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

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Date:	Wed, 11 Sep 2013 13:32:26 -0700 (PDT)
From:	David Lang <david@...g.hm>
To:	Eric Sandeen <sandeen@...hat.com>
cc:	"Theodore Ts'o" <tytso@....edu>,
	Andreas Dilger <adilger@...ger.ca>,
	Thavatchai Makphaibulchoke <thavatchai.makpahibulchoke@...com>,
	T Makphaibulchoke <tmac@...com>,
	Al Viro <viro@...iv.linux.org.uk>,
	"linux-ext4@...r.kernel.org List" <linux-ext4@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	"linux-fsdevel@...r.kernel.org Devel" <linux-fsdevel@...r.kernel.org>,
	aswin@...com, Linus Torvalds <torvalds@...ux-foundation.org>,
	aswin_proj@...ts.hp.com
Subject: Re: [PATCH v3 0/2] ext4: increase mbcache scalability

On Wed, 11 Sep 2013, Eric Sandeen wrote:

>> The reason why I'm pushing here is that mbcache shouldn't be showing
>> up in the profiles at all if there is no external xattr block.  And so
>> if newer versions of SELinux (like Adnreas, I've been burned by
>> SELinux too many times in the past, so I don't use SELinux on any of
>> my systems) is somehow causing mbcache to get triggered, we should
>> figure this out and understand what's really going on.
>
> selinux, from an fs allocation behavior perspective, is simply setxattr.

what you are missing is that Ted is saying that unless you are using xattrs, the 
mbcache should not show up at all.

The fact that you are using SElinux, and SELinux sets the xattrs is what makes 
this show up on your system, but other people who don't use SELinux (and so 
don't have any xattrs set) don't see the same bottleneck.

David Lang
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