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Sender: Minchan Kim <minchan.kim@gmail.com>
Date:   Wed, 17 Feb 2021 13:32:05 -0800
From:   Minchan Kim <minchan@kernel.org>
To:     Matthew Wilcox <willy@infradead.org>
Cc:     Michal Hocko <mhocko@suse.com>,
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Subject: Re: [RFC 1/2] mm: disable LRU pagevec during the migration
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On Wed, Feb 17, 2021 at 09:16:12PM +0000, Matthew Wilcox wrote:
> On Wed, Feb 17, 2021 at 12:46:19PM -0800, Minchan Kim wrote:
> > > I suspect you do not want to add atomic_read inside hot paths, right? Is
> > > this really something that we have to microoptimize for? atomic_read is
> > > a simple READ_ONCE on many archs.
> > 
> > It's also spin_lock_irq_save in some arch. If the new synchonization is
> > heavily compilcated, atomic would be better for simple start but I thought
> > this locking scheme is too simple so no need to add atomic operation in
> > readside.
> 
> What arch uses a spinlock for atomic_read()?  I just had a quick grep and
> didn't see any.

Ah, my bad. I was confused with update side.
Okay, let's use atomic op to make it simple.

Thanks for the review, Mattew and Michal.