linux-kernel - Re: [RFC PATCH v3 5/7] mm/damon/paddr: introduce DAMOS_MIGRATE

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Date: Fri,  5 Apr 2024 16:55:57 +0900
From: Hyeongtak Ji <hyeongtak.ji@...il.com>
To: Honggyu Kim <honggyu.kim@...com>
Cc: akpm@...ux-foundation.org,
	apopple@...dia.com,
	baolin.wang@...ux.alibaba.com,
	dave.jiang@...el.com,
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	mathieu.desnoyers@...icios.com,
	mhiramat@...nel.org,
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	ying.huang@...el.com,
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	art.jeongseob@...il.com
Subject: Re: [RFC PATCH v3 5/7] mm/damon/paddr: introduce DAMOS_MIGRATE_COLD action for demotion

On Fri,  5 Apr 2024 15:08:54 +0900 Honggyu Kim <honggyu.kim@...com> wrote:

..snip...

> +static unsigned long damon_pa_migrate_pages(struct list_head *folio_list,
> +					    enum migration_mode mm,
> +					    int target_nid)
> +{
> +	int nid;
> +	unsigned int nr_migrated = 0;
> +	LIST_HEAD(node_folio_list);
> +	unsigned int noreclaim_flag;
> +
> +	if (list_empty(folio_list))
> +		return nr_migrated;

How about checking if `target_nid` is `NUMA_NO_NODE` or not earlier,

> +
> +	noreclaim_flag = memalloc_noreclaim_save();
> +
> +	nid = folio_nid(lru_to_folio(folio_list));
> +	do {
> +		struct folio *folio = lru_to_folio(folio_list);
> +
> +		if (nid == folio_nid(folio)) {
> +			folio_clear_active(folio);
> +			list_move(&folio->lru, &node_folio_list);
> +			continue;
> +		}
> +
> +		nr_migrated += damon_pa_migrate_folio_list(&node_folio_list,
> +							   NODE_DATA(nid), mm,
> +							   target_nid);
> +		nid = folio_nid(lru_to_folio(folio_list));
> +	} while (!list_empty(folio_list));
> +
> +	nr_migrated += damon_pa_migrate_folio_list(&node_folio_list,
> +						   NODE_DATA(nid), mm,
> +						   target_nid);
> +
> +	memalloc_noreclaim_restore(noreclaim_flag);
> +
> +	return nr_migrated;
> +}
> +

..snip...

> +static unsigned int migrate_folio_list(struct list_head *migrate_folios,
> +				       struct pglist_data *pgdat,
> +				       int target_nid)
> +{
> +	unsigned int nr_succeeded;
> +	nodemask_t allowed_mask = NODE_MASK_NONE;
> +
> +	struct migration_target_control mtc = {
> +		/*
> +		 * Allocate from 'node', or fail quickly and quietly.
> +		 * When this happens, 'page' will likely just be discarded
> +		 * instead of migrated.
> +		 */
> +		.gfp_mask = (GFP_HIGHUSER_MOVABLE & ~__GFP_RECLAIM) | __GFP_NOWARN |
> +			__GFP_NOMEMALLOC | GFP_NOWAIT,
> +		.nid = target_nid,
> +		.nmask = &allowed_mask
> +	};
> +
> +	if (pgdat->node_id == target_nid || target_nid == NUMA_NO_NODE)
> +		return 0;

instead of here.

> +
> +	if (list_empty(migrate_folios))
> +		return 0;
> +
> +	/* Migration ignores all cpuset and mempolicy settings */
> +	migrate_pages(migrate_folios, alloc_migrate_folio, NULL,
> +		      (unsigned long)&mtc, MIGRATE_ASYNC, MR_DAMON,
> +		      &nr_succeeded);
> +
> +	return nr_succeeded;
> +}
> +

..snip...

Kind regards,
Hyeongtak