Re: Re: High Activity of setprogname

[Christopher Faylor <cgf-use-the-mailinglist-please@cygwin.com>]

On Thu, May 19, 2011 at 01:41:47PM -0400, Ryan Johnson wrote:
>On 2:59 PM, Sravan Bhamidipati wrote:
>> Terminals like mintty and rxvt are doing an unusual amount of context
>> switching and consuming a lot of CPU cycles even in idle time. Process
>> Explorer suggests that this activity is largely attributable to
>> "cygwin1.dll!setprogname". Could this be something that should not or
>> need not be done? (Running cygwin.bat directly to use Cygwin doesn't
>> show such activity.)
>>
>> Most recently I've been seeing this behavior with Mintty v0.97, Cygwin
>> v1.7.9-1, Windows 7 Ultimate SP1 (x64, Build Version: 6.1.7601 Service
>> Pack 1 Build 7601). However I've noticed this in a few older versions
>> of Mintty, Cygwin as well, even on Windows XP.
>>
>> You can also view the mintty thread where this discussion began:
>> http://code.google.com/p/mintty/issues/detail?id=265
>The running code is related to select() (try running strace -mselect 
>mintty to see for yourself).
>
>A little poking around with windbg and gdb shows that select.cc:650 
>(thread_pipe) is the culprit: select itself is called with infinite 
>timeout; somebody more knowledgeable than me will have to explain why 
>thread_pipe would return data so often for an idle process, however.

It's called "polling", see:

http://msdn.microsoft.com/en-us/library/aa365779%28v=vs.85%29.aspx

cgf

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