linux-kernel - Re: [PATCH v7 3/3] mm/mempolicy: Support memory hotplug in weighted interleave

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Message-ID: <Z_U2km48N_i-6gPq@gourry-fedora-PF4VCD3F>
Date: Tue, 8 Apr 2025 10:45:38 -0400
From: Gregory Price <gourry@...rry.net>
To: Rakie Kim <rakie.kim@...com>
Cc: akpm@...ux-foundation.org, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, linux-cxl@...r.kernel.org,
	joshua.hahnjy@...il.com, dan.j.williams@...el.com,
	ying.huang@...ux.alibaba.com, david@...hat.com,
	Jonathan.Cameron@...wei.com, osalvador@...e.de,
	kernel_team@...ynix.com, honggyu.kim@...com, yunjeong.mun@...com
Subject: Re: [PATCH v7 3/3] mm/mempolicy: Support memory hotplug in weighted
 interleave

On Tue, Apr 08, 2025 at 04:32:42PM +0900, Rakie Kim wrote:
> The weighted interleave policy distributes page allocations across multiple
> NUMA nodes based on their performance weight, thereby improving memory
> bandwidth utilization. The weight values for each node are configured
> through sysfs.
> 
> Previously, sysfs entries for configuring weighted interleave were created
> for all possible nodes (N_POSSIBLE) at initialization, including nodes that
> might not have memory. However, not all nodes in N_POSSIBLE are usable at
> runtime, as some may remain memoryless or offline.
> This led to sysfs entries being created for unusable nodes, causing
> potential misconfiguration issues.
> 
> To address this issue, this patch modifies the sysfs creation logic to:
> 1) Limit sysfs entries to nodes that are online and have memory, avoiding
>    the creation of sysfs entries for nodes that cannot be used.
> 2) Support memory hotplug by dynamically adding and removing sysfs entries
>    based on whether a node transitions into or out of the N_MEMORY state.
> 
> Additionally, the patch ensures that sysfs attributes are properly managed
> when nodes go offline, preventing stale or redundant entries from persisting
> in the system.
> 
> By making these changes, the weighted interleave policy now manages its
> sysfs entries more efficiently, ensuring that only relevant nodes are
> considered for interleaving, and dynamically adapting to memory hotplug
> events.
> 
> Signed-off-by: Rakie Kim <rakie.kim@...com>
> Signed-off-by: Honggyu Kim <honggyu.kim@...com>
> Signed-off-by: Yunjeong Mun <yunjeong.mun@...com>
> Reviewed-by: Oscar Salvador <osalvador@...e.de>

Reviewed-by: Gregory Price <gourry@...rry.net>