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while loop and CPU ..


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Old Unix and Linux 08-27-2008
nivea_jmd nivea_jmd is offline
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while loop and CPU ..

Hello frnds..

i m using while loops in my code.. bec of that my application uses almost 90% of CPU resources.. its not lettin others applications to run..

actually i have to read some signal from serial port... n till i dont get it high or low..
i have to read that signal continuously... its for this reason i m using while loops.

else if(status==0)

some code


someone suggested me to use sleep in the while loop..
i cant use it bec we are workin on realtime systems...
so we usually avoid using delay n sleep....

can anyone help me on this ???

my application is on C++/fedora
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Old Unix and Linux 08-27-2008
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The standard call is select(). Do a "man 2 select". It's a little difficult to understand at first, and maybe you have only one file descriptor to wait on, so you can do a man on poll(), but it's not portable to older UNIX's. Here, you can do:

struct pollfd pollfd_list[] = { 0 /*stdin */, ~0 /* all events */, 0 };
poll( pollfd_list, 1 /* 1 file descriptor */, 1000 /* 1 second */ );

This will return at the latest every second (unless your process is pushed out due to other processes -- Linux isn't realtime) and whether or not you have something to do depends on the last field in pollfd_list.
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