Thomas Rast 6942efcfa9 xdiff: load full words in the inner loop of xdl_hash_record ... Redo the hashing loop in xdl_hash_record in a way that loads an entire 'long' at a time, using masking tricks to see when and where we found the terminating '\n'. I stole inspiration and code from the posts by Linus Torvalds around https://lkml.org/lkml/2012/3/2/452 https://lkml.org/lkml/2012/3/5/6 His method reads the buffers in sizeof(long) increments, and may thus overrun it by at most sizeof(long)-1 bytes before it sees the final newline (or hits the buffer length check). I considered padding out all buffers by a suitable amount to "catch" the overrun, but * this does not work for mmap()'d buffers: if you map 4096+8 bytes from a 4096 byte file, accessing the last 8 bytes results in a SIGBUS on my machine; and * it would also be extremely ugly because it intrudes deep into the unpacking machinery. So I adapted it to not read beyond the buffer at all. Instead, it reads the final partial word byte-by-byte and strings it together. Then it can use the same logic as before to finish the hashing. So far we enable this only on x86_64, where it provides nice speedup for diff-related work: Test origin/next tr/xdiff-fast-hash ----------------------------------------------------------------------------- 4000.1: log -3000 (baseline) 0.07(0.05+0.02) 0.08(0.06+0.02) +14.3% 4000.2: log --raw -3000 (tree-only) 0.37(0.33+0.04) 0.37(0.32+0.04) +0.0% 4000.3: log -p -3000 (Myers) 1.75(1.65+0.09) 1.60(1.49+0.10) -8.6% 4000.4: log -p -3000 --histogram 1.73(1.62+0.09) 1.58(1.49+0.08) -8.7% 4000.5: log -p -3000 --patience 2.11(2.00+0.10) 1.94(1.80+0.11) -8.1% Perhaps other platforms could also benefit. However it does NOT work on big-endian systems! [jc: minimum style and compilation fixes] Signed-off-by: Thomas Rast <trast@student.ethz.ch> Signed-off-by: Junio C Hamano <gitster@pobox.com>		2012-04-09 17:03:25 -07:00
..
xdiff.h	diff: add option to show whole functions as context	2011-10-10 12:05:07 -07:00
xdiffi.c	teach --histogram to diff	2011-07-12 09:29:20 -07:00
xdiffi.h	teach --histogram to diff	2011-07-12 09:29:20 -07:00
xemit.c	Merge branch 'rs/diff-postimage-in-context'	2012-01-29 13:18:55 -08:00
xemit.h
xhistogram.c	xdiff/xhistogram: drop need for additional variable	2011-08-08 13:00:17 -07:00
xinclude.h
xmacros.h	xdiff: cast arguments for ctype functions to unsigned char	2010-10-06 10:46:45 -07:00
xmerge.c	xdiff: cast arguments for ctype functions to unsigned char	2010-10-06 10:46:45 -07:00
xpatience.c	xdiff/xpatience: factor out fall-back-diff function	2011-07-07 09:41:24 -07:00
xprepare.c	Merge branch 'rs/diff-cleanup-records-fix'	2011-10-13 19:03:22 -07:00
xprepare.h
xtypes.h
xutils.c	xdiff: load full words in the inner loop of xdl_hash_record	2012-04-09 17:03:25 -07:00
xutils.h	xdiff/xprepare: use a smaller sample size for histogram diff	2011-07-12 09:30:00 -07:00