Nguyễn Thái Ngọc Duy <pclouds@xxxxxxxxx> writes: > Index format v4 requires some more computation to assemble a path > based on a previous one. The current code is not very efficient > because > > - it doubles memory copy, we assemble the final path in a temporary > first before putting it back to a cache_entry > > - strbuf_remove() in expand_name_field() is not exactly a good fit > for stripping a part at the end, _setlen() would do the same job > and is much cheaper. > > - the open-coded loop to find the end of the string in > expand_name_field() can't beat an optimized strlen() > > This patch avoids the temporary buffer and writes directly to the new > cache_entry, which addresses the first two points. The last point > could also be avoided if the total string length fits in the first 12 > bits of ce_flags, if not we fall back to strlen(). > > Running "test-tool read-cache 100" on webkit.git (275k files), reading > v2 only takes 4.226 seconds, while v4 takes 5.711 seconds, 35% more > time. The patch reduces read time on v4 to 4.319 seconds. > > Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@xxxxxxxxx> > --- > read-cache.c | 128 ++++++++++++++++++++++++--------------------------- > 1 file changed, 60 insertions(+), 68 deletions(-) Thanks; this round is much easier to read with a clearly named "expand_name_field" boolean variable, etc.
