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=-2.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 81ED9C2D0C8 for ; Fri, 20 Dec 2019 16:34:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 565B7206D3 for ; Fri, 20 Dec 2019 16:34:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1576859686; bh=vv0t1eGOsgj4AJRjK2Vg7hvSuEzjKLFQEXcZQpwhYK4=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=qm18T6RCkD1B0PlqNr4GQ/JnOOZV23HgOSPqBNwwV2MJVJgflXQFV/GvcmWzXg2PP 3VW4F5E59BZQP04TKbollZwabsqu+6TLnrvMIyl/8LbhqWHunHgvCWQmCP4Y23SaBY l/1HjOeadoZAvX52VXbC7xm3985WL4SW3Jun/kSo= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727421AbfLTQep (ORCPT ); Fri, 20 Dec 2019 11:34:45 -0500 Received: from mail-qt1-f176.google.com ([209.85.160.176]:45902 "EHLO mail-qt1-f176.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726808AbfLTQeo (ORCPT ); Fri, 20 Dec 2019 11:34:44 -0500 Received: by mail-qt1-f176.google.com with SMTP id l12so8645831qtq.12; Fri, 20 Dec 2019 08:34:44 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=sender:date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=s2wiG4V9nXDcYp93nFV8wxg+pKyytXlurRJn0olF8cc=; b=mEbQsjqJ1j16fUpahYOimus1B1lnXLMQnQLpFURegX8v17kvx4s6H+uyrHvLcriQav 2lEpXor9io+tIVsXk8R0U2mbpNkNgMau9xFmqOycHTIItkTdYgUzzcOUzYXovW4nRvMk nKiT2Kq7R/hWzTH22vxLdKvCyzF/3WCFjHjOmgOm6oflj4gY9oDtpQe0/LIuzM/KjXSd QcaPnUUNDaZtR5palhizK4VrANl7sPB3suRw2PUu/vJdDUKcVMoP6wqDP5goo6mmImxR PDLu11WprAKnGdVb/skReG0K3eSPOFO70nWhNdDkHrq5nY+potj3utsjOyqlg4tjhbAT hMYw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:sender:date:from:to:cc:subject:message-id :references:mime-version:content-disposition:in-reply-to:user-agent; bh=s2wiG4V9nXDcYp93nFV8wxg+pKyytXlurRJn0olF8cc=; b=XeVGYr9onpf8sCYIdliI1b6YMhnMZICWXf+lkZjsY6tX6afPBhj/eWMkVBNgPTp0v4 S7TRK21tXeBjKz4n+frY9mL+gpIKKLtoZ3x5SgL0VA+x6Kv/kbr5R0xwmL9RqisK55jQ 36FdcIJ9DRzOlGsB+fk14HCLAypZTXGKV9pgO+tPFY6ouML3kSACPCFBYHD2fAJLPaVm YzYA0OP+C+0uGL2vM/P/AFMZAaLh8ql53Lg4diFiOl+KA5XW30x4Rbq2jyT9Zi2hR8VV +BbjYtXDM9zTEpX7fC9d1Uj1weUjKpSsZ9Jd4fpy5Dp2qjxysTWZ9YK+MII6EibCywtt JiYQ== X-Gm-Message-State: APjAAAV1FPMCx1hV7HnbAw18RJkWlfOiSHkH+6lTf4byG+NHErzToV5F 7Sn0zpZSEfoKO85aP1KvUAEw5nawChc= X-Google-Smtp-Source: APXvYqxdTmROGq8u9t4V757dBQhddzRsHPWWCpr8nAsfRAHDN4P5YIulIFC17B7dIk8wXNeH2wR1dA== X-Received: by 2002:ac8:664a:: with SMTP id j10mr12215392qtp.70.1576859683642; Fri, 20 Dec 2019 08:34:43 -0800 (PST) Received: from localhost ([2620:10d:c091:480::11e7]) by smtp.gmail.com with ESMTPSA id x126sm2955357qkc.42.2019.12.20.08.34.42 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 20 Dec 2019 08:34:43 -0800 (PST) Date: Fri, 20 Dec 2019 08:34:41 -0800 From: Tejun Heo To: Eric Dumazet Cc: Jesper Dangaard Brouer , =?iso-8859-1?Q?Bj=F6rn_T=F6pel?= , bpf , LKML , Christoph Lameter , Dennis Zhou Subject: Re: Percpu variables, benchmarking, and performance weirdness Message-ID: <20191220163441.GH2914998@devbig004.ftw2.facebook.com> References: <20191220103420.6f9304ab@carbon> <20191220151239.GE2914998@devbig004.ftw2.facebook.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Dec 20, 2019 at 08:22:02AM -0800, Eric Dumazet wrote: > I definitely seen expensive per-cpu updates in the stack. > (SNMP counters, or per-cpu stats for packets/bytes counters) > > It might be nice to have an option to use 2M pages. > > (I recall sending some patches in the past about using high-order pages for vmalloc, > but this went nowhere) Yeah, the percpu allocator implementation is half-way prepared for that. There just hasn't been a real need for that yet. If this actually is a difference coming from tlb pressure, this might be it, I guess? Thanks. -- tejun