File cache entries are read in 10k chunks

[jeffkaufman]

We could use a stat and read whole files at once, but currently we read files in fixed size chunks. Since we need the whole file in memory, this is pretty wasteful.

[jeffkaufman]

Fixed in 56e4c8d

[keesspoelstra]

What about side effects/behavior with RewriteLevel PassThrough?

[jeffkaufman]

@keesspoelstra Huh? I wouldn't expect 56e4c8d to affect passthrough, because that shouldn't be using the file cache at all.

[keesspoelstra]

Wrong issue, should be a remark for 973, sorry