send-pack: set core.warnAmbiguousRefs=false #68
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Submitted as pull.68.git.gitgitgadget@gmail.com |
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Submitted as pull.68.v2.git.gitgitgadget@gmail.com |
A git push process runs several processes during its run, but one includes git send-pack which calls git pack-objects and passes the known have/wants into stdin using object ids. However, the default setting for core.warnAmbiguousRefs requires git pack-objects to check for ref names matching the ref_rev_parse_rules array in refs.c. This means that every object is triggering at least six "file exists?" queries. When there are a lot of refs, this can add up significantly! I observed a simple push spending three seconds checking these paths. The fix here is similar to 4c30d50 "rev-list: disable object/refname ambiguity check with --stdin". While the get_object_list() method reads the objects from stdin, turn warn_on_object_refname_ambiguity flag (which is usually true) to false. Just for code hygiene, save away the original at the beginning and restore it once we are done. Helped-by: Jeff King <peff@peff.net> Signed-off-by: Derrick Stolee <dstolee@microsoft.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
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I made the mistake of hitting the "Merge" button... But this patch made it upstream, as a4544b3 |
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I've been looking into the performance of
git pushfor very large repos. Our users are reporting that 60-80% ofgit pushtime is spent during the "Enumerating objects" phase ofgit pack-objects.A
git pushprocess runs several processes during its run, but one includesgit send-packwhich callsgit pack-objectsand passes the known have/wants intostdinusing object ids. However, the default setting forcore.warnAmbiguousRefsrequiresgit pack-objectsto check for ref names matching theref_rev_parse_rulesarray inrefs.c. This means that every object is triggering at least six "file exists?" queries.When there are a lot of refs, this can add up significantly! My PerfView trace for a simple push measured 3 seconds spent checking these paths.
The fix is to set the global
warn_on_object_refname_ambiguityto 0 for the section that is performing these object reads.In addition to this patch submission, we are looking into merging it into our fork sooner [1].
[1] microsoft#67
Changes in V2: Instead of using the "-c" flag from send-pack, just set the global. I left the name of the cover letter the same to not confuse anyone viewing the message without threading.
Cc: peff@peff.net