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authorLibravatar Colin Stolley <cstolley@runbox.com>2019-11-27 16:24:53 -0600
committerLibravatar Junio C Hamano <gitster@pobox.com>2019-12-03 07:59:45 -0800
commitec48540fe8c387cf7424d5387ddbd53e89bb9d51 (patch)
tree1b2111770e24c35a2591d4458c6c6e3fba124e8b /t/t4214-log-graph-octopus.sh
parentThe first batch post 2.24 cycle (diff)
downloadtgif-ec48540fe8c387cf7424d5387ddbd53e89bb9d51.tar.xz
packfile.c: speed up loading lots of packfiles
When loading packfiles on start-up, we traverse the internal packfile list once per file to avoid reloading packfiles that have already been loaded. This check runs in quadratic time, so for poorly maintained repos with a large number of packfiles, it can be pretty slow. Add a hashmap containing the packfile names as we load them so that the average runtime cost of checking for already-loaded packs becomes constant. Add a perf test to p5303 to show speed-up. The existing p5303 test runtimes are dominated by other factors and do not show an appreciable speed-up. The new test in p5303 clearly exposes a speed-up in bad cases. In this test we create 10,000 packfiles and measure the start-up time of git rev-parse, which does little else besides load in the packs. Here are the numbers for the new p5303 test: Test HEAD^ HEAD --------------------------------------------------------------------- 5303.12: load 10,000 packs 1.03(0.92+0.10) 0.12(0.02+0.09) -88.3% Signed-off-by: Colin Stolley <cstolley@runbox.com> Helped-by: Jeff King <peff@peff.net> [jc: squashed the change to call hashmap in install_packed_git() by peff] Signed-off-by: Junio C Hamano <gitster@pobox.com>
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