xwin-xdg-menu high cpu usage with rxvt-unicode

[Jon Turney]

On 23/06/2021 04:08, Takashi Yano wrote:
> On Mon, 21 Jun 2021 05:49:28 +0000
> Viet-Duc Le wrote:
>> Hi,
>>
>> I've encountered a peculiar issue with rxvt-unicode launched from xwin-xdg-menu (20170321-1)
>> The image below corresponds to two rxvt-unicode instances, each occupies 30% of system resouce.
>> https://imgur.com/a/FTFwIrZ
>> I'm using the the latest version of cygwin. 'cygcheck.out' is attached per guideline.
>>
>> Steps to reproduce:
>> - Start XWin Server from Start menu
>> - X applications menu -> System Tools -> rxvt-unicode
>> - Kill rxvt-unicode to free the resource again
>>
>> Other observations:
>> - XTerm does not incur high resources.
>> - Manually launching rxvt-unicode from XTerm does not incur high resources.
>>
>> I think this is not an issue with rxvt but with xwin-xdg-menu.
>> On laptop, it is very noticeable when the fan kicks in.
>> Insights and suggestions are much appreciated.
>>
>> Thanks.
>> Viet-Duc
> 
> I looked into this problem and found the cause.
> urxvt seems to close stdout while xwin-xdg-menu use select()
> to read stdout of the launched apps. Since stdout is closed,
> select() returns repeatedly without any output. This causes
> high cpu load.
> 
> I also confirmed that the following patch for xwin-xdg-menu
> resolves the issue.
> 
[...]
> 
> Jon, could you please have a look?

Thanks very much for looking into this, and the patch.

That looks right.

I applied the patch, and built and uploaded a xwin-xdg-menu-20210623-1 
test package.

Perhaps you could try that, and see if it improves things for you?

(Similar code is used in XWin, so I also need to make a similar change 
there)