From: Dave Hansen <dave@linux.vnet.ibm.com>
To: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Brian King <brking@linux.vnet.ibm.com>,
Seth Jennings <sjenning@linux.vnet.ibm.com>,
Robert Jennings <rcj@linux.vnet.ibm.com>,
linuxppc-dev@lists.ozlabs.org
Subject: Re: tlb flushing on Power
Date: Thu, 26 Jan 2012 14:30:12 -0800 [thread overview]
Message-ID: <4F21D3F4.7020904@linux.vnet.ibm.com> (raw)
In-Reply-To: <1327613953.24487.9.camel@pasglop>
On 01/26/2012 01:39 PM, Benjamin Herrenschmidt wrote:
> Can you explain to me a bit more the whole business in this patch set
> about doing kmap_atomic() vs. manually trying to populate the PTEs ?
They're compressing pages and the allocator is trying getting very poor
packing of compressed pages in to PAGE_SIZE chunks. So, they're moving
to 2-page allocations that they need to be mapped contiguously to make
it easier on the users of the allocator.
> Why not just use two kmap atomic entries ? If interrupts are disabled
> kmap_atomic() should give you contiguous ones I suppose
I think you and I are at least on the same page on this one:
https://lkml.org/lkml/2012/1/26/355
> (unless NMIs are allowed to use kmap_atomic, are they ?)
Surely they can't be. Even if they could use it, they'd have to return
the __kmap_atomic_idx back to the place where it started before they
returned, so the interrupted code wouldn't notice.
next prev parent reply other threads:[~2012-01-26 22:30 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <4F2160B3.60708@linux.vnet.ibm.com>
2012-01-26 14:41 ` tlb flushing on Power Brian King
2012-01-26 21:39 ` Benjamin Herrenschmidt
2012-01-26 22:30 ` Dave Hansen [this message]
2012-01-27 2:40 ` Benjamin Herrenschmidt
2012-02-08 17:39 ` Seth Jennings
2012-02-08 21:04 ` Benjamin Herrenschmidt
2012-02-10 19:14 ` Seth Jennings
2012-02-16 17:11 ` Seth Jennings
2012-02-16 20:31 ` Benjamin Herrenschmidt
2012-03-05 17:56 ` Seth Jennings
2012-03-07 5:28 ` Michael Neuling
2012-03-07 21:18 ` Seth Jennings
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