Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752584AbdFNWsd (ORCPT ); Wed, 14 Jun 2017 18:48:33 -0400 Received: from mail.kernel.org ([198.145.29.99]:50162 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752376AbdFNWsb (ORCPT ); Wed, 14 Jun 2017 18:48:31 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 19AE4239E0 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=luto@kernel.org MIME-Version: 1.0 In-Reply-To: <6da4aea9-ef52-694d-9a03-285c32018326@intel.com> References: <6da4aea9-ef52-694d-9a03-285c32018326@intel.com> From: Andy Lutomirski Date: Wed, 14 Jun 2017 15:48:09 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v2 00/10] PCID and improved laziness To: Dave Hansen Cc: Andy Lutomirski , X86 ML , "linux-kernel@vger.kernel.org" , Borislav Petkov , Linus Torvalds , Andrew Morton , Mel Gorman , "linux-mm@kvack.org" , Nadav Amit , Rik van Riel , Arjan van de Ven , Peter Zijlstra Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 900 Lines: 17 On Wed, Jun 14, 2017 at 3:18 PM, Dave Hansen wrote: > On 06/13/2017 09:56 PM, Andy Lutomirski wrote: >> 2. Mms that have been used recently on a given CPU might get to keep >> their TLB entries alive across process switches with this patch >> set. TLB fills are pretty fast on modern CPUs, but they're even >> faster when they don't happen. > > Let's not forget that TLBs are also getting bigger. The bigger TLBs > help ensure that they *can* survive across another process's timeslice. > > Also, the cost to refill the paging structure caches is going up. Just > think of how many cachelines you have to pull in to populate a > ~1500-entry TLB, even if the CPU hid the latency of those loads. Then throw EPT into the mix for extra fun. I wonder if we should try to allocate page tables from nearby physical addresses if we think we might be running as a guest.