From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752406AbdFVFTy (ORCPT ); Thu, 22 Jun 2017 01:19:54 -0400 Received: from mail.kernel.org ([198.145.29.99]:41904 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751064AbdFVFTx (ORCPT ); Thu, 22 Jun 2017 01:19:53 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 74E7822B6A 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: References: From: Andy Lutomirski Date: Wed, 21 Jun 2017 22:19:30 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v3 00/11] PCID and improved laziness To: Linus Torvalds Cc: Andy Lutomirski , "the arch/x86 maintainers" , Linux Kernel Mailing List , Borislav Petkov , Andrew Morton , Mel Gorman , "linux-mm@kvack.org" , Nadav Amit , Rik van Riel , Dave Hansen , 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 On Wed, Jun 21, 2017 at 11:23 AM, Linus Torvalds wrote: > On Tue, Jun 20, 2017 at 10:22 PM, Andy Lutomirski wrote: >> There are three performance benefits here: > > Side note: can you post the actual performance numbers, even if only > from some silly test program on just one platform? Things like lmbench > pipe benchmark or something? > > Or maybe you did, and I just missed it. But when talking about > performance, I'd really like to always see some actual numbers. Here are some timings using KVM: pingpong between two processes using eventfd: patched: 883ns unpatched: 1046ns (with considerably higher variance) madvise(MADV_DONTNEED); write to the page; switch CPUs: patched: ~12.5us unpatched: 19us The latter test is a somewhat contrived example to show off the improved laziness. Current kernels send an IPI on each iteration if the system is otherwise idle. From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ot0-f199.google.com (mail-ot0-f199.google.com [74.125.82.199]) by kanga.kvack.org (Postfix) with ESMTP id 133E46B0279 for ; Thu, 22 Jun 2017 01:19:54 -0400 (EDT) Received: by mail-ot0-f199.google.com with SMTP id 37so4385797otu.13 for ; Wed, 21 Jun 2017 22:19:54 -0700 (PDT) Received: from mail.kernel.org (mail.kernel.org. [198.145.29.99]) by mx.google.com with ESMTPS id u4si171190otf.87.2017.06.21.22.19.53 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 21 Jun 2017 22:19:53 -0700 (PDT) Received: from mail-ua0-f182.google.com (mail-ua0-f182.google.com [209.85.217.182]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 6F18822B67 for ; Thu, 22 Jun 2017 05:19:52 +0000 (UTC) Received: by mail-ua0-f182.google.com with SMTP id z22so5722570uah.1 for ; Wed, 21 Jun 2017 22:19:52 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: References: From: Andy Lutomirski Date: Wed, 21 Jun 2017 22:19:30 -0700 Message-ID: Subject: Re: [PATCH v3 00/11] PCID and improved laziness Content-Type: text/plain; charset="UTF-8" Sender: owner-linux-mm@kvack.org List-ID: To: Linus Torvalds Cc: Andy Lutomirski , the arch/x86 maintainers , Linux Kernel Mailing List , Borislav Petkov , Andrew Morton , Mel Gorman , "linux-mm@kvack.org" , Nadav Amit , Rik van Riel , Dave Hansen , Arjan van de Ven , Peter Zijlstra On Wed, Jun 21, 2017 at 11:23 AM, Linus Torvalds wrote: > On Tue, Jun 20, 2017 at 10:22 PM, Andy Lutomirski wrote: >> There are three performance benefits here: > > Side note: can you post the actual performance numbers, even if only > from some silly test program on just one platform? Things like lmbench > pipe benchmark or something? > > Or maybe you did, and I just missed it. But when talking about > performance, I'd really like to always see some actual numbers. Here are some timings using KVM: pingpong between two processes using eventfd: patched: 883ns unpatched: 1046ns (with considerably higher variance) madvise(MADV_DONTNEED); write to the page; switch CPUs: patched: ~12.5us unpatched: 19us The latter test is a somewhat contrived example to show off the improved laziness. Current kernels send an IPI on each iteration if the system is otherwise idle. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org