linux-kernel - Re: [PATCH v2 00/15] slab: overload struct slab over struct page to reduce memory usage

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Message-ID: <8738nwvqah.fsf@tassilo.jf.intel.com>
Date:	Sat, 19 Oct 2013 15:39:34 -0700
From:	Andi Kleen <andi@...stfloor.org>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Joonsoo Kim <iamjoonsoo.kim@....com>,
	Pekka Enberg <penberg@...nel.org>,
	Christoph Lameter <cl@...ux.com>,
	Joonsoo Kim <js1304@...il.com>,
	David Rientjes <rientjes@...gle.com>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	Wanpeng Li <liwanp@...ux.vnet.ibm.com>
Subject: Re: [PATCH v2 00/15] slab: overload struct slab over struct page to reduce memory usage

Andrew Morton <akpm@...ux-foundation.org> writes:
>
> One example is mm/memory-failure.c:memory_failure().  It starts with a
> raw pfn, uses that to get at the `struct page', then starts playing
> around with it.  Will that code still work correctly when some of the
> page's fields have been overlayed with slab-specific contents?

As long as PageSlab() works correctly memory_failure should be happy.

>
> This issue hasn't been well thought through.  Given a random struct
> page, there isn't any protocol to determine what it actually *is*. 
> It's a plain old variant record, but it lacks the agreed-upon tag field
> which tells users which variant is currently in use.

PageSlab() should work for this right?

For the generic case it may not though.

-Andi

-- 
ak@...ux.intel.com -- Speaking for myself only
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