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=-0.8 required=3.0 tests=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 89255C433E0 for ; Fri, 3 Jul 2020 21:52:08 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 4CB95207CD for ; Fri, 3 Jul 2020 21:52:08 +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="dAXQ/RS+" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4CB95207CD 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 CA7F28D0030; Fri, 3 Jul 2020 17:52:07 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id C583C8D0010; Fri, 3 Jul 2020 17:52:07 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id B6E1F8D0030; Fri, 3 Jul 2020 17:52:07 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0123.hostedemail.com [216.40.44.123]) by kanga.kvack.org (Postfix) with ESMTP id 9D11D8D0010 for ; Fri, 3 Jul 2020 17:52:07 -0400 (EDT) Received: from smtpin14.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id 280251EF1 for ; Fri, 3 Jul 2020 21:52:07 +0000 (UTC) X-FDA: 76998113094.14.day46_511732f26e95 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin14.hostedemail.com (Postfix) with ESMTP id F2DD718229818 for ; Fri, 3 Jul 2020 21:52:06 +0000 (UTC) X-HE-Tag: day46_511732f26e95 X-Filterd-Recvd-Size: 2508 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) by imf34.hostedemail.com (Postfix) with ESMTP for ; Fri, 3 Jul 2020 21:52:06 +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=lU/uXJfhXSguevBC4rPhh3n/kmpGM+LeT9/Wol7zCDc=; b=dAXQ/RS+LAD5awMVpxUelA7BoC fQVg4CTt+VJkOPEHeDwVj8fvvFP4LPQKX2q61FC6KeEc05mysCryWo0u2uLeov5UJD6AdsTEQ61ZS U7IrAd+eJoNXQIMXZ20JM0CcTBrFUWv10PyGb2e9RZujYKdDofSsYqK5vMjBb4mVw3tjev1YgNgqk fNebVhAOB0IdB6jDCyzN2TdACFanBC5KMFQaaFnmsKvYAQjGI9tjnYOx2PWOzdnxsg5AkshTPlt1P yoO0UxJIAs3jBJaH+PN2lSbj08GqBZmRAnq36r11lRvGoLf7l+1efGrl3yAUOsszlBOkhGcvjtsWp G6eYy6JQ==; Received: from willy by casper.infradead.org with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1jrTbB-0007Bf-Id; Fri, 03 Jul 2020 21:51:57 +0000 Date: Fri, 3 Jul 2020 22:51:57 +0100 From: Matthew Wilcox To: Uladzislau Rezki Cc: Linus Torvalds , peter enderborg , Linux Kernel Mailing List , Linux-MM , Andrew Morton , GregKroah-Hartmangregkh@linuxfoundation.org, Peter Zijlstra Subject: Re: nr_cpu_ids vs AMD 3970x(32 physical CPUs) Message-ID: <20200703215157.GI25523@casper.infradead.org> References: <20200703155749.GA6255@pc636> <8a2a55e6-6087-e4bf-3d35-ed4b4c216369@sony.com> <20200703192807.GB5207@pc636> <20200703212047.GA6856@pc636> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200703212047.GA6856@pc636> X-Rspamd-Queue-Id: F2DD718229818 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 Fri, Jul 03, 2020 at 11:20:47PM +0200, Uladzislau Rezki wrote: > Some background: > Actually i have been thinking about making vmalloc address space to > be per-CPU, i.e. divide it to per-CPU address space making an allocation > lock-less. It will eliminate a high lock contention. When i have done > a prototype i noticed and realized that there is a silly issue with > nr_cpu_ids on some systems. vfree() may happen on a different CPU from the one which called vmalloc(), so I'm not sure you're going to get as large a win as you think you will.