Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Message-ID: <efc76ea3-9a85-96a3-f3d7-212aeea7cf1c@suse.cz>
Date:   Tue, 30 May 2023 10:32:04 +0200
MIME-Version: 1.0
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101
 Thunderbird/102.11.2
Subject: Re: [PATCH 6/6] mm: compaction: skip fast freepages isolation if
 enough freepages are isolated
Content-Language: en-US
To:     Baolin Wang <baolin.wang@linux.alibaba.com>,
        akpm@linux-foundation.org
Cc:     mgorman@techsingularity.net, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org
References: <cover.1685018752.git.baolin.wang@linux.alibaba.com>
 <f39c2c07f2dba2732fd9c0843572e5bef96f7f67.1685018752.git.baolin.wang@linux.alibaba.com>
From:   Vlastimil Babka <vbabka@suse.cz>
In-Reply-To: <f39c2c07f2dba2732fd9c0843572e5bef96f7f67.1685018752.git.baolin.wang@linux.alibaba.com>
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 7bit
Precedence: bulk

On 5/25/23 14:54, Baolin Wang wrote:
> I've observed that fast isolation often isolates more pages than
> cc->migratepages, and the excess freepages will be released back to the
> buddy system. So skip fast freepages isolation if enough freepages are
> isolated to save some CPU cycles.
> 
> Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com>

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

> ---
>  mm/compaction.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/mm/compaction.c b/mm/compaction.c
> index eccec84dae82..3ade4c095ed2 100644
> --- a/mm/compaction.c
> +++ b/mm/compaction.c
> @@ -1550,6 +1550,10 @@ static void fast_isolate_freepages(struct compact_control *cc)
>  
>  		spin_unlock_irqrestore(&cc->zone->lock, flags);
>  
> +		/* Skip fast search if enough freepages isolated */
> +		if (cc->nr_freepages >= cc->nr_migratepages)
> +			break;
> +
>  		/*
>  		 * Smaller scan on next order so the total scan is related
>  		 * to freelist_scan_limit.