From: Peter Zijlstra <peterz@infradead.org>
To: Nicholas Piggin <npiggin@gmail.com>
Cc: Mel Gorman <mgorman@techsingularity.net>,
Linus Torvalds <torvalds@linux-foundation.org>,
Andrew Morton <akpm@linux-foundation.org>,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
Johannes Weiner <hannes@cmpxchg.org>, Jan Kara <jack@suse.cz>,
Rik van Riel <riel@redhat.com>, linux-mm <linux-mm@kvack.org>,
Will Deacon <will.deacon@arm.com>,
Paul McKenney <paulmck@linux.vnet.ibm.com>,
Alan Stern <stern@rowland.harvard.edu>
Subject: Re: page_waitqueue() considered harmful
Date: Thu, 29 Sep 2016 09:14:51 +0200 [thread overview]
Message-ID: <20160929071451.GI3318@worktop.controleur.wifipass.org> (raw)
In-Reply-To: <20160929164231.166d2910@roar.ozlabs.ibm.com>
On Thu, Sep 29, 2016 at 04:42:31PM +1000, Nicholas Piggin wrote:
> Take Alpha instead. It's using 32-bit ops.
Hmm, my Alpha docs are on the other machine, but I suppose the problem
is 64bit immediates (which would be a common problem I suppose, those
don't really work well on x86 either).
Yes, that does make it all more tricky than desired.
OTOH maybe this is a good excuse to (finally) sanitize the bitmap API to
use a fixed width. It using 'unsigned long' has been something of a pain
at times.
With that it would be 'obvious' bits need to be part of the same 32bit
word and we can use the normal smp_mb__{before,after}_atomic() again.
Given our bitops really are only about single bits, I can't see the
change making a real performance difference.
OTOH, the non atomic things like weight and ff[sz] do benefit from using
the longer words. Bother..
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next prev parent reply other threads:[~2016-09-29 7:15 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-09-26 20:58 Linus Torvalds
2016-09-26 21:23 ` Rik van Riel
2016-09-26 21:30 ` Linus Torvalds
2016-09-26 23:11 ` Kirill A. Shutemov
2016-09-27 1:01 ` Rik van Riel
2016-09-27 7:30 ` Peter Zijlstra
2016-09-27 8:54 ` Mel Gorman
2016-09-27 9:11 ` Kirill A. Shutemov
2016-09-27 9:42 ` Mel Gorman
2016-09-27 9:52 ` Minchan Kim
2016-09-27 12:11 ` Kirill A. Shutemov
2016-09-29 8:01 ` Peter Zijlstra
2016-09-29 12:55 ` Nicholas Piggin
2016-09-29 13:16 ` Peter Zijlstra
2016-09-29 13:54 ` Nicholas Piggin
2016-09-29 15:05 ` Rik van Riel
2016-09-27 8:03 ` Jan Kara
2016-09-27 8:31 ` Mel Gorman
2016-09-27 14:34 ` Peter Zijlstra
2016-09-27 15:08 ` Nicholas Piggin
2016-09-27 16:31 ` Linus Torvalds
2016-09-27 16:49 ` Peter Zijlstra
2016-09-28 10:45 ` Mel Gorman
2016-09-28 11:11 ` Peter Zijlstra
2016-09-28 16:10 ` Linus Torvalds
2016-09-29 13:08 ` Peter Zijlstra
2016-10-03 10:47 ` Mel Gorman
2016-09-27 14:53 ` Nicholas Piggin
2016-09-27 15:17 ` Nicholas Piggin
2016-09-27 16:52 ` Peter Zijlstra
2016-09-27 17:06 ` Nicholas Piggin
2016-09-28 7:05 ` Peter Zijlstra
2016-09-28 11:05 ` Paul E. McKenney
2016-09-28 11:16 ` Peter Zijlstra
2016-09-28 12:58 ` Paul E. McKenney
2016-09-29 1:31 ` Nicholas Piggin
2016-09-29 2:12 ` Paul E. McKenney
2016-09-29 6:21 ` Peter Zijlstra
2016-09-29 6:42 ` Nicholas Piggin
2016-09-29 7:14 ` Peter Zijlstra [this message]
2016-09-29 7:43 ` Peter Zijlstra
2016-09-28 7:40 ` Mel Gorman
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