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List:       linux-kernel
Subject:    Re: [PATCH 5/10] mm/memcg: introduce page_relock_lruvec
From:       Hugh Dickins <hughd () google ! com>
Date:       2012-02-21 22:36:56
Message-ID: alpine.LSU.2.00.1202211426010.2012 () eggly ! anvils
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On Tue, 21 Feb 2012, KAMEZAWA Hiroyuki wrote:
> 
> No perforamce impact by replacing spin_lock_irq()/spin_unlock_irq() to
> spin_lock_irqsave() and spin_unlock_irqrestore() ?

None that I noticed - but that is not at all a reassuring answer!

It worries me a little.  I think it would make more or less difference
on different architectures, and I forget where x86 stands there - one
of the more or the less affected?  Worth branches down inside
page_relock_lruvec()?

It's also unfortunate to be "losing" the information of where _irq
is needed and where _irqsave (but not much gets lost with git).

It's something that can be fixed - and I think Konstantin's version
already keeps the variants: I just didn't want to get confused by them,
while focussing on the locking details.

Hugh
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