archive/zip: reading many small files allocates a lot of memory

[dziemba]

archive/zip creates a new compress/flate.Reader for each file read from the archive. If there are many small files in an archive, this allocates a lot of memory.

compress/flate allows re-using of Readers, see https://codereview.appspot.com/97140043/

Using this in archive/zip reduces the amount of memory allocated/GCed. In a real-world scenario when reading ~ 500 small files from a ZIP archive this gives a speedup of 1.5x-2x.

Version: go1.6rc2

[dziemba]

This should fix it: https://go-review.googlesource.com/#/c/19416/

But I'm not 100% sure if the implementaion is correct. Please review with care ;)

[gopherbot]

CL https://golang.org/cl/19416 mentions this issue.

[dziemba]

Can we merge this soon so it will be included in Go 1.7?