Re: [PATCH 3/3] mm: adjust vm_committed_as_batch according to vm overcommit policy

From: Matthew Wilcox <willy@infradead.org>
To: Feng Tang <feng.tang@intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	Michal Hocko <mhocko@suse.com>,
	Johannes Weiner <hannes@cmpxchg.org>,
	Mel Gorman <mgorman@suse.de>, Kees Cook <keescook@chromium.org>,
	Luis Chamberlain <mcgrof@kernel.org>,
	Iurii Zaikin <yzaikin@google.com>,
	andi.kleen@intel.com, tim.c.chen@intel.com,
	dave.hansen@intel.com, ying.huang@intel.com, linux-mm@kvack.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH 3/3] mm: adjust vm_committed_as_batch according to vm overcommit policy
Date: Fri, 8 May 2020 04:24:48 -0700	[thread overview]
Message-ID: <20200508112448.GP16070@bombadil.infradead.org> (raw)
In-Reply-To: <1588922717-63697-4-git-send-email-feng.tang@intel.com>

On Fri, May 08, 2020 at 03:25:17PM +0800, Feng Tang wrote:
> +void mm_compute_batch(void)
>  {
>  	u64 memsized_batch;
>  	s32 nr = num_present_cpus();
>  	s32 batch = max_t(s32, nr*2, 32);
> -
> -	/* batch size set to 0.4% of (total memory/#cpus), or max int32 */
> -	memsized_batch = min_t(u64, (totalram_pages()/nr)/256, 0x7fffffff);
> +	unsigned long ram_pages = totalram_pages();
> +
> +	/*
> +	 * For policy of OVERCOMMIT_NEVER, set batch size to 0.4%
> +	 * of (total memory/#cpus), and lift it to 6.25% for other
> +	 * policies to easy the possible lock contention for percpu_counter
> +	 * vm_committed_as, while the max limit is INT_MAX
> +	 */
> +	if (sysctl_overcommit_memory == OVERCOMMIT_NEVER)
> +		memsized_batch = min_t(u64, ram_pages/nr/256, INT_MAX);
> +	else
> +		memsized_batch = min_t(u64, ram_pages/nr/16, INT_MAX);
>  
>  	vm_committed_as_batch = max_t(s32, memsized_batch, batch);
> +	printk("vm_committed_as_batch = %d\n", vm_committed_as_batch);
>  }

You left a debugging printk in ...