On 15.05.2017 12:04, Markus Trippelsdorf wrote: > On 2017.05.15 at 16:24 +0200, Jakub Jelinek wrote: >> On Mon, May 15, 2017 at 04:13:44PM +0200, Markus Trippelsdorf wrote: >>> On 2017.05.15 at 14:02 +0000, Joseph Myers wrote: >>>> The xz manpage warns against blindly using -9 (for which --best is a >>>> deprecated alias) because of the implications for memory requirements for >>>> decompressing. If there's a reason it's considered appropriate here, I >>>> think it needs an explanatory comment. >>> >>> I think it is unacceptable, because it would increase memory usage when >>> decompressing over 20x compared to bz2 (and over 100x while compressing). >> >> The memory using during compressing isn't that interesting as long as it >> isn't prohibitive for sourceware or the machines RMs use. >> For the decompression, I guess it matters what is actually the memory needed >> for decompression the -9 gcc tarball, and compare that to minimal memory >> requirements to compile (not bootstrap) the compiler using typical system >> compilers. If compilation of gcc takes more memory than the decompression, >> then it should be fine, why would anyone try to decompress gcc not to build >> it afterwards? > > Ok, it doesn't really matter. With gcc-7.1 tarball: > > size: 533084160 (uncompressed) > > -9: > xz -d gcc.tar.xz > 4.71user 0.26system 0:04.97elapsed 100%CPU (0avgtext+0avgdata > 67804maxresident)k > size: 60806928 > > -6 (default): > xz -d gcc.tar.xz > 4.88user 0.28system 0:05.17elapsed 99%CPU (0avgtext+0avgdata > 10324maxresident)k > size: 65059664 > > So -9 is actually just fine.
ok, updated the script to use xz --best by default. trunk and the gcc-7-branch. Matthias
