Thread (37 messages) 37 messages, 9 authors, 2016-12-09

Re: [kernel-hardening] [RFC PATCH v2 2/3] xpfo: Only put previous userspace pages into the hot cache

From: Juerg Haefliger <hidden>
Date: 2016-09-14 14:41:01
Also in: lkml

Hi Dave,

On 09/14/2016 04:33 PM, Dave Hansen wrote:
On 09/14/2016 12:19 AM, Juerg Haefliger wrote:
quoted
Allocating a page to userspace that was previously allocated to the
kernel requires an expensive TLB shootdown. To minimize this, we only
put non-kernel pages into the hot cache to favor their allocation.
Hi, I had some questions about this the last time you posted it.  Maybe
you want to address them now.
I did reply: https://lkml.org/lkml/2016/9/5/249

...Juerg

--

But kernel allocations do allocate from these pools, right?  Does this
just mean that kernel allocations usually have to pay the penalty to
convert a page?

So, what's the logic here?  You're assuming that order-0 kernel
allocations are more rare than allocations for userspace?
  

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