linux-kernel - Re: [PATCH 1/3] IMA: move read/write counters into struct inode

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Date:	Wed, 20 Oct 2010 11:25:35 -0400
From:	Eric Paris <eparis@...hat.com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Al Viro <viro@...iv.linux.org.uk>,
	linux-kernel@...r.kernel.org,
	linux-security-module@...r.kernel.org,
	linux-fsdevel@...r.kernel.org, hch@...radead.org, zohar@...ibm.com,
	warthog9@...nel.org, david@...morbit.com, jmorris@...ei.org,
	kyle@...artin.ca, hpa@...or.com, akpm@...ux-foundation.org
Subject: Re: [PATCH 1/3] IMA: move read/write counters into struct inode

On Wed, 2010-10-20 at 17:15 +0200, Ingo Molnar wrote:
> * Eric Paris <eparis@...hat.com> wrote:
> 
> > On Wed, 2010-10-20 at 16:38 +0200, Ingo Molnar wrote:
> > > * Eric Paris <eparis@...hat.com> wrote:
> > > 
> > > > Executive summary of the day's work:
> > > > Yesterday morning: 944 bytes per inode in core
> > > > Yesterday night: 24 bytes per inode in core
> > > > Tonight: 4 bytes per inode in core.
> > > > 
> > > > That's a x236 time reduction in memory usage.  No I didn't even start looking 
> > > > at a freezer.  Which could bring that 4 down to 0, but would add a scalability 
> > > > penalty on all inodes when IMA was enabled.
> > > 
> > > Why not use inode->i_security intelligently? That already exists so that way 
> > > it's 0 bytes.
> > > 
> > > Thanks,
> > 
> > It still wouldn't be 0 bytes since there would be a 1-1 mapping from inode to 
> > i_security structs. [...]
> 
> Only for IMA-affected files, right?

No, we need to keep the open read counter even for non-IMA-affected
files in case we later determine that it is IMA-affected.  That's the 4
bytes I have today, which I said could be eliminated with a freezer that
calculated it when IMA was enabled, but isn't something I'm looking at
right now....

-Eric

-Eric

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