sha1_file: don't malloc the whole compressed result when writing out objects
There is no real advantage to malloc the whole output buffer and deflate the data in a single pass when writing loose objects. That is like only 1% faster while using more memory, especially with large files where memory usage is far more. It is best to deflate and write the data out in small chunks reusing the same memory instead. For example, using 'git add' on a few large files averaging 40 MB ... Before: 21.45user 1.10system 0:22.57elapsed 99%CPU (0avgtext+0avgdata 0maxresident)k 0inputs+828040outputs (0major+142640minor)pagefaults 0swaps After: 21.50user 1.25system 0:22.76elapsed 99%CPU (0avgtext+0avgdata 0maxresident)k 0inputs+828040outputs (0major+104408minor)pagefaults 0swaps While the runtime stayed relatively the same, the number of minor page faults went down significantly. Signed-off-by: NNicolas Pitre <nico@fluxnic.net> Signed-off-by: NJunio C Hamano <gitster@pobox.com>
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