linux-kernel - Re: [PATCH v4 03/10] mm: apply per-task gfp constraints in fast path

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Date:   Fri, 18 Dec 2020 10:36:53 +0100
From:   Michal Hocko <mhocko@...e.com>
To:     Pavel Tatashin <pasha.tatashin@...een.com>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        akpm@...ux-foundation.org, vbabka@...e.cz, david@...hat.com,
        osalvador@...e.de, dan.j.williams@...el.com, sashal@...nel.org,
        tyhicks@...ux.microsoft.com, iamjoonsoo.kim@....com,
        mike.kravetz@...cle.com, rostedt@...dmis.org, mingo@...hat.com,
        jgg@...pe.ca, peterz@...radead.org, mgorman@...e.de,
        willy@...radead.org, rientjes@...gle.com, jhubbard@...dia.com,
        linux-doc@...r.kernel.org, ira.weiny@...el.com,
        linux-kselftest@...r.kernel.org
Subject: Re: [PATCH v4 03/10] mm: apply per-task gfp constraints in fast path

On Thu 17-12-20 13:52:36, Pavel Tatashin wrote:
[..]
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 469016222cdb..d9546f5897f4 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -3234,11 +3234,12 @@ static bool throttle_direct_reclaim(gfp_t gfp_mask, struct zonelist *zonelist,
>  unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
>  				gfp_t gfp_mask, nodemask_t *nodemask)
>  {
> +	gfp_t current_gfp_mask = current_gfp_context(gfp_mask);
>  	unsigned long nr_reclaimed;
>  	struct scan_control sc = {
>  		.nr_to_reclaim = SWAP_CLUSTER_MAX,
> -		.gfp_mask = current_gfp_context(gfp_mask),
> -		.reclaim_idx = gfp_zone(gfp_mask),
> +		.gfp_mask = current_gfp_mask,
> +		.reclaim_idx = gfp_zone(current_gfp_mask),
>  		.order = order,
>  		.nodemask = nodemask,
>  		.priority = DEF_PRIORITY,
> @@ -4158,17 +4159,18 @@ static int __node_reclaim(struct pglist_data *pgdat, gfp_t gfp_mask, unsigned in
>  {
>  	/* Minimum pages needed in order to stay on node */
>  	const unsigned long nr_pages = 1 << order;
> +	gfp_t current_gfp_mask = current_gfp_context(gfp_mask);
>  	struct task_struct *p = current;
>  	unsigned int noreclaim_flag;
>  	struct scan_control sc = {
>  		.nr_to_reclaim = max(nr_pages, SWAP_CLUSTER_MAX),
> -		.gfp_mask = current_gfp_context(gfp_mask),
> +		.gfp_mask = current_gfp_mask,
>  		.order = order,
>  		.priority = NODE_RECLAIM_PRIORITY,
>  		.may_writepage = !!(node_reclaim_mode & RECLAIM_WRITE),
>  		.may_unmap = !!(node_reclaim_mode & RECLAIM_UNMAP),
>  		.may_swap = 1,
> -		.reclaim_idx = gfp_zone(gfp_mask),
> +		.reclaim_idx = gfp_zone(current_gfp_mask),
>  	};
>  
>  	trace_mm_vmscan_node_reclaim_begin(pgdat->node_id, order,

I was hoping we had agreed these are not necessary and they shouldn't be
touched in the patch.
-- 
Michal Hocko
SUSE Labs