linux-kernel - Re: [PATCH] audit: remove the audit freelist

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Message-ID: <20161201014455.GD26507@breakpoint.cc>
Date:   Thu, 1 Dec 2016 02:44:55 +0100
From:   Florian Westphal <fw@...len.de>
To:     Paul Moore <paul@...l-moore.com>
Cc:     Florian Westphal <fw@...len.de>, linux-kernel@...r.kernel.org,
        linux-audit@...hat.com, Eric Paris <eparis@...hat.com>
Subject: Re: [PATCH] audit: remove the audit freelist

Paul Moore <paul@...l-moore.com> wrote:
> On Tue, Nov 15, 2016 at 8:16 AM, Florian Westphal <fw@...len.de> wrote:
> > allows better debugging as freeing audit buffers now always honors slub
> > debug hooks (e.g. object poisoning) and leak checker can detect the
> > free operation.
> >
> > Removal also results in a small speedup (using
> > single rule 'iptables -A INPUT -i lo -j AUDIT --type drop'):
> >
> > super_netperf 4 -H 127.0.0.1 -l 360 -t UDP_RR -- -R 1 -m 64
> > Before:
> > 294953
> > After:
> > 298013
> >
> > (alloc/free no longer serializes on spinlock, allocator can use percpu
> >  pool).
> >
> > Signed-off-by: Florian Westphal <fw@...len.de>
> > ---
> >  kernel/audit.c | 53 ++++++++---------------------------------------------
> >  1 file changed, 8 insertions(+), 45 deletions(-)
> 
> Sorry for the delay, I was hoping to have some time to play around
> with this and offer a more meaningful comment ... I've often wondered
> about converting audit_buffer, and audit_context for that matter, over
> to their own kmem_cache; have you considered that?  Or was this
> proposed due to simplicity?

Not sure I understand, you could still convert it on top of this.
(Although audit_buffer is just 24 bytes after this patch so it will
 come from 32byte kmalloc slab).

I don't think it makes sense to keep this DIY cache on top of slub
cache.