From: Andrew Morton <akpm@linux-foundation.org>
To: "Huang, Ying" <ying.huang@intel.com>
Cc: Donet Tom <donettom@linux.ibm.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
Aneesh Kumar <aneesh.kumar@kernel.org>,
Michal Hocko <mhocko@kernel.org>,
Dave Hansen <dave.hansen@linux.intel.com>,
Mel Gorman <mgorman@suse.de>, Feng Tang <feng.tang@intel.com>,
Andrea Arcangeli <aarcange@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@redhat.com>, Rik van Riel <riel@surriel.com>,
Johannes Weiner <hannes@cmpxchg.org>,
Matthew Wilcox <willy@infradead.org>,
Vlastimil Babka <vbabka@suse.cz>,
Dan Williams <dan.j.williams@intel.com>,
Hugh Dickins <hughd@google.com>,
Kefeng Wang <wangkefeng.wang@huawei.com>,
Suren Baghdasaryan <surenb@google.com>
Subject: Re: [PATCH v2 2/2] mm/numa_balancing:Allow migrate on protnone reference with MPOL_PREFERRED_MANY policy
Date: Wed, 13 Mar 2024 08:51:44 -0700 [thread overview]
Message-ID: <20240313085144.13b37a79c688b6126af0bd07@linux-foundation.org> (raw)
In-Reply-To: <874jdd5z1b.fsf@yhuang6-desk2.ccr.corp.intel.com>
On Mon, 11 Mar 2024 09:37:36 +0800 "Huang, Ying" <ying.huang@intel.com> wrote:
> > @@ -2515,15 +2516,26 @@ int mpol_misplaced(struct folio *folio, struct vm_fault *vmf,
> > break;
> >
> > case MPOL_BIND:
> > - /* Optimize placement among multiple nodes via NUMA balancing */
> > + case MPOL_PREFERRED_MANY:
> > + /*
> > + * Even though MPOL_PREFERRED_MANY can allocate pages outside
> > + * policy nodemask we don't allow numa migration to nodes
> > + * outside policy nodemask for now. This is done so that if we
> > + * want demotion to slow memory to happen, before allocating
> > + * from some DRAM node say 'x', we will end up using a
> > + * MPOL_PREFERRED_MANY mask excluding node 'x'. In such scenario
> > + * we should not promote to node 'x' from slow memory node.
> > + */
>
> This is a little hard to digest for me. And, I don't think that we need
> to put this policy choice in code comments. It's better to put it in
> patch description. Where we can give more background, for example, to
> avoid cross-socket traffic, etc.
Oh. I like the comment. We could perhaps put additional detail in the
changelog, but using changelogs to understand the code is so darned
inconvenient.
next prev parent reply other threads:[~2024-03-13 15:51 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-03-08 15:15 [PATCH v2 0/2] Allow migrate on protnone reference with MPOL_PREFERRED_MANY policy Donet Tom
2024-03-08 15:15 ` [PATCH v2 2/2] mm/numa_balancing:Allow " Donet Tom
2024-03-11 1:37 ` Huang, Ying
2024-03-13 15:51 ` Andrew Morton [this message]
2024-03-11 1:45 ` [PATCH v2 0/2] Allow " Huang, Ying
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