From: Charles Nutter <headius@...>
Date: 2013-04-17T11:31:21+09:00
Subject: [ruby-core:54376] Re: [ruby-trunk - Bug #8208] Raise cached exceptions for nonblocking IO to avoid allocation/stack-copying costs

On Apr 16, 2013, at 8:42 PM, Eric Wong <normalperson@yhbt.net> wrote:
> How does this compare to an implementation which returns symbols
> like :wait_*able instead of raising exceptions?

It will be more expensive, but mostly because exception-handling has a fair amount of overhead even with a cached exception object. I suggest this mostly because it may be considered less invasive than adding new APIs.

>> The benefit of this change would be that nonblocking IO has zero
>> wasted overhead. The down side would be that the exceptions raised do
>> not have a useful backtrace unless debug or verbose.
> 
> Exceptions for nonblocking I/O still makes --debug too noisy.

Indeed!

> I still think it's better to push for an exception-less API for common
> errors.  EAGAIN/EINPROGRESS/EWOULDBLOCK are far too common (and not
> reasonably avoidable) to be considered exceptions.

Agreed�but that hasn't happened yet. I'm hedging my bets :-)

Which issue is tracking an exceptionless nonblocking API? Maybe we can nudge it forward.

- Charlie