Cache file contents in the session(s)

[birkenfeld]

This series of commits makes an attempt to avoid re-reading files from disk over and over. It also makes all Session access use a Rc pointer, so that the session isn't cloned for every match.

This gives a large speedup in debug mode (doing racer complete std::io:: drops from 1.14s to 0.48s on my machine), probably because the BufReader implementation is really slow when unoptimized.

In a release build I get a ~25% speedup from 30ms to 22ms using kbknapp's method from here: https://gist.github.com/kbknapp/fb28a49d7a0fe8b8e400 - allocations are down from from 82k (19M bytes) to 56k (7M bytes).

In daemon mode every request creates its own root Session, so files are not cached. This is probably a good thing as long as the cache is never invalidated e.g. based on mtime.

[birkenfeld]

(updated benchmark numbers in description)

[dleslie]

As a person who codes on a slower machine, allow me to say thank-you.

On Wed, Aug 26, 2015 at 10:18 AM, Georg Brandl notifications@github.com
wrote:

(updated benchmark numbers in description)

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#364 (comment).

[phildawes]

Awesome, thanks @birkenfeld! Have merged.

BTW, I might be wrong but I don't think the session needs to be returned in the match object, I think it was just convenience when @damienrg added the Session to handle temporary file translation.

If instead we passed the session as a parameter to all calls then we wouldn't need RC/RefCell because mutable borrows would suffice. Does that sound correct to you?

Cheers!

[birkenfeld]

@phildawes so there is basically no reason to have multiple Session objects? If so, that can simplify the matter a lot.

[birkenfeld]

We'll likely still need the RefCell for the file cache, since using a mutable borrow is going to be very unpleasant - many of the functions make liberal use of multiple borrowing.