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: <5574983a-3b32-f519-9012-a66b319fc6a8@redhat.com>
Date:   Tue, 2 May 2023 13:27:41 +0200
MIME-Version: 1.0
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101
 Thunderbird/102.10.0
Subject: Re: [PATCH 1/1] mm: change per-VMA lock statistics to be disabled by
 default
Content-Language: en-US
To:     Suren Baghdasaryan <surenb@google.com>, akpm@linux-foundation.org
Cc:     torvalds@linux-foundation.org, lstoakes@gmail.com, vbabka@suse.cz,
        linux-mm@kvack.org, linux-kernel@vger.kernel.org,
        kernel-team@android.com
References: <20230428173533.18158-1-surenb@google.com>
From:   David Hildenbrand <david@redhat.com>
Organization: Red Hat
In-Reply-To: <20230428173533.18158-1-surenb@google.com>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 7bit
Precedence: bulk

On 28.04.23 19:35, Suren Baghdasaryan wrote:
> Change CONFIG_PER_VMA_LOCK_STATS to be disabled by default, as most
> users don't need it. Add configuration help to clarify its usage.
> 
> Fixes: 52f238653e45 ("mm: introduce per-VMA lock statistics")
> Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
> Signed-off-by: Suren Baghdasaryan <surenb@google.com>
> ---
>   mm/Kconfig.debug | 10 ++++++++--
>   1 file changed, 8 insertions(+), 2 deletions(-)
> 
> diff --git a/mm/Kconfig.debug b/mm/Kconfig.debug
> index 6dae63b46368..a925415b4d10 100644
> --- a/mm/Kconfig.debug
> +++ b/mm/Kconfig.debug
> @@ -274,6 +274,12 @@ config DEBUG_KMEMLEAK_AUTO_SCAN
>   config PER_VMA_LOCK_STATS
>   	bool "Statistics for per-vma locks"
>   	depends on PER_VMA_LOCK
> -	default y
>   	help
> -	  Statistics for per-vma locks.
> +	  Say Y here to enable success, retry and failure counters of page
> +	  faults handled under protection of per-vma locks. When enabled, the
> +	  counters are exposed in /proc/vmstat. This information is useful for
> +	  kernel developers to evaluate effectiveness of per-vma locks and to
> +	  identify pathological cases. Counting these events introduces a small
> +	  overhead in the page fault path.
> +
> +	  If in doubt, say N.

Reviewed-by: David Hildenbrand <david@redhat.com>

-- 
Thanks,

David / dhildenb