From: Gregory Price <gregory.price@memverge.com>
To: "Huang, Ying" <ying.huang@intel.com>
Cc: Gregory Price <gourry.memverge@gmail.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
linux-doc@vger.kernel.org, linux-fsdevel@vger.kernel.org,
linux-api@vger.kernel.org, corbet@lwn.net,
akpm@linux-foundation.org, honggyu.kim@sk.com, rakie.kim@sk.com,
hyeongtak.ji@sk.com, mhocko@kernel.org, vtavarespetr@micron.com,
jgroves@micron.com, ravis.opensrc@micron.com,
sthanneeru@micron.com, emirakhur@micron.com, Hasan.Maruf@amd.com,
seungjun.ha@samsung.com, hannes@cmpxchg.org,
dan.j.williams@intel.com,
Srinivasulu Thanneeru <sthanneeru.opensrc@micron.com>
Subject: Re: [PATCH v2 3/3] mm/mempolicy: introduce MPOL_WEIGHTED_INTERLEAVE for weighted interleaving
Date: Tue, 23 Jan 2024 16:27:35 -0500 [thread overview]
Message-ID: <ZbAvR+U+tyLvsh8R@memverge.com> (raw)
In-Reply-To: <87a5owv454.fsf@yhuang6-desk2.ccr.corp.intel.com>
On Tue, Jan 23, 2024 at 04:35:19PM +0800, Huang, Ying wrote:
> Gregory Price <gregory.price@memverge.com> writes:
>
> > On Mon, Jan 22, 2024 at 11:54:34PM -0500, Gregory Price wrote:
> >> >
> >> > Can the above code be simplified as something like below?
> >> >
> >> > resume_node = prev_node;
> > --- resume_weight = 0;
> > +++ resume_weight = weights[node];
> >> > for (...) {
> >> > ...
> >> > }
> >> >
> >>
> >> I'll take another look at it, but this logic is annoying because of the
> >> corner case: me->il_prev can be NUMA_NO_NODE or an actual numa node.
> >>
> >
> > After a quick look, as long as no one objects to (me->il_prev) remaining
> > NUMA_NO_NODE
>
> MAX_NUMNODES-1 ?
>
When setting a new policy, the il_prev gets set to NUMA_NO_NODE. It's
not harmful and is just (-1), which is functionally the same as
(MAX_NUMNODES-1) for the purpose of iterating the nodemask with
next_node_in(). So it's fine to set (resume_node = me->il_prev)
as discussed.
I have a cleaned up function I'll push when i fix up a few other spots.
> > while having a weight assigned to pol->wil.cur_weight,
>
> I think that it is OK.
>
> And, IIUC, pol->wil.cur_weight can be 0, as in
> weighted_interleave_nodes(), if it's 0, it will be assigned to default
> weight for the node.
>
cur_weight is different than the global weights. cur_weight tells us
how many pages are remaining to allocate for the current node.
(cur_weight = 0) can happen in two scenarios:
- initial setting of mempolicy (NUMA_NO_NODE w/ cur_weight=0)
- weighted_interleave_nodes decrements it down to 0
Now that i'm looking at it - the second condition should not exist, and
we can eliminate it. The logic in weighted_interleave_nodes is actually
annoyingly unclear at the moment, so I'm going to re-factor it a bit to
be more explicit.
~Gregory
next prev parent reply other threads:[~2024-01-23 21:27 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-01-19 17:57 [PATCH v2 0/3] mm/mempolicy: weighted interleave mempolicy and sysfs extension Gregory Price
2024-01-19 17:57 ` [PATCH v2 1/3] mm/mempolicy: implement the sysfs-based weighted_interleave interface Gregory Price
2024-01-22 8:03 ` Huang, Ying
2024-01-22 16:58 ` Gregory Price
2024-01-19 17:57 ` [PATCH v2 2/3] mm/mempolicy: refactor a read-once mechanism into a function for re-use Gregory Price
2024-01-19 17:57 ` [PATCH v2 3/3] mm/mempolicy: introduce MPOL_WEIGHTED_INTERLEAVE for weighted interleaving Gregory Price
2024-01-23 3:02 ` Huang, Ying
2024-01-23 4:54 ` Gregory Price
2024-01-23 5:16 ` Gregory Price
2024-01-23 8:35 ` Huang, Ying
2024-01-23 21:27 ` Gregory Price [this message]
2024-01-24 1:51 ` Huang, Ying
2024-01-24 18:01 ` Gregory Price
2024-01-23 8:13 ` Huang, Ying
2024-01-23 8:40 ` Huang, Ying
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