This is caused by StrVector having a generic implementation for &[S]
and so #5898 means that method resolution of ~[~[1]].concat() sees that
both StrVector and VectorVector have methods that (superficially) match.
They are now connect_vec and concat_vec, which means that they can actually be
called.
r? @brson
links to issues: #7065 the race that's fixed; #7066 the perf improvement I added. There are also some minor cleanup commits here.
To measure the performance improvement from replacing the exclusive with an atomic uint, I edited the ```msgsend-ring-rw-arcs``` bench test to do a ```write_downgrade``` instead of just a ```write```, so that it stressed the code paths that accessed ```read_count```. (At first I was still using ```write``` and saw no performance difference whatsoever, whoooops.)
The bench test measures how long it takes to send 1,000,000 messages by using rwarcs to emulate pipes. I also measured the performance difference imposed by the fix to the ```access_lock``` race (which involves taking an extra semaphore in the ```cond.wait()``` path). The net result is that fixing the race imposes a 4% to 5% slowdown, but doing the atomic uint optimization gives a 6% to 8% speedup.
Note that this speedup will be most visible in read- or downgrade-heavy workloads. If an RWARC's only users are writers, the optimization doesn't matter. All the same, I think this more than justifies the extra complexity I mentioned in #7066.
The raw numbers are:
```
with xadd read count
before write_cond fix
4.18 to 4.26 us/message
with write_cond fix
4.35 to 4.39 us/message
with exclusive read count
before write_cond fix
4.41 to 4.47 us/message
with write_cond fix
4.65 to 4.76 us/message
```
This is caused by StrVector having a generic implementation for &[S]
and so #5898 means that method resolution of ~[~[1]].concat() sees that
both StrVector and VectorVector have methods that (superficially) match.
They are now connect_vec and concat_vec, which means that they can actually be
called.
This is supposed to be an efficient way to link the lifetimes
of tasks into a tree. JoinLatches form a tree and when `release`
is called they wait on children then signal the parent.
This structure creates zombie tasks which currently keep the entire
task allocated. Zombie tasks are supposed to be tombstoned but that
code does not work correctly.
This fixes the strange random crashes in compile-fail tests.
This reverts commit 96cd61ad034cc9e88ab6a7845c3480dbc1ea62f3.
Conflicts:
src/librustc/driver/driver.rs
src/libstd/str.rs
src/libsyntax/ext/quote.rs
I would appreciate if someone could help out with the Windows code on this pull request. I tried to test it using WINE but I couldn't figure out a way to set that up.
