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From: Robert Schedel <r.schedel@yahoo.de>
To: linux-dvb@linuxtv.org
Subject: Re: [linux-dvb] High CPU load in "top" due to budget_av slot polling
Date: Thu, 17 Apr 2008 17:27:54 +0200	[thread overview]
Message-ID: <48076C7A.7070901@yahoo.de> (raw)
In-Reply-To: <48066F62.8000709@yahoo.de>

Robert Schedel wrote:

> Is the 250ms timeout an approved limit? Decreasing it would push the
> load further down. Probably it still has to cover slow CAMs as well as a
> stressed PCI bus. Unfortunately, without CAM/CI I cannot make any
> statements myself.

Just got another idea to improve the code: Function 
"saa7146_wait_for_debi_done_sleep" could be reworked to use what is 
known as "truncated binary exponential backoff" algorithm. IOW, on each 
sleep duplicate the period from 1ms until a fixed maximum, e.g. 32ms. 
This way polling ends fast for those users with fast bus/CAM, and those 
requiring 200ms due to slow bus/CAM should not worry about e.g. 216ms 
response time.

My first tests look promising (load goes down to 0). However, is not the 
simple BEB algorithm already patented?

Regards,
Robert


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  parent reply	other threads:[~2008-04-17 17:32 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-04-07  9:29 [linux-dvb] High CPU load in "top" due to budget_av slot polling Robert Schedel
2008-04-08  7:26 ` Robert Schedel
2008-04-12  0:11   ` Oliver Endriss
2008-04-11 23:00 ` Oliver Endriss
2008-04-16 21:28   ` Robert Schedel
2008-04-17 11:12     ` Guy Martin
2008-04-17 15:27     ` Robert Schedel [this message]
2008-04-18  0:34       ` Oliver Endriss
2008-04-20 19:12         ` Robert Schedel
2008-04-18  1:21     ` Oliver Endriss
2008-04-18  2:44       ` hermann pitton
2008-04-20 19:43       ` Robert Schedel
2008-04-20 23:25         ` Oliver Endriss

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