linux-kernel - Re: [RFC PATCH v0 2/2] mm: sched: Batch-migrate misplaced pages

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Message-ID: <62cef618-123c-4ffa-b45a-c38b65d2a5a3@redhat.com>
Date: Thu, 22 May 2025 18:11:13 +0200
From: David Hildenbrand <david@...hat.com>
To: Bharata B Rao <bharata@....com>, linux-kernel@...r.kernel.org,
 linux-mm@...ck.org
Cc: Jonathan.Cameron@...wei.com, dave.hansen@...el.com, gourry@...rry.net,
 hannes@...xchg.org, mgorman@...hsingularity.net, mingo@...hat.com,
 peterz@...radead.org, raghavendra.kt@....com, riel@...riel.com,
 rientjes@...gle.com, sj@...nel.org, weixugc@...gle.com, willy@...radead.org,
 ying.huang@...ux.alibaba.com, ziy@...dia.com, dave@...olabs.net,
 nifan.cxl@...il.com, joshua.hahnjy@...il.com, xuezhengchu@...wei.com,
 yiannis@...corp.com, akpm@...ux-foundation.org
Subject: Re: [RFC PATCH v0 2/2] mm: sched: Batch-migrate misplaced pages

On 21.05.25 10:02, Bharata B Rao wrote:
> Currently the folios identified as misplaced by the NUMA
> balancing sub-system are migrated one by one from the NUMA
> hint fault handler as and when they are identified as
> misplaced.
> 
> Instead of such singe folio migrations, batch them and
> migrate them at once.
> 
> Identified misplaced folios are isolated and stored in
> a per-task list. A new task_work is queued from task tick
> handler to migrate them in batches. Migration is done
> periodically or if pending number of isolated foios exceeds
> a threshold.

That means that these pages are effectively unmovable for other purposes 
(CMA, compaction, long-term pinning, whatever) until that list was drained.

Bad.

-- 
Cheers,

David / dhildenb