From: Jason Gunthorpe <jgg@ziepe.ca>
To: Ira Weiny <ira.weiny@intel.com>
Cc: Daniel Jordan <daniel.m.jordan@oracle.com>,
akpm@linux-foundation.org, dave@stgolabs.net, jack@suse.cz,
cl@linux.com, linux-mm@kvack.org, kvm@vger.kernel.org,
kvm-ppc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
linux-fpga@vger.kernel.org, linux-kernel@vger.kernel.org,
alex.williamson@redhat.com, paulus@ozlabs.org,
benh@kernel.crashing.org, mpe@ellerman.id.au, hao.wu@intel.com,
atull@kernel.org, mdf@kernel.org, aik@ozlabs.ru
Subject: Re: [PATCH 0/5] use pinned_vm instead of locked_vm to account pinned pages
Date: Thu, 14 Feb 2019 13:12:31 -0700 [thread overview]
Message-ID: <20190214201231.GC1739@ziepe.ca> (raw)
In-Reply-To: <20190214193352.GA7512@iweiny-DESK2.sc.intel.com>
On Thu, Feb 14, 2019 at 11:33:53AM -0800, Ira Weiny wrote:
> > I think it had to do with double accounting pinned and mlocked pages
> > and thus delivering a lower than expected limit to userspace.
> >
> > vfio has this bug, RDMA does not. RDMA has a bug where it can
> > overallocate locked memory, vfio doesn't.
>
> Wouldn't vfio also be able to overallocate if the user had RDMA pinned pages?
Yes
> I think the problem is that if the user calls mlock on a large range then both
> vfio and RDMA could potentially overallocate even with this fix. This was your
> initial email to Daniel, I think... And Alex's concern.
Here are the possibilities
- mlock and pin on the same pages - RDMA respects the limit, VFIO halfs it.
- mlock and pin on different pages - RDMA doubles the limit, VFIO
respects it
- VFIO and RDMA in the same process, the limit is halfed or doubled, depending.
IHMO we should make VFIO & RDMA the same, and then decide what to do
about case #2.
> > Really unclear how to fix this. The pinned/locked split with two
> > buckets may be the right way.
>
> Are you suggesting that we have 2 user limits?
This is what RDMA has done since CL's patch.
It is very hard to fix as you need to track how many pages are mlocked
*AND* pinned.
Jason
next prev parent reply other threads:[~2019-02-14 20:12 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-02-11 22:44 [PATCH 0/5] use pinned_vm instead of locked_vm to account pinned pages Daniel Jordan
2019-02-11 22:44 ` [PATCH 1/5] vfio/type1: " Daniel Jordan
2019-02-11 22:56 ` Jason Gunthorpe
2019-02-11 23:11 ` Daniel Jordan
2019-02-12 18:41 ` Alex Williamson
2019-02-13 0:26 ` Daniel Jordan
2019-02-13 20:03 ` Alex Williamson
2019-02-13 23:07 ` Jason Gunthorpe
2019-02-14 1:46 ` Daniel Jordan
2019-02-11 22:44 ` [PATCH 2/5] vfio/spapr_tce: " Daniel Jordan
2019-02-12 6:56 ` Alexey Kardashevskiy
2019-02-12 16:50 ` Christopher Lameter
2019-02-12 17:18 ` Daniel Jordan
2019-02-13 0:37 ` Alexey Kardashevskiy
2019-02-12 18:56 ` Alex Williamson
2019-02-13 0:34 ` Alexey Kardashevskiy
2019-02-11 22:44 ` [PATCH 3/5] fpga/dlf/afu: " Daniel Jordan
2019-02-11 22:44 ` [PATCH 4/5] powerpc/mmu: " Daniel Jordan
2019-02-13 1:14 ` kbuild test robot
2019-02-11 22:44 ` [PATCH 5/5] kvm/book3s: " Daniel Jordan
2019-02-13 1:43 ` kbuild test robot
2019-02-11 22:54 ` [PATCH 0/5] " Jason Gunthorpe
2019-02-11 23:15 ` Daniel Jordan
2019-02-14 1:53 ` Ira Weiny
2019-02-14 6:00 ` Jason Gunthorpe
2019-02-14 19:33 ` Ira Weiny
2019-02-14 20:12 ` Jason Gunthorpe [this message]
2019-02-14 21:46 ` Ira Weiny
2019-02-14 22:16 ` Jason Gunthorpe
2019-02-15 15:26 ` Christopher Lameter
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