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Date: Tue, 26 Jan 2016 09:48:29 +0100
From: Paul Bolle <pebolle@...cali.nl>
To: Laura Abbott <labbott@...oraproject.org>
Cc: Christoph Lameter <cl@...ux.com>, Pekka Enberg <penberg@...nel.org>,
David Rientjes <rientjes@...gle.com>, Joonsoo Kim <js1304@...il.com>,
Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
linux-kernel@...r.kernel.org, kernel-hardening@...ts.openwall.com, Kees
Cook <keescook@...omium.org>
Subject: Re: [RFC][PATCH 2/3] slub: Don't limit debugging to slow paths
On ma, 2016-01-25 at 17:15 -0800, Laura Abbott wrote:
> --- a/init/Kconfig
> +++ b/init/Kconfig
> +config SLUB_DEBUG_FASTPATH
> + bool "Allow SLUB debugging to utilize the fastpath"
> + depends on SLUB_DEBUG
> + help
> + SLUB_DEBUG forces all allocations to utilize the slow path which
> + is a performance penalty. Turning on this option lets the debugging
> + use the fast path. This helps the performance when debugging
> + features are turned on. If you aren't planning on utilizing any
> + of the SLUB_DEBUG features, you should say N here.
> +
> + If unsure, say N
> --- a/mm/slub.c
> +++ b/mm/slub.c
> +#ifdef SLUB_DEBUG_FASTPATH
I have no clue what your patch does, but I could spot this should
probably be
#ifdef CONFIG_SLUB_DEBUG_FASTPATH
> +static noinline int alloc_debug_processing_fastpath(struct kmem_cache
> *s,
> + struct kmem_cache_cpu *c,
> + struct page *page,
> + void *object, unsigned long
> tid,
> + unsigned long addr)
> +{
> + unsigned long flags;
> + int ret = 0;
> +
> + preempt_disable();
> + local_irq_save(flags);
> +
> + /*
> + * We've now disabled preemption and IRQs but we still need
> + * to check that this is the right CPU
> + */
> + if (!this_cpu_cmpxchg_double(s->cpu_slab->freelist, s
> ->cpu_slab->tid,
> + c->freelist, tid,
> + c->freelist, tid))
> + goto out;
> +
> + ret = alloc_debug_processing(s, page, object, addr);
> +
> +out:
> + local_irq_restore(flags);
> + preempt_enable();
> + return ret;
> +}
> +#else
> +static noinline int alloc_debug_processing_fastpath(struct kmem_cache
> *s,
> + struct kmem_cache_cpu *c,
> + struct page *page,
> + void *object, unsigned long
> tid,
> + unsigned long addr)
> +{
> + return 1;
> +}
> +#endif
Thanks,
Paul Bolle
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