From: Michal Hocko <mhocko@kernel.org>
To: Ben Widawsky <ben.widawsky@intel.com>
Cc: linux-mm <linux-mm@kvack.org>, Andi Kleen <ak@linux.intel.com>,
Andrew Morton <akpm@linux-foundation.org>,
Christoph Lameter <cl@linux.com>,
Dan Williams <dan.j.williams@intel.com>,
Dave Hansen <dave.hansen@linux.intel.com>,
David Hildenbrand <david@redhat.com>,
David Rientjes <rientjes@google.com>,
Jason Gunthorpe <jgg@ziepe.ca>,
Johannes Weiner <hannes@cmpxchg.org>,
Jonathan Corbet <corbet@lwn.net>,
Kuppuswamy Sathyanarayanan
<sathyanarayanan.kuppuswamy@linux.intel.com>,
Lee Schermerhorn <lee.schermerhorn@hp.com>,
Li Xinhai <lixinhai.lxh@gmail.com>,
Mel Gorman <mgorman@techsingularity.net>,
Mike Kravetz <mike.kravetz@oracle.com>,
Mina Almasry <almasrymina@google.com>, Tejun Heo <tj@kernel.org>,
Vlastimil Babka <vbabka@suse.cz>,
linux-api@vger.kernel.org
Subject: Re: [PATCH 00/18] multiple preferred nodes
Date: Wed, 24 Jun 2020 20:39:17 +0200 [thread overview]
Message-ID: <20200624183917.GW1320@dhcp22.suse.cz> (raw)
In-Reply-To: <20200624161643.75fkkvsxlmp3bf2e@intel.com>
On Wed 24-06-20 09:16:43, Ben Widawsky wrote:
> On 20-06-24 09:52:16, Michal Hocko wrote:
> > On Tue 23-06-20 09:12:11, Ben Widawsky wrote:
> > > On 20-06-23 13:20:48, Michal Hocko wrote:
> > [...]
> > > > It would be also great to provide a high level semantic description
> > > > here. I have very quickly glanced through patches and they are not
> > > > really trivial to follow with many incremental steps so the higher level
> > > > intention is lost easily.
> > > >
> > > > Do I get it right that the default semantic is essentially
> > > > - allocate page from the given nodemask (with __GFP_RETRY_MAYFAIL
> > > > semantic)
> > > > - fallback to numa unrestricted allocation with the default
> > > > numa policy on the failure
> > > >
> > > > Or are there any usecases to modify how hard to keep the preference over
> > > > the fallback?
> > >
> > > tl;dr is: yes, and no usecases.
> >
> > OK, then I am wondering why the change has to be so involved. Except for
> > syscall plumbing the only real change to the allocator path would be
> > something like
> >
> > static nodemask_t *policy_nodemask(gfp_t gfp, struct mempolicy *policy)
> > {
> > /* Lower zones don't get a nodemask applied for MPOL_BIND */
> > if (unlikely(policy->mode == MPOL_BIND ||
> > policy->mode == MPOL_PREFERED_MANY) &&
> > apply_policy_zone(policy, gfp_zone(gfp)) &&
> > cpuset_nodemask_valid_mems_allowed(&policy->v.nodes))
> > return &policy->v.nodes;
> >
> > return NULL;
> > }
> >
> > alloc_pages_current
> >
> > if (pol->mode == MPOL_INTERLEAVE)
> > page = alloc_page_interleave(gfp, order, interleave_nodes(pol));
> > else {
> > gfp_t gfp_attempt = gfp;
> >
> > /*
> > * Make sure the first allocation attempt will try hard
> > * but eventually fail without OOM killer or other
> > * disruption before falling back to the full nodemask
> > */
> > if (pol->mode == MPOL_PREFERED_MANY)
> > gfp_attempt |= __GFP_RETRY_MAYFAIL;
> >
> > page = __alloc_pages_nodemask(gfp_attempt, order,
> > policy_node(gfp, pol, numa_node_id()),
> > policy_nodemask(gfp, pol));
> > if (!page && pol->mode == MPOL_PREFERED_MANY)
> > page = __alloc_pages_nodemask(gfp, order,
> > numa_node_id(), NULL);
> > }
> >
> > return page;
> >
> > similar (well slightly more hairy) in alloc_pages_vma
> >
> > Or do I miss something that really requires more involved approach like
> > building custom zonelists and other larger changes to the allocator?
>
> I think I'm missing how this allows selecting from multiple preferred nodes. In
> this case when you try to get the page from the freelist, you'll get the
> zonelist of the preferred node, and when you actually scan through on page
> allocation, you have no way to filter out the non-preferred nodes. I think the
> plumbing of multiple nodes has to go all the way through
> __alloc_pages_nodemask(). But it's possible I've missed the point.
policy_nodemask() will provide the nodemask which will be used as a
filter on the policy_node.
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2020-06-24 18:39 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-19 16:24 [PATCH 00/18] multiple preferred nodes Ben Widawsky
2020-06-19 16:24 ` [PATCH 01/18] mm/mempolicy: Add comment for missing LOCAL Ben Widawsky
2020-06-24 7:55 ` Michal Hocko
2020-06-19 16:24 ` [PATCH 02/18] mm/mempolicy: Use node_mem_id() instead of node_id() Ben Widawsky
2020-06-24 8:25 ` Michal Hocko
2020-06-24 16:48 ` Ben Widawsky
2020-06-26 12:30 ` Michal Hocko
2020-06-19 16:24 ` [PATCH 03/18] mm/page_alloc: start plumbing multi preferred node Ben Widawsky
2020-06-19 16:24 ` [PATCH 04/18] mm/page_alloc: add preferred pass to page allocation Ben Widawsky
2020-06-19 16:24 ` [PATCH 05/18] mm/mempolicy: convert single preferred_node to full nodemask Ben Widawsky
2020-06-19 16:24 ` [PATCH 06/18] mm/mempolicy: Add MPOL_PREFERRED_MANY for multiple preferred nodes Ben Widawsky
2020-06-19 16:24 ` [PATCH 07/18] mm/mempolicy: allow preferred code to take a nodemask Ben Widawsky
2020-06-19 16:24 ` [PATCH 08/18] mm/mempolicy: refactor rebind code for PREFERRED_MANY Ben Widawsky
2020-06-19 16:24 ` [PATCH 09/18] mm: Finish handling MPOL_PREFERRED_MANY Ben Widawsky
2020-06-19 16:24 ` [PATCH 10/18] mm: clean up alloc_pages_vma (thp) Ben Widawsky
2020-06-19 16:24 ` [PATCH 11/18] mm: Extract THP hugepage allocation Ben Widawsky
2020-06-19 16:24 ` [PATCH 12/18] mm/mempolicy: Use __alloc_page_node for interleaved Ben Widawsky
2020-06-19 16:24 ` [PATCH 13/18] mm: kill __alloc_pages Ben Widawsky
2020-06-19 16:24 ` [PATCH 14/18] mm/mempolicy: Introduce policy_preferred_nodes() Ben Widawsky
2020-06-19 16:24 ` [PATCH 15/18] mm: convert callers of __alloc_pages_nodemask to pmask Ben Widawsky
2020-06-19 16:24 ` [PATCH 16/18] alloc_pages_nodemask: turn preferred nid into a nodemask Ben Widawsky
2020-06-19 16:24 ` [PATCH 17/18] mm: Use less stack for page allocations Ben Widawsky
2020-06-19 16:24 ` [PATCH 18/18] mm/mempolicy: Advertise new MPOL_PREFERRED_MANY Ben Widawsky
2020-06-22 7:09 ` [PATCH 00/18] multiple preferred nodes Michal Hocko
2020-06-23 11:20 ` Michal Hocko
2020-06-23 16:12 ` Ben Widawsky
2020-06-24 7:52 ` Michal Hocko
2020-06-24 16:16 ` Ben Widawsky
2020-06-24 18:39 ` Michal Hocko [this message]
2020-06-24 19:37 ` Ben Widawsky
2020-06-24 19:51 ` Michal Hocko
2020-06-24 20:01 ` Ben Widawsky
2020-06-24 20:07 ` Michal Hocko
2020-06-24 20:23 ` Ben Widawsky
2020-06-24 20:42 ` Michal Hocko
2020-06-24 20:55 ` Ben Widawsky
2020-06-25 6:28 ` Michal Hocko
2020-06-26 21:39 ` Ben Widawsky
2020-06-29 10:16 ` Michal Hocko
2020-06-22 20:54 ` Andi Kleen
2020-06-22 21:02 ` Ben Widawsky
2020-06-22 21:07 ` Dave Hansen
2020-06-22 22:02 ` Andi Kleen
-- strict thread matches above, loose matches on Subject: below --
2020-06-19 16:23 Ben Widawsky
2020-06-19 16:25 ` Ben Widawsky
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