Re: + kmap-types-clean-up-and-optimization.patch added to -mm tree

Previous thread: [PATCH v3 0/4] MFD MAX8998/LP3974 Driver Update by MyungJoo Ham on Thursday, December 23, 2010 - 1:53 am. (12 messages)

Next thread: 2.6.37-rc7: no more shutdown on DELL E6400 by Eric Valette on Thursday, December 23, 2010 - 2:55 am. (5 messages)
From: Peter Zijlstra
Date: Thursday, December 23, 2010 - 2:58 am

NO! That's wrong, in fact non of them are being used, but removing them
will decrease the number of kmap_atomic slots, but those are still being

Feh, its only a few pages and since there is no way to actually tell if
you've got enough kmap atomic pages other than experiencing runtime

Nacked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
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From: Jan Beulich
Date: Thursday, December 23, 2010 - 3:47 am

Would you mind pointing out examples of such uses (i.e. without
the proper enumerator)? How would those avoid collisions with

Whether 2Mb of lowmem is "only a few pages" certainly depends
on the perspective you take.

And even then - shouldn't the bad (non-enumerated) uses of
atomic kmap-s be fixed rather than keeping unused entries in
the enumeration just because there is broken code somewhere?

Jan

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From: Peter Zijlstra
Date: Thursday, December 23, 2010 - 3:56 am

Nobody uses explicit slots anymore:

/*
 * Make both: kmap_atomic(page, idx) and kmap_atomic(page) work.
 */
#define kmap_atomic(page, args...) __kmap_atomic(page)

All instances of KM_foo are deprecated and in need of a cleanup.

With the current 20 slots on x86, its 80k per CPU, you need 25 CPUs to
cross the 2M boundary, 32bit kernels having that many CPUs deserve to
suffer.


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Previous thread: [PATCH v3 0/4] MFD MAX8998/LP3974 Driver Update by MyungJoo Ham on Thursday, December 23, 2010 - 1:53 am. (12 messages)

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