i18n: cache the result of every gettext call In looking at profiler output for 'hg log' on mozilla-central, I noticed we spent a _huge_ amount of time in gettext relative to what it's doing. Caching provides a roughly 15% performance improvement even on repositories as small as hg. == hg repo on linux == Before: % cumulative self time seconds seconds name 5.05 0.19 0.19 i18n.py:62:gettext 4.84 0.18 0.18 revlog.py:88:decompress 2.95 0.17 0.11 changelog.py:201:node 2.32 0.09 0.09 ui.py:577:write 2.11 0.08 0.08 i18n.py:72:gettext 2.11 0.08 0.08 obsolete.py:196:_fm0readmarkers 1.89 0.07 0.07 obsolete.py:569:_load 1.68 0.63 0.06 localrepo.py:29:__get__ real 0m4.026s user 0m3.993s sys 0m0.034s After: % cumulative self time seconds seconds name 8.05 0.26 0.26 revlog.py:88:decompress 2.68 0.22 0.09 color.py:395:write 2.20 0.07 0.07 obsolete.py:196:_fm0readmarkers 1.95 0.06 0.06 obsolete.py:174:_fm0readmarkers 1.95 0.06 0.06 ui.py:577:write 1.95 0.06 0.06 util.py:1228:datestr 1.71 0.06 0.06 utf_8.py:16:decode 1.71 0.06 0.06 revlog.py:273:__len__ real 0m3.519s user 0m3.447s sys 0m0.073s == mozilla-central repo on linux == Before: % cumulative self time seconds seconds name 7.72 2.35 2.35 revlog.py:88:decompress 4.46 1.36 1.36 i18n.py:62:gettext 2.22 0.67 0.67 i18n.py:72:gettext 2.19 1.14 0.67 changelog.py:201:node 2.16 0.66 0.66 ui.py:577:write 1.96 0.60 0.60 utf_8.py:16:decode 1.93 1.97 0.59 color.py:395:write 1.85 0.81 0.56 changelog.py:136:tip real 0m30.822s user 0m30.660s sys 0m0.149s After: % cumulative self time seconds seconds name 9.82 2.49 2.49 revlog.py:88:decompress 2.67 1.31 0.68 localrepo.py:29:__get__ 2.57 0.65 0.65 utf_8.py:16:decode 2.48 1.01 0.63 changelog.py:201:node 2.10 0.82 0.53 changelog.py:136:tip 2.01 0.51 0.51 ui.py:577:write 1.91 0.49 0.49 util.py:1232:datestr 1.85 1.65 0.47 color.py:395:write real 0m25.619s user 0m25.446s sys 0m0.166s == cpython repo on os x = Before: % cumulative self time seconds seconds name 5.05 1.35 1.35 cmdutil.py:982:_show 4.59 1.22 1.22 revlog.py:274:__len__ 3.98 1.06 1.06 i18n.py:62:gettext 3.91 1.04 1.04 revlog.py:1016:revision 3.68 0.98 0.98 revlog.py:337:parents 3.45 0.92 0.92 revlog.py:88:decompress 2.91 0.78 0.78 revlog.py:309:rev 2.62 0.70 0.70 revlog.py:1033:revision real 0m30.414s user 0m28.145s sys 0m0.541s After: % cumulative self time seconds seconds name 7.98 1.66 1.66 cmdutil.py:982:_show 6.83 1.42 1.42 changelog.py:46:decodeextra 5.18 1.08 1.08 revlog.py:274:__len__ 3.94 0.82 0.82 revlog.py:1016:revision 3.41 0.71 0.71 revlog.py:309:rev 3.32 0.69 0.69 revlog.py:88:decompress 2.99 0.63 0.62 revlog.py:1033:revision 2.69 0.56 0.56 revlog.py:341:start real 0m22.811s user 0m21.883s sys 0m0.397s