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authorLibravatar Taylor Blau <me@ttaylorr.com>2021-08-31 16:52:48 -0400
committerLibravatar Junio C Hamano <gitster@pobox.com>2021-09-01 13:56:43 -0700
commit2d595973330765aca43bd4809c55ac0e66e7236f (patch)
tree65e2e2b20a8a1f787cdad36d5735c29db15e4512 /csum-file.c
parentp5310: extract full and partial bitmap tests (diff)
downloadtgif-2d595973330765aca43bd4809c55ac0e66e7236f.tar.xz
p5326: perf tests for MIDX bitmaps
These new performance tests demonstrate effectively the same behavior as p5310, but use a multi-pack bitmap instead of a single-pack one. Notably, p5326 does not create a MIDX bitmap with multiple packs. This is so we can measure a direct comparison between it and p5310. Any difference between the two is measuring just the overhead of using MIDX bitmaps. Here are the results of p5310 and p5326 together, measured at the same time and on the same machine (using a Xenon W-2255 CPU): Test HEAD ------------------------------------------------------------------------ 5310.2: repack to disk 96.78(93.39+11.33) 5310.3: simulated clone 9.98(9.79+0.19) 5310.4: simulated fetch 1.75(4.26+0.19) 5310.5: pack to file (bitmap) 28.20(27.87+8.70) 5310.6: rev-list (commits) 0.41(0.36+0.05) 5310.7: rev-list (objects) 1.61(1.54+0.07) 5310.8: rev-list count with blob:none 0.25(0.21+0.04) 5310.9: rev-list count with blob:limit=1k 2.65(2.54+0.10) 5310.10: rev-list count with tree:0 0.23(0.19+0.04) 5310.11: simulated partial clone 4.34(4.21+0.12) 5310.13: clone (partial bitmap) 11.05(12.21+0.48) 5310.14: pack to file (partial bitmap) 31.25(34.22+3.70) 5310.15: rev-list with tree filter (partial bitmap) 0.26(0.22+0.04) versus the same tests (this time using a multi-pack index): Test HEAD ------------------------------------------------------------------------ 5326.2: setup multi-pack index 78.99(75.29+11.58) 5326.3: simulated clone 11.78(11.56+0.22) 5326.4: simulated fetch 1.70(4.49+0.13) 5326.5: pack to file (bitmap) 28.02(27.72+8.76) 5326.6: rev-list (commits) 0.42(0.36+0.06) 5326.7: rev-list (objects) 1.65(1.58+0.06) 5326.8: rev-list count with blob:none 0.26(0.21+0.05) 5326.9: rev-list count with blob:limit=1k 2.97(2.86+0.10) 5326.10: rev-list count with tree:0 0.25(0.20+0.04) 5326.11: simulated partial clone 5.65(5.49+0.16) 5326.13: clone (partial bitmap) 12.22(13.43+0.38) 5326.14: pack to file (partial bitmap) 30.05(31.57+7.25) 5326.15: rev-list with tree filter (partial bitmap) 0.24(0.20+0.04) There is slight overhead in "simulated clone", "simulated partial clone", and "clone (partial bitmap)". Unsurprisingly, that overhead is due to using the MIDX's reverse index to map between bit positions and MIDX positions. This can be reproduced by running "git repack -adb" along with "git multi-pack-index write --bitmap" in a large-ish repository. Then run: $ perf record -o pack.perf git -c core.multiPackIndex=false \ pack-objects --all --stdout >/dev/null </dev/null $ perf record -o midx.perf git -c core.multiPackIndex=true \ pack-objects --all --stdout >/dev/null </dev/null and compare the two with "perf diff -c delta -o 1 pack.perf midx.perf". The most notable results are below (the next largest positive delta is +0.14%): # Event 'cycles' # # Baseline Delta Shared Object Symbol # ........ ....... .................. .......................... # +5.86% git [.] nth_midxed_offset +5.24% git [.] nth_midxed_pack_int_id 3.45% +0.97% git [.] offset_to_pack_pos 3.30% +0.57% git [.] pack_pos_to_offset +0.30% git [.] pack_pos_to_midx Signed-off-by: Taylor Blau <me@ttaylorr.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
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