From: Andy Lutomirski <luto@amacapital.net>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andy Lutomirski <luto@kernel.org>,
the arch/x86 maintainers <x86@kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Borislav Petkov <bp@alien8.de>, Brian Gerst <brgerst@gmail.com>,
Dave Hansen <dave.hansen@linux.intel.com>,
Oleg Nesterov <oleg@redhat.com>,
"linux-mm@kvack.org" <linux-mm@kvack.org>
Subject: Re: [RFC 00/13] x86/mm: PCID and INVPCID
Date: Fri, 8 Jan 2016 15:36:13 -0800 [thread overview]
Message-ID: <CALCETrXEe0shSz25oB7yk4Ee5+y3AZJ6Kt3SANeBsmLCO7StKg@mail.gmail.com> (raw)
In-Reply-To: <CA+55aFxpGj2koqmcFF9JWzBeheF9473Ka516shwbuhfjVpgxrg@mail.gmail.com>
On Fri, Jan 8, 2016 at 3:31 PM, Linus Torvalds
<torvalds@linux-foundation.org> wrote:
> On Fri, Jan 8, 2016 at 3:15 PM, Andy Lutomirski <luto@kernel.org> wrote:
>>
>> Please play around and suggest (and run?) good benchmarks. It seems
>> to save around 100ns on cross-process context switches for me.
>
> Interesting. There was reportedly (I never saw it) a test-patch to use
> pcids inside of Intel a couple of years ago, and it never got outside
> because it didn't make a difference.
I have a copy of that patch, and my code works very differently. I
only use 3 bits of PCID in this series. I could probably reduce that
to 2 with little loss. 4 or more would be a waste.
>
> Either things have changed (newer hardware with more pcids perhaps?)
> or you did a better job at it.
On my Skylake laptop, all of the PCID bits appear to have at least
some effect. Whether this means it gets hashed or whether this means
that all of the bits are real, I don't know. I'll fiddle with it on
an older machine.
--Andy
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next prev parent reply other threads:[~2016-01-08 23:36 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-01-08 23:15 Andy Lutomirski
2016-01-08 23:15 ` [RFC 01/13] x86/paravirt: Turn KASAN off for parvirt.o Andy Lutomirski
2016-01-10 18:59 ` Borislav Petkov
2016-01-11 12:51 ` Andrey Ryabinin
2016-01-11 12:51 ` [PATCH 1/2] x86/kasan: clear kasan_zero_page after TLB flush Andrey Ryabinin
2016-01-18 22:24 ` Andy Lutomirski
2016-01-11 12:51 ` [PATCH 2/2] x86/kasan: write protect kasan zero shadow Andrey Ryabinin
2016-01-18 22:24 ` Andy Lutomirski
2016-01-29 10:35 ` [RFC 01/13] x86/paravirt: Turn KASAN off for parvirt.o Borislav Petkov
2016-01-08 23:15 ` [RFC 02/13] x86/mm: Add INVPCID helpers Andy Lutomirski
2016-01-08 23:15 ` [RFC 03/13] x86/mm: Add a noinvpcid option to turn off INVPCID Andy Lutomirski
2016-01-08 23:15 ` [RFC 04/13] x86/mm: If INVPCID is available, use it to flush global mappings Andy Lutomirski
2016-01-08 23:15 ` [RFC 05/13] x86/mm: Add barriers and document switch_mm-vs-flush synchronization Andy Lutomirski
2016-06-03 17:42 ` Nadav Amit
2016-06-09 17:24 ` Andy Lutomirski
2016-06-09 19:45 ` Nadav Amit
2016-09-06 1:22 ` Wanpeng Li
2016-01-08 23:15 ` [RFC 06/13] x86/mm: Disable PCID on 32-bit kernels Andy Lutomirski
2016-01-08 23:15 ` [RFC 07/13] x86/mm: Add nopcid to turn off PCID Andy Lutomirski
2016-01-08 23:15 ` [RFC 08/13] x86/mm: Teach CR3 readers about PCID Andy Lutomirski
2016-01-08 23:15 ` [RFC 09/13] x86/mm: Disable interrupts when flushing the TLB using CR3 Andy Lutomirski
2016-01-08 23:41 ` Linus Torvalds
2016-01-09 0:18 ` Andy Lutomirski
2016-01-09 2:20 ` Linus Torvalds
2016-01-11 10:51 ` Ingo Molnar
2016-01-13 23:32 ` Andy Lutomirski
2016-01-13 23:35 ` Andy Lutomirski
2016-01-13 23:43 ` Dave Hansen
2016-01-13 23:51 ` Andy Lutomirski
2016-01-13 23:56 ` Dave Hansen
2016-01-14 0:34 ` Andy Lutomirski
2016-01-08 23:15 ` [RFC 10/13] x86/mm: Factor out remote TLB flushing Andy Lutomirski
2016-01-08 23:15 ` [RFC 11/13] x86/mm: Build arch/x86/mm/tlb.c even on !SMP Andy Lutomirski
2016-01-08 23:55 ` Dave Hansen
2016-01-08 23:15 ` [RFC 12/13] x86/mm: Uninline switch_mm Andy Lutomirski
2016-01-08 23:15 ` [RFC 13/13] x86/mm: Try to preserve old TLB entries using PCID Andy Lutomirski
2016-01-09 0:27 ` Dave Hansen
2016-01-09 2:19 ` Andy Lutomirski
2016-01-08 23:31 ` [RFC 00/13] x86/mm: PCID and INVPCID Linus Torvalds
2016-01-08 23:36 ` Andy Lutomirski [this message]
2016-01-08 23:42 ` Linus Torvalds
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