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From: Ingo Molnar <mingo@kernel.org>
To: Dave Hansen <dave.hansen@linux.intel.com>
Cc: "Thomas Gleixner" <tglx@linutronix.de>,
	"Linus Torvalds" <torvalds@linux-foundation.org>,
	"Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>,
	linux-mm <linux-mm@kvack.org>,
	"Andrea Arcangeli" <aarcange@redhat.com>,
	"Andrew Lutomirski" <luto@kernel.org>,
	"Kees Cook" <keescook@google.com>,
	"Hugh Dickins" <hughd@google.com>,
	"Jürgen Groß" <jgross@suse.com>,
	"the arch/x86 maintainers" <x86@kernel.org>,
	namit@vmware.com
Subject: Re: [PATCH 00/11] Use global pages with PTI
Date: Fri, 30 Mar 2018 14:17:25 +0200	[thread overview]
Message-ID: <20180330121725.zcklh36ulg7crydw@gmail.com> (raw)
In-Reply-To: <20180330120920.btobga44wqytlkoe@gmail.com>


* Ingo Molnar <mingo@kernel.org> wrote:

> > 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%)
> > 
> > Lower is better here, obviously.
> > 
> > I also re-checked everything using will-it-scale's llseek1 test[2] which
> > is basically a microbenchmark of a halfway reasonable syscall.  Higher
> > here is better.
> > 
> > No Global pages (baseline): 15783951 lseeks/sec
> > 28 Global pages (this set): 16054688 lseeks/sec
> > 			     +270737 lseeks/sec (+1.71%)
> > 
> > So, both the kernel compile and the microbenchmark got measurably faster.
> 
> Ok, cool, this is much better!
> 
> Mind re-sending the patch-set against latest -tip so it can be merged?
> 
> At this point !PCID Intel hardware is not a primary concern, if something bad 
> happens on them with global pages we can quirk global pages off on them in some 
> way, or so.

BTW., the expectation on !PCID Intel hardware would be for global pages to help 
even more than the 0.6% and 1.7% you measured on PCID hardware: PCID already 
_reduces_ the cost of TLB flushes - so if there's not even PCID then global pages 
should help even more.

In theory at least. Would still be nice to measure it.

Thanks,

	Ingo

  reply	other threads:[~2018-03-30 12:17 UTC|newest]

Thread overview: 41+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-03-23 17:44 [PATCH 00/11] Use global pages with PTI Dave Hansen
2018-03-23 17:44 ` [PATCH 01/11] x86/mm: factor out pageattr _PAGE_GLOBAL setting Dave Hansen
2018-03-23 17:44 ` [PATCH 02/11] x86/mm: undo double _PAGE_PSE clearing Dave Hansen
2018-03-23 17:44 ` [PATCH 03/11] x86/mm: introduce "default" kernel PTE mask Dave Hansen
2018-03-23 17:44 ` [PATCH 04/11] x86/espfix: document use of _PAGE_GLOBAL Dave Hansen
2018-03-23 17:44 ` [PATCH 05/11] x86/mm: do not auto-massage page protections Dave Hansen
2018-03-23 19:15   ` Nadav Amit
2018-03-23 19:26     ` Dave Hansen
2018-03-23 19:26       ` Dave Hansen
2018-03-23 19:34       ` Nadav Amit
2018-03-23 19:38         ` Dave Hansen
2018-03-24 15:10   ` kbuild test robot
2018-03-24 15:10     ` kbuild test robot
2018-03-24 15:21   ` kbuild test robot
2018-03-24 15:21     ` kbuild test robot
2018-03-23 17:44 ` [PATCH 06/11] x86/mm: remove extra filtering in pageattr code Dave Hansen
2018-03-23 17:44 ` [PATCH 07/11] x86/mm: comment _PAGE_GLOBAL mystery Dave Hansen
2018-03-23 17:44 ` [PATCH 08/11] x86/mm: do not forbid _PAGE_RW before init for __ro_after_init Dave Hansen
2018-03-23 17:45 ` [PATCH 09/11] x86/pti: enable global pages for shared areas Dave Hansen
2018-03-23 19:12   ` Nadav Amit
2018-03-23 19:36     ` Dave Hansen
2018-03-23 17:45 ` [PATCH 10/11] x86/pti: clear _PAGE_GLOBAL for kernel image Dave Hansen
2018-03-23 17:45 ` [PATCH 11/11] x86/pti: leave kernel text global for !PCID Dave Hansen
2018-03-23 18:26 ` [PATCH 00/11] Use global pages with PTI Linus Torvalds
2018-03-24  0:40   ` Dave Hansen
2018-03-24  0:46     ` Linus Torvalds
2018-03-24  0:54       ` Linus Torvalds
2018-03-24 11:05     ` Ingo Molnar
2018-03-27 13:36     ` Thomas Gleixner
2018-03-27 16:32       ` Dave Hansen
2018-03-27 17:51         ` Thomas Gleixner
2018-03-27 20:07           ` Ingo Molnar
2018-03-27 20:19             ` Dave Hansen
2018-03-29  0:17             ` Dave Hansen
2018-03-30 12:09               ` Ingo Molnar
2018-03-30 12:17                 ` Ingo Molnar [this message]
2018-03-30 20:26                   ` Dave Hansen
2018-03-30 20:32                     ` Thomas Gleixner
2018-03-30 21:40                       ` Dave Hansen
2018-03-31  5:39                         ` Ingo Molnar
2018-03-31 18:19                           ` Dave Hansen

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