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Message-ID: <f28a74c8-69c5-fd65-778f-48e68aed99df@suse.cz>
Date:   Thu, 14 Oct 2021 17:41:17 +0200
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Subject: Re: [PATCH 8/8] mm/vmscan: Delay waking of tasks throttled on
 NOPROGRESS
Content-Language: en-US
To:     Mel Gorman <mgorman@techsingularity.net>,
        Linux-MM <linux-mm@kvack.org>
Cc:     NeilBrown <neilb@suse.de>, Theodore Ts'o <tytso@mit.edu>,
        Andreas Dilger <adilger.kernel@dilger.ca>,
        "Darrick J . Wong" <djwong@kernel.org>,
        Matthew Wilcox <willy@infradead.org>,
        Michal Hocko <mhocko@suse.com>,
        Dave Chinner <david@fromorbit.com>,
        Rik van Riel <riel@surriel.com>,
        Johannes Weiner <hannes@cmpxchg.org>,
        Jonathan Corbet <corbet@lwn.net>,
        Linux-fsdevel <linux-fsdevel@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>
References: <20211008135332.19567-1-mgorman@techsingularity.net>
 <20211008135332.19567-9-mgorman@techsingularity.net>
From:   Vlastimil Babka <vbabka@suse.cz>
In-Reply-To: <20211008135332.19567-9-mgorman@techsingularity.net>
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On 10/8/21 15:53, Mel Gorman wrote:
> Tracing indicates that tasks throttled on NOPROGRESS are woken
> prematurely resulting in occasional massive spikes in direct
> reclaim activity. This patch wakes tasks throttled on NOPROGRESS
> if reclaim efficiency is at least 12%.
> 
> Signed-off-by: Mel Gorman <mgorman@techsingularity.net>

Acked-by: Vlastimil Babka <vbabka@suse.cz>

> ---
>  mm/vmscan.c | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 7b54fec4072c..80a9a26f701f 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -3338,8 +3338,11 @@ static inline bool compaction_ready(struct zone *zone, struct scan_control *sc)
>  
>  static void consider_reclaim_throttle(pg_data_t *pgdat, struct scan_control *sc)
>  {
> -	/* If reclaim is making progress, wake any throttled tasks. */
> -	if (sc->nr_reclaimed) {
> +	/*
> +	 * If reclaim is making progress greater than 12% efficiency then
> +	 * wake all the NOPROGRESS throttled tasks.
> +	 */
> +	if (sc->nr_reclaimed > (sc->nr_scanned >> 3)) {
>  		wait_queue_head_t *wqh;
>  
>  		wqh = &pgdat->reclaim_wait[VMSCAN_THROTTLE_NOPROGRESS];
>