From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-3.8 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 965C1C433E0 for ; Tue, 14 Jul 2020 13:23:55 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 3ACEC2242C for ; Tue, 14 Jul 2020 13:23:55 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="Kh3uWg7u" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3ACEC2242C Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 6D3046B0003; Tue, 14 Jul 2020 09:23:54 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 65CEF6B0005; Tue, 14 Jul 2020 09:23:54 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 4FD8F6B0006; Tue, 14 Jul 2020 09:23:54 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0037.hostedemail.com [216.40.44.37]) by kanga.kvack.org (Postfix) with ESMTP id 3ACE76B0003 for ; Tue, 14 Jul 2020 09:23:54 -0400 (EDT) Received: from smtpin21.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id 9CE571EF1 for ; Tue, 14 Jul 2020 13:23:53 +0000 (UTC) X-FDA: 77036749146.21.boat01_25110b226ef1 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin21.hostedemail.com (Postfix) with ESMTP id 608C7180442C0 for ; Tue, 14 Jul 2020 13:23:53 +0000 (UTC) X-HE-Tag: boat01_25110b226ef1 X-Filterd-Recvd-Size: 2969 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) by imf30.hostedemail.com (Postfix) with ESMTP for ; Tue, 14 Jul 2020 13:23:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=T7rggtXykXMc4C3uWwX+AsNgDJpkydxTqpZAtzGfPZw=; b=Kh3uWg7u8XQglQ4xrw+ceXYX8S CWYZSH7s+NgPkTUhlq3N/9wlFTdrJWTUnC9eq/G9rVKsKpa3nSNgKcvTJyVzIzkn5nUzA/PZoDzoU dLfUT4nS8snnIwOWcrOzkVucwrUhbZdhbvN+5Dr/QZ+Asez6AXurhhpzMkQ2139xhUsSPU2xWIIQQ 7gxe6uFmEEyfFAzvaexTRkN7d5JSEbyo9mJKoddyBTvgQyAvEWHAF6x06dSySkk64A+k4SRf2+Nf6 wB4G28sTRoDwXUGqj2sP0qL2DpJotZ27Aa94peKoOJ0bT/0WvZ+cCmHU5fXW+e2BbzVlAJRePIXXd TkX/DowA==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1jvKuM-0004mD-H6; Tue, 14 Jul 2020 13:23:42 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id BF165302753; Tue, 14 Jul 2020 15:23:41 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id AB5BC2BE34E09; Tue, 14 Jul 2020 15:23:41 +0200 (CEST) Date: Tue, 14 Jul 2020 15:23:41 +0200 From: Peter Zijlstra To: Andy Lutomirski Cc: Nicholas Piggin , Anton Blanchard , Arnd Bergmann , linux-arch , LKML , Linux-MM , linuxppc-dev , Andy Lutomirski , Mathieu Desnoyers , X86 ML Subject: Re: [RFC PATCH 7/7] lazy tlb: shoot lazies, a non-refcounting lazy tlb option Message-ID: <20200714132341.GY10769@hirez.programming.kicks-ass.net> References: <1594708054.04iuyxuyb5.astroid@bobo.none> <6D3D1346-DB1E-43EB-812A-184918CCC16A@amacapital.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <6D3D1346-DB1E-43EB-812A-184918CCC16A@amacapital.net> X-Rspamd-Queue-Id: 608C7180442C0 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam02 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue, Jul 14, 2020 at 05:46:05AM -0700, Andy Lutomirski wrote: > x86 has this exact problem. At least no more than 64*8 CPUs share the cache line :) I've seen patches for a 'sparse' bitmap to solve related problems. It's basically the same code, except it multiplies everything (size, bit-nr) by a constant to reduce the number of active bits per line. This sadly doesn't take topology into account, but reducing contention is still good ofcourse.