netdev - Re: [Lsf] [LSF/MM TOPIC] Generic page-pool recycle facility?

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Date:	Mon, 11 Apr 2016 14:27:40 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Jesper Dangaard Brouer <brouer@...hat.com>
Cc:	lsf@...ts.linux-foundation.org, Tom Herbert <tom@...bertland.com>,
	Brenden Blanco <bblanco@...mgrid.com>,
	James Bottomley <James.Bottomley@...senPartnership.com>,
	linux-mm <linux-mm@...ck.org>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	lsf-pc@...ts.linux-foundation.org,
	Alexei Starovoitov <alexei.starovoitov@...il.com>
Subject: Re: [Lsf] [LSF/MM TOPIC] Generic page-pool recycle facility?

On Mon, 2016-04-11 at 22:23 +0200, Jesper Dangaard Brouer wrote:

> If we have a page-pool recycle facility, then we could use the trick,
> right? (As we know that get_page_unless_zero() cannot happen for pages
> in the pool).

Well, if you disable everything that possibly use
get_page_unless_zero(), I guess this could work.

But then, you'll have to spy lkml traffic forever to make sure no new
feature is added in the kernel, using this get_page_unless_zero() in a
new clever way.

You could use a page flag so that z BUG() triggers if
get_page_unless_zero() is attempted on one of your precious pages ;)\

We had very subtle issues before my fixes (check
35b7a1915aa33da812074744647db0d9262a555c and children), so I would not
waste time on the lock prefix avoidance at this point.