On 07/10/2014 11:11 PM, Nicholas Nethercote wrote:
On Thu, Jul 10, 2014 at 10:34 PM, Patrick Walton <pcwal...@mozilla.com> wrote:
Historically, Rust's large stacks were due to the fact that at the time
stack growth was removed, rustc had worse codegen than it did today,
resulting in frames with very large activation records. Coupled with the
fact that rustc itself uses recursion heavily (probably too heavily), the
easiest thing to do was to give tasks large stacks by default. Perhaps this
decision should be revisited, as I think that it may well be the case that
rustc is going to be the exception, not the rule.
You can tune the size of stack growth when spawning a Rust task. Servo could
definitely use a stack size audit; I bet a ton of MBs can be shaved off with
some tuning.
"Large default stack size" doesn't seem to explain it.
I'd guess that the default is 2 MiB, because there are quite a few
entries in smaps like this:
7f54091fe000-7f54093fe000 rw-p 00000000 00:00 0
[stack:28143]
Size: 2048 kB
Rss: 12 kB
Pss: 12 kB
2 MiB has been allocated, but only a tiny amount has been touched and
is thus in RSS.
Here are the two biggest stacks:
7f540a700000-7f540b800000 rw-p 00000000 00:00 0
[stack:28139]
Size: 17408 kB
Rss: 7944 kB
Pss: 7944 kB
7f5409600000-7f540a400000 rw-p 00000000 00:00 0
[stack:28141]
Size: 14336 kB
Rss: 8192 kB
Pss: 8192 kB
For both, |Rss| is big and |Size| (equivalent to vsize) is even bigger.
Rust does have 2MB stacks by default. These giant numbers are surprising.
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