linux-ext4 - Re: [PATCH] fix return value for mb_cache_shrink_fn when nr_to

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Date:	Tue, 20 Jul 2010 09:02:57 +0800
From:	shenghui <crosslonelyover@...il.com>
To:	Andreas Gruenbacher <agruen@...e.de>
Cc:	Christoph Hellwig <hch@...radead.org>,
	Eric Sandeen <sandeen@...hat.com>,
	linux-fsdevel@...r.kernel.org, viro@...iv.linux.org.uk,
	linux-mm@...ck.org, linux-ext4 <linux-ext4@...r.kernel.org>,
	kernel-janitors <kernel-janitors@...r.kernel.org>
Subject: Re: [PATCH] fix return value for mb_cache_shrink_fn when nr_to_scan > 
	0

2010/7/20 Andreas Gruenbacher <agruen@...e.de>:
> On Sunday 18 July 2010 08:36:59 Wang Sheng-Hui wrote:
>> I regenerated the patch. Please check it.
>
> The logic for calculating how many objects to free is still wrong:
> mb_cache_shrink_fn returns the number of entries scaled by
> sysctl_vfs_cache_pressure / 100.  It should also scale nr_to_scan by the
> inverse of that.  The sysctl_vfs_cache_pressure == 0 case (never scale) may
> require special attention.
>
> See dcache_shrinker() in fs/dcache.c.
>
> Thanks,
> Andreas
>

Sorry, I haven't found any special attention on
sysctl_vfs_cache_pressure == 0 case or scale
nr_to_scan in fs/dcache.c

 900static int shrink_dcache_memory(int nr, gfp_t gfp_mask)
 901{
 902        if (nr) {
 903                if (!(gfp_mask & __GFP_FS))
 904                        return -1;
 905                prune_dcache(nr);
 906        }
 907        return (dentry_stat.nr_unused / 100) * sysctl_vfs_cache_pressure;
 908}




-- 


Thanks and Best Regards,
shenghui
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