Junio C Hamano <gitster@xxxxxxxxx> writes: > Nguyễn Thái Ngọc Duy <pclouds@xxxxxxxxx> writes: > >> Current code makes pack-objects always do check_pack_crc() in >> unpack_entry() even if right after that we find out there's a cached >> version and pack access is not needed. Swap two code blocks, search >> for cached version first, then check crc. [...] > > Interesting. > > This is only triggered inside pack-objects, which would read a lot > of data from existing packs, and the overhead for looking up the > entry from the revindex, faulting in the actual packdata, and > computing and comparing the crc would not be trivial, especially as > the cost is incurred over many objects we need to untangle in the > delta chain. If you have interesting numbers to show how much this > improves the performance, I am curious to see it. I can't see anything wrong with the patch, but then I haven't stared too hard. (It seems that my conversion around abe601b (sha1_file: remove recursion in unpack_entry, 2013-03-27) was faithful on this point, the problem has existed for longer than that.) I tried the perf script below, but at least for the git repo the only thing I can see is noise. --- 8< --- t/perf/p5300-pack-object.sh --- 8< --- #!/bin/sh test_description="Tests object packing performance" . ./perf-lib.sh test_perf_default_repo test_perf 'pack-objects on commits in HEAD' ' git rev-list HEAD | git pack-objects --stdout >/dev/null ' test_perf 'pack-objects on all of HEAD' ' git rev-list --objects HEAD | git pack-objects --stdout >/dev/null ' test_done -- To unsubscribe from this list: send the line "unsubscribe git" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html