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Message-ID: <aF4etw9dELyW7FEZ@gourry-fedora-PF4VCD3F>
Date: Fri, 27 Jun 2025 00:31:51 -0400
From: Gregory Price <gourry@...rry.net>
To: Joshua Hahn <joshua.hahnjy@...il.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
Alistair Popple <apopple@...dia.com>,
Byungchul Park <byungchul@...com>,
David Hildenbrand <david@...hat.com>,
Matthew Brost <matthew.brost@...el.com>,
Rakie Kim <rakie.kim@...com>,
Ying Huang <ying.huang@...ux.alibaba.com>, Zi Yan <ziy@...dia.com>,
linux-kernel@...r.kernel.org, linux-mm@...ck.org,
kernel-team@...a.com
Subject: Re: [PATCH 1/2] mm/mempolicy: Simplify weighted interleave bulk
alloc calculations
On Thu, Jun 26, 2025 at 01:09:33PM -0700, Joshua Hahn wrote:
> Simplify the math used to figure out how many pages should be allocated
> per node. Instead of making conditional additions and deletions, we can just
> make them unconditional by using min(). No functional changes intended.
>
> Signed-off-by: Joshua Hahn <joshua.hahnjy@...il.com>
you're better at concise math than I am :]
Reviewed-by: Gregory Price <gourry@...rry.net>
>
> ---
> mm/mempolicy.c | 15 ++++++---------
> 1 file changed, 6 insertions(+), 9 deletions(-)
>
> diff --git a/mm/mempolicy.c b/mm/mempolicy.c
> index 3b1dfd08338b..78ad74a0e249 100644
> --- a/mm/mempolicy.c
> +++ b/mm/mempolicy.c
> @@ -2645,18 +2645,15 @@ static unsigned long alloc_pages_bulk_weighted_interleave(gfp_t gfp,
> for (i = 0; i < nnodes; i++) {
> node = next_node_in(prev_node, nodes);
> weight = weights[node];
> - node_pages = weight * rounds;
> - /* If a delta exists, add this node's portion of the delta */
> - if (delta > weight) {
> - node_pages += weight;
> - delta -= weight;
> - } else if (delta) {
> - /* when delta is depleted, resume from that node */
> - node_pages += delta;
> + /* when delta is depleted, resume from that node */
> + if (delta && delta < weight) {
> resume_node = node;
> resume_weight = weight - delta;
> - delta = 0;
> }
> + /* Add the node's portion of the delta, if there is one */
> + node_pages = weight * rounds + min(delta, weight);
> + delta -= min(delta, weight);
> +
> /* node_pages can be 0 if an allocation fails and rounds == 0 */
> if (!node_pages)
> break;
> --
> 2.47.1
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