Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751093AbeABVJQ (ORCPT + 1 other); Tue, 2 Jan 2018 16:09:16 -0500 Received: from mail-io0-f180.google.com ([209.85.223.180]:32776 "EHLO mail-io0-f180.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751013AbeABVJO (ORCPT ); Tue, 2 Jan 2018 16:09:14 -0500 X-Google-Smtp-Source: ACJfBotEik2mta4YOinTy/C220hIRQrKShdKdqTf2XWxrowalechSrukK6fNSiAlHX6BL6eHPXf6mtr8x9Ilf5IKf1M= MIME-Version: 1.0 In-Reply-To: <20180102202859.4fvvrtngnitwzfym@alap3.anarazel.de> References: <20180102202859.4fvvrtngnitwzfym@alap3.anarazel.de> From: Linus Torvalds Date: Tue, 2 Jan 2018 13:09:13 -0800 X-Google-Sender-Auth: b29QeP2yGukDEJNVJWWJ1NMcFEs Message-ID: Subject: Re: Linux 4.15-rc6 To: Andres Freund Cc: Linux Kernel Mailing List Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Return-Path: On Tue, Jan 2, 2018 at 12:28 PM, Andres Freund wrote: > > I thought it'd be interesting to run a short benchmark to be able to > estimate the impact of the PTI work on postgres workloads (which I work > on). On my skylake laptop, a memory resident, OLTP workload with 16 > connections results in: Yeah, that's actually pretty much in line with expectations. Something around 5% performance impact of the isolation is what people are looking at. Obviously it depends on just exactly what you do. Some loads will hardly be affected at all, if they just spend all their time in user space. And if you do a lot of small system calls, you might see double-digit slowdowns. > This isn't a complaint, I just thought it might be useful > information. If it helps for anything/anybody, I'm happy to run > additional benchmarks / provide additional information. Note that it will depend heavily on the hardware too. Older CPU's without PCID will be impacted more by the isolation. And I think some of the back-ports won't take advantage of PCID even on newer hardware. Linus