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由 Nicolas Pitre 提交于
When the delta data is cached in memory until it is written to a pack file on disk, it is best to compress it right away in find_deltas() for the following reasons: - we have to compress that data anyway; - this allows for caching more deltas with the same cache size limit; - compression is potentially threaded. This last point is especially relevant for SMP run time. For example, repacking the Linux repo on a quad core processor using 4 threads with all default settings produce the following results before this change: real 2m27.929s user 4m36.492s sys 0m3.091s And with this change applied: real 2m13.787s user 4m37.486s sys 0m3.159s So the actual execution time stayed more or less the same but the wall clock time is shorter. This is however not a good thing to do when generating a pack for network transmission. In that case, the network is most likely to throttle the data throughput, so it is best to make find_deltas() faster in order to start writing data ASAP since we can afford spending more time between writes to compress the data at that point. Signed-off-by: NNicolas Pitre <nico@cam.org> Signed-off-by: NJunio C Hamano <gitster@pobox.com>
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