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From: Dave Hansen <dave.hansen@linux.intel.com>
To: Andy Lutomirski <luto@kernel.org>,
	x86@kernel.org, linux-kernel@vger.kernel.org
Cc: Borislav Petkov <bp@alien8.de>, Brian Gerst <brgerst@gmail.com>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Oleg Nesterov <oleg@redhat.com>,
	"linux-mm@kvack.org" <linux-mm@kvack.org>
Subject: Re: [RFC 13/13] x86/mm: Try to preserve old TLB entries using PCID
Date: Fri, 8 Jan 2016 16:27:37 -0800	[thread overview]
Message-ID: <569053F9.7060002@linux.intel.com> (raw)
In-Reply-To: <c4125ff6333c97d3ce00e5886b809b7c20594585.1452294700.git.luto@kernel.org>

On 01/08/2016 03:15 PM, Andy Lutomirski wrote:
> + * The guiding principle of this code is that TLB entries that have
> + * survived more than a small number of context switches are mostly
> + * useless, so we don't try very hard not to evict them.

Big ack on that.  The original approach tried to keep track of the full
4k worth of possible PCIDs, it also needed an additional cpumask (which
it dynamically allocated) for where the PCID was active in addition to
the normal "where has this mm been" mask.

That's a lot of extra data to mangle, and I can definitely see your
approach as being nicer, *IF* the hardware isn't doing something useful
with the other 9 bits of PCID that you're throwing away. ;)

  reply	other threads:[~2016-01-09  0:27 UTC|newest]

Thread overview: 43+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-01-08 23:15 [RFC 00/13] x86/mm: PCID and INVPCID 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
2016-02-09 16:06         ` [tip:x86/mm] x86/kasan: Clear " tip-bot for Andrey Ryabinin
2016-01-11 12:51       ` [PATCH 2/2] x86/kasan: write protect kasan zero shadow Andrey Ryabinin
2016-01-18 22:24         ` Andy Lutomirski
2016-02-09 16:07         ` [tip:x86/mm] x86/kasan: Write " tip-bot for Andrey Ryabinin
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 [this message]
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
2016-01-08 23:42     ` Linus Torvalds

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