From: Dave Hansen <dave.hansen@linux.intel.com>
To: linux-kernel@vger.kernel.org
Cc: linux-mm@kvack.org, Dave Hansen <dave.hansen@linux.intel.com>,
aarcange@redhat.com, luto@kernel.org,
torvalds@linux-foundation.org, keescook@google.com,
hughd@google.com, jgross@suse.com, x86@kernel.org,
namit@vmware.com
Subject: [PATCH 00/11] [v3] Use global pages with PTI
Date: Mon, 02 Apr 2018 10:27:00 -0700 [thread overview]
Message-ID: <20180402172700.65CAE838@viggo.jf.intel.com> (raw)
Changes from v2:
* Add performance numbers to changelogs
* Fix compile error resulting from use of x86-specific
__default_kernel_pte_mask in arch-generic mm/early_ioremap.c
* Delay kernel text cloning until after we are done messing
with it (patch 11).
* Blacklist K8 explicitly from mapping all kernel text as
global (this should never happen because K8 does not use
pti when pti=auto, but we on the safe side). (patch 11)
--
The later versions of the KAISER patches (pre-PTI) allowed the
user/kernel shared areas to be GLOBAL. The thought was that this would
reduce the TLB overhead of keeping two copies of these mappings.
During the switch over to PTI, we seem to have lost our ability to have
GLOBAL mappings. This adds them back.
To measure the benefits of this, I took a modern Atom system without
PCIDs and ran a microbenchmark[1] (higher is better):
No Global Lines (baseline ): 6077741 lseeks/sec
88 Global Lines (kern entry): 7528609 lseeks/sec (+23.9%)
94 Global Lines (all ktext ): 8433111 lseeks/sec (+38.8%)
On a modern Skylake desktop with PCIDs, the benefits are tangible, but not
huge:
No Global pages (baseline): 15783951 lseeks/sec
28 Global pages (this set): 16054688 lseeks/sec
+270737 lseeks/sec (+1.71%)
I also double-checked with a kernel compile on the Skylake system (lower
is better):
No Global pages (baseline): 186.951 seconds time elapsed ( +- 0.35% )
28 Global pages (this set): 185.756 seconds time elapsed ( +- 0.09% )
-1.195 seconds (-0.64%)
1. https://github.com/antonblanchard/will-it-scale/blob/master/tests/lseek1.c
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Kees Cook <keescook@google.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: x86@kernel.org
Cc: Nadav Amit <namit@vmware.com>
next reply other threads:[~2018-04-02 17:29 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-04-02 17:27 Dave Hansen [this message]
2018-04-02 17:27 ` [PATCH 01/11] x86/mm: factor out pageattr _PAGE_GLOBAL setting Dave Hansen
2018-04-02 17:52 ` Linus Torvalds
2018-04-02 20:23 ` Dave Hansen
2018-04-02 17:27 ` [PATCH 02/11] x86/mm: undo double _PAGE_PSE clearing Dave Hansen
2018-04-02 17:27 ` [PATCH 03/11] x86/mm: introduce "default" kernel PTE mask Dave Hansen
2018-04-02 17:27 ` [PATCH 04/11] x86/espfix: document use of _PAGE_GLOBAL Dave Hansen
2018-04-02 17:27 ` [PATCH 05/11] x86/mm: do not auto-massage page protections Dave Hansen
2018-04-02 17:27 ` [PATCH 06/11] x86/mm: remove extra filtering in pageattr code Dave Hansen
2018-04-02 17:27 ` [PATCH 07/11] x86/mm: comment _PAGE_GLOBAL mystery Dave Hansen
2018-04-02 17:27 ` [PATCH 08/11] x86/mm: do not forbid _PAGE_RW before init for __ro_after_init Dave Hansen
2018-04-02 17:27 ` [PATCH 09/11] x86/pti: enable global pages for shared areas Dave Hansen
2018-04-02 17:56 ` Linus Torvalds
2018-04-02 20:41 ` Dave Hansen
2018-04-02 17:27 ` [PATCH 10/11] x86/pti: never implicitly clear _PAGE_GLOBAL for kernel image Dave Hansen
2018-04-02 17:27 ` [PATCH 11/11] x86/pti: leave kernel text global for !PCID Dave Hansen
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20180402172700.65CAE838@viggo.jf.intel.com \
--to=dave.hansen@linux.intel.com \
--cc=aarcange@redhat.com \
--cc=hughd@google.com \
--cc=jgross@suse.com \
--cc=keescook@google.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=luto@kernel.org \
--cc=namit@vmware.com \
--cc=torvalds@linux-foundation.org \
--cc=x86@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).