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
next prev parent reply other threads:[~2018-03-30 12:17 UTC|newest]
Thread overview: 38+ 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 19:34 ` Nadav Amit
2018-03-23 19:38 ` Dave Hansen
2018-03-24 15:10 ` 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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