program and so on. Don't use 4000 MiB because + // it could look like someone mixed up base-2 and base-10. + const uint64_t limit_max = UINT64_C(4020) << 20; + + // UINT64_MAX is a special case for the string "max" so + // that has to be handled specially. + if (memlimit_compress != UINT64_MAX + && memlimit_compress > limit_max) + memlimit_compress = limit_max; +#endif + } + if (set_decompress) memlimit_decompress = new_memlimit; diff --git a/src/xz/xz.1 b/src/xz/xz.1 index 9dffdc6f82be..a4aaa0027ecb 100644 --- a/src/xz/xz.1 +++ b/src/xz/xz.1 @@ -1005,6 +1005,25 @@ instead of until the details have been decided. .RE .IP "" +For 32-bit +.BR xz +there is a special case: if the +.I limit +would be over +.BR "4020\ MiB" , +the +.I limit +is set to +.BR "4020\ MiB" . +(The values +.B 0 +and +.B max +aren't affected by this. +A similar feature doesn't exist for decompression.) +This can be helpful when a 32-bit executable has access +to 4\ GiB address space while hopefully doing no harm in other situations. +.IP "" See also the section .BR "Memory usage" . .TP |