linux-kernel - Re: Keys get stuck

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Date:	Thu, 13 Mar 2008 15:18:10 +0100
From:	Helge Hafting <helge.hafting@...el.hist.no>
To:	Mike Galbraith <efault@....de>, Jan Knutar <jk-lkml@....fi>,
	linux-kernel@...r.kernel.org, Hans-Peter Jansen <hpj@...la.net>,
	Jiri Kosina <jkosina@...e.cz>,
	David Newall <davidn@...idnewall.com>,
	Theodore Tso <tytso@....edu>, "Fred ." <eldmannen@...il.com>
Subject: Re: Keys get stuck

Carlos R. Mafra wrote:
> On Thu 13.Mar'08 at 12:28:13 +0100, Mike Galbraith wrote:
>   
>> [...]
>> Swap can definitely keep X off the cpu for extended periods,
>> [...]
>>     
>
> So I would like to ask if swap letting X (and everything else
> in my experience) out of the cpu for extended periods is
> considered normal behaviour, in the sense that nobody is
> trying to "fix" it (due to it being considered impossible
> to fix)...?
>   
Yes, this is perfectly normal. A heavily swapping machine
will swap out parts of X.

Now, if X has a need for low-latency for keyboard handling,
then the X developers can use mlock to lock
the X keyboard service in memory, and make it a real-time
(or at least high priority) process too.  This should
avoid the problem even with extreme swapping and/or
high cpu load.

> Sorry for being off-topic, but I run a minimal Window Maker
> desktop in a P4 3.0 GHz with 512 MB of RAM (around 140 MB
> being used as per 'free'), and trying to load a 380 MB text
> file in xjed editor makes my whole desktop quite unfair...
> it takes tens of seconds to switch desktop, type things in
> the terminal etc. 
>
>   
Seems ou use too much memory then. If xjed
wastes memory (by bringing the entire file into memory
in one go) then you'll get some swapping.

> When xjed finishes loading the text file, everything comes
> back to "fair" again.
>
> Is there some law in the nature of computers which says
> that when swapping everything else waits for swap to finish 
> its business? I hope not :-)
>   
No such law, but there are badly implemented software
around. If xjed is capable of delaying all X events while
loading the file, for example . . .

Helge Hafting
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