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d4316604f8
Enabling pack.writebitmaphashcache should always be a performance win. It costs only 4 bytes per object on disk, and the timings inae4f07fbcc(pack-bitmap: implement optional name_hash cache, 2013-12-21) show it improving fetch and partial-bitmap clone times by 40-50%. The only reason we didn't enable it by default at the time is that early versions of JGit's bitmap reader complained about the presence of optional header bits it didn't understand. But that was changed in JGit's d2fa3987a (Use bitcheck to check for presence of OPT_FULL option, 2013-10-30), which made it into JGit v3.5.0 in late 2014. So let's turn this option on by default. It's backwards-compatible with all versions of Git, and if you are also using JGit on the same repository, you'd only run into problems using a version that's almost 5 years old. We'll drop the manual setting from all of our test scripts, including perf tests. This isn't strictly necessary, but it has two advantages: 1. If the hash-cache ever stops being enabled by default, our perf regression tests will notice. 2. We can use the modified perf tests to show off the behavior of an otherwise unconfigured repo, as shown below. These are the results of a few of a perf tests against linux.git that showed interesting results. You can see the expected speedup in 5310.4, which was noted inae4f07fbcc. Curiously, 5310.8 did not improve (and actually got slower), despite seeing the opposite inae4f07fbcc. I don't have an explanation for that. The tests from p5311 did not exist back then, but do show improvements (a smaller pack due to better deltas, which we found in less time). Test HEAD^ HEAD ------------------------------------------------------------------------------------- 5310.4: simulated fetch 7.39(22.70+0.25) 5.64(11.43+0.22) -23.7% 5310.8: clone (partial bitmap) 18.45(24.83+1.19) 19.94(28.40+1.36) +8.1% 5311.31: server (128 days) 0.41(1.13+0.05) 0.34(0.72+0.02) -17.1% 5311.32: size (128 days) 7.4M 7.0M -4.8% 5311.33: client (128 days) 1.33(1.49+0.06) 1.29(1.37+0.12) -3.0% Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
45 lines
1.1 KiB
Bash
Executable file
45 lines
1.1 KiB
Bash
Executable file
#!/bin/sh
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test_description='performance of fetches from bitmapped packs'
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. ./perf-lib.sh
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test_perf_default_repo
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test_expect_success 'create bitmapped server repo' '
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git config pack.writebitmaps true &&
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git repack -ad
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'
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# simulate a fetch from a repository that last fetched N days ago, for
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# various values of N. We do so by following the first-parent chain,
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# and assume the first entry in the chain that is N days older than the current
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# HEAD is where the HEAD would have been then.
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for days in 1 2 4 8 16 32 64 128; do
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title=$(printf '%10s' "($days days)")
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test_expect_success "setup revs from $days days ago" '
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now=$(git log -1 --format=%ct HEAD) &&
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then=$(($now - ($days * 86400))) &&
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tip=$(git rev-list -1 --first-parent --until=$then HEAD) &&
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{
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echo HEAD &&
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echo ^$tip
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} >revs
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'
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test_perf "server $title" '
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git pack-objects --stdout --revs \
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--thin --delta-base-offset \
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<revs >tmp.pack
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'
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test_size "size $title" '
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wc -c <tmp.pack
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'
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test_perf "client $title" '
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git index-pack --stdin --fix-thin <tmp.pack
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'
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done
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test_done
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