From: Michal Hocko <mhocko@kernel.org>
To: Frank Mehnert <frank.mehnert@oracle.com>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: Re: Re: PG_reserved and compound pages
Date: Thu, 7 Apr 2016 17:22:35 +0200 [thread overview]
Message-ID: <20160407152234.GE32755@dhcp22.suse.cz> (raw)
In-Reply-To: <20567553.kUaGmfXpqH@noys2>
On Thu 07-04-16 15:45:02, Frank Mehnert wrote:
> On Wednesday 06 April 2016 17:33:43 Michal Hocko wrote:
[...]
> > Do you map your pages to the userspace? If yes then vma with VM_IO or
> > VM_PFNMAP should keep any attempt away from those pages.
>
> Yes, such memory objects are also mapped to userland. Do you think that
> VM_IO or VM_PFNMAP would guard against NUMA page migration?
Both auto numa and manual numa migration checks vma_migratable and that
excludes both VM flags.
> Because when
> NUMA page migration was introduced (I believe with Linux 3.8) I tested
> both flags and saw that they didn't prevent the migration on such VM
> areas. Maybe this changed in the meantime, do you have more information
> about that?
I haven't checked the history much but vma_migratable should be there
for quite some time. Maybe it wasn't used in the past. Dunno
> The drawback of at least VM_IO is that such memory is not part of a core
> dump.
that seems to be correct as per vma_dump_size
> Actually currently we use vm_insert_page() for userland mapping
> and mark the VM areas as
>
> VM_DONTEXPAND | VM_DONTDUMP
but that means that it won't end up in the dump either. Or am I missing
your point.
--
Michal Hocko
SUSE Labs
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next prev parent reply other threads:[~2016-04-07 15:22 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
2016-04-06 15:33 ` Michal Hocko
2016-04-07 13:45 ` Frank Mehnert
2016-04-07 15:22 ` Michal Hocko [this message]
2016-04-19 10:34 ` Frank Mehnert
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