From: Frank Mehnert <frank.mehnert@oracle.com>
To: Michal Hocko <mhocko@kernel.org>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: Re: PG_reserved and compound pages
Date: Wed, 06 Apr 2016 17:12:43 +0200 [thread overview]
Message-ID: <3877205.TjDYue2aah@noys2> (raw)
In-Reply-To: <20160406150206.GB24283@dhcp22.suse.cz>
Hi Michal,
On Wednesday 06 April 2016 17:02:06 Michal Hocko wrote:
> [CCing linux-mm mailing list]
>
> On Wed 06-04-16 13:28:37, Frank Mehnert wrote:
> > Hi,
> >
> > Linux 4.5 introduced additional checks to ensure that compound pages are
> > never marked as reserved. In our code we use PG_reserved to ensure that
> > the kernel does never swap out such pages, e.g.
>
> Are you putting your pages on the LRU list? If not how they could get
> swapped out?
No, we do nothing like that. It was my understanding that at least with
older kernels it was possible that pages allocated with alloc_pages()
could be swapped out or otherwise manipulated, I might be wrong. For
instance, it's also necessary that the physical address of the page
is known and that it does never change. I know, there might be problems
with automatic NUMA page migration but that's another story.
> > int i;
> > struct page *pages = alloc_pages(GFP_HIGHUSER | __GFP_COMP, 4);
> > for (i = 0; i < 16; i++)
> >
> > SetPageReserved(&pages[i]);
> >
> > The purpose of setting PG_reserved is to prevent the kernel from swapping
> > this memory out. This worked with older kernel but not with Linux 4.5 as
> > setting PG_reserved to compound pages is not allowed any more.
> >
> > Can somebody explain how we can achieve the same result in accordance to
> > the new Linux 4.5 rules?
Frank
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next prev parent reply other threads:[~2016-04-06 15:12 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <4482994.u2S3pScRyb@noys2>
2016-04-06 15:02 ` Michal Hocko
2016-04-06 15:12 ` Frank Mehnert [this message]
2016-04-06 15:33 ` Michal Hocko
2016-04-07 13:45 ` Frank Mehnert
2016-04-07 15:22 ` Michal Hocko
2016-04-19 10:34 ` Frank Mehnert
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