linux-kernel - Re: ext4 extent status tree LRU locking

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Message-ID: <51BB3D78.2070907@intel.com>
Date:	Fri, 14 Jun 2013 08:57:44 -0700
From:	Dave Hansen <dave.hansen@...el.com>
To:	linux-ext4@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
	Theodore Ts'o <tytso@....edu>, Jan kara <jack@...e.cz>
Subject: Re: ext4 extent status tree LRU locking

On 06/14/2013 07:09 AM, Zheng Liu wrote:
> -	INIT_LIST_HEAD(&scanned);
> -
>  	spin_lock(&sbi->s_es_lru_lock);
> +	list_sort(NULL, &sbi->s_es_lru, ext4_inode_touch_time_cmp);
>  	list_for_each_safe(cur, tmp, &sbi->s_es_lru) {

How long can this list get?  I have the feeling this might get a bit
painful, especially on a NUMA machine.

But, it definitely eliminates the spinlock contention that I was seeing.
 The top ext4 function in my profiles is way down under 1% of CPU time
now.  Thanks for the quick response, and please let me know if you need
any further testing.
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