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

From	Dave Hansen <dave.hansen@intel.com>
Newsgroups	linux.kernel
Subject	Re: [RFC PATCH v2 2/3] xpfo: Only put previous userspace pages into the hot cache
Date	2016-09-02 22:40 +0200
Message-ID	<sd3pL-4ey-3@gated-at.bofh.it> (permalink)
References	<r6rz4-4yI-17@gated-at.bofh.it> <scUZc-7lv-9@gated-at.bofh.it> <scV8S-7oO-13@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On 09/02/2016 04:39 AM, Juerg Haefliger wrote:
> 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.

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?

Thread

[RFC PATCH v2 0/3] Add support for eXclusive Page Frame Ownership (XPFO) Juerg Haefliger <juerg.haefliger@hpe.com> - 2016-09-02 13:40 +0200
  [RFC PATCH v2 1/3] Add support for eXclusive Page Frame Ownership (XPFO) Juerg Haefliger <juerg.haefliger@hpe.com> - 2016-09-02 13:40 +0200
  [RFC PATCH v2 3/3] block: Always use a bounce buffer when XPFO is enabled Juerg Haefliger <juerg.haefliger@hpe.com> - 2016-09-02 13:50 +0200
  [RFC PATCH v2 2/3] xpfo: Only put previous userspace pages into the hot cache Juerg Haefliger <juerg.haefliger@hpe.com> - 2016-09-02 13:50 +0200
    Re: [RFC PATCH v2 2/3] xpfo: Only put previous userspace pages into  the hot cache Dave Hansen <dave.hansen@intel.com> - 2016-09-02 22:40 +0200
      Re: [RFC PATCH v2 2/3] xpfo: Only put previous userspace pages into  the hot cache Juerg Haefliger <juerg.haefliger@hpe.com> - 2016-09-05 14:00 +0200

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