linux-ext4 - Re: [PATCH v3 0/2] ext4: increase mbcache scalability

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Date:	Thu, 3 Oct 2013 21:22:09 -0600
From:	Andreas Dilger <adilger@...ger.ca>
To:	Thavatchai Makphaibulchoke <thavatchai.makpahibulchoke@...com>
Cc:	Theodore Ts'o <tytso@....edu>, Eric Sandeen <sandeen@...hat.com>,
	"linux-ext4@...r.kernel.org List" <linux-ext4@...r.kernel.org>,
	aswin@...com
Subject: Re: [PATCH v3 0/2] ext4: increase mbcache scalability

On 2013-09-25, at 12:43 PM, Thavatchai Makphaibulchoke wrote:
> On 09/21/2013 05:12 PM, Andreas Dilger wrote:
>> I just noticed that we have a patch for Lustre that adds a "no_mbcache" mount option to disable mbcache on a per-filesystem basis.
>> 
>> The newest patch we have is based on FC19 (3.10 kernel), is this something that would be of interest if we submitted it upstream?
>> 
>> http://review.whamcloud.com/#/c/7263/8/ldiskfs/kernel_patches/patches/fc19/ext4-disable-mb-cache.patch
>> 
>> Cheers, Andreas
>> 
> 
> Here are some of the improvement I saw with SELinux disabled.

To confirm, is this data on your "128-byte inode on ramdisk" config,
or is this on a system with a real disk and 256-byte inodes?

> On an 80 core machine,
> 
> custom 15.5%
> disk 27.81
> fserver 5.33%
> new_dbase 9.06%
> new_fserver 5.45%
> 
> 
> On an 8 core machine,
> 
> alltests 5.24
> custom 2.26
> shared 9.32
> short 24.08
> 
> The rest is not noticably different.

This is a pretty significant price to pay for SELinux in any case.
I guess it is probably lower overhead with 256-byte inodes, but
anything that adds 5-25% overhead shouldn't be taken for granted.

Cheers, Andreas





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