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=-6.7 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED autolearn=unavailable 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 B3714C48BE8 for ; Mon, 24 Jun 2019 18:43:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 94CF420665 for ; Mon, 24 Jun 2019 18:43:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728094AbfFXSni (ORCPT ); Mon, 24 Jun 2019 14:43:38 -0400 Received: from mail-wr1-f65.google.com ([209.85.221.65]:35765 "EHLO mail-wr1-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726285AbfFXSnh (ORCPT ); Mon, 24 Jun 2019 14:43:37 -0400 Received: by mail-wr1-f65.google.com with SMTP id f15so5121461wrp.2 for ; Mon, 24 Jun 2019 11:43:36 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=GfjEkDFqzgTZBEb7tk5FQBBfhGJ6qrc4fpvCj0iHlvg=; b=PEMLzOlh0FhIICOnXDd6MnoSC8ODG7+U6KY9QYqdS6jTEuAtXQIYcUUCFm+Sb2VKKt XDH8PziZL5otFnWtD5c8J2FoKoOqOcXTVryoZKhROER/C4M8Un0+846X3PSCjTa5lQXB zU01u9ptz6jhB06mRWetGguL7wbGpRuZvj8d00WCds4RlMZ2cs7HpQ4POUU6ztIjzi84 874Z/7+2kuLAh6lmo0zx1fWXAzSUX4DsGPG7mGoMm12tTSc1sN2qhVjo/askcA0Ad3c2 tCPFPtdVQN98elu/Ehv1N71MQW8gdqZPqRF4zF1HSwxv34nUXLLVEZflX6UxlVm32Iiu B8rA== X-Gm-Message-State: APjAAAUIoHF83jiDzaFYBYsuMf9flFrn1PP33P+zwv+NiCiYJiLyOac9 JJ19fEiiprXfC7LDC52KQTZTfw== X-Google-Smtp-Source: APXvYqw37VJQFJbX+dUabx4CSUB5gIDbQkk/Rk2XlTrf2S7d3VSRR3BHYb/8IS7tK0hRyAS3jV9ftA== X-Received: by 2002:a5d:66ce:: with SMTP id k14mr45670884wrw.308.1561401815379; Mon, 24 Jun 2019 11:43:35 -0700 (PDT) Received: from ?IPv6:2001:b07:6468:f312:45fb:a0de:928e:79e8? ([2001:b07:6468:f312:45fb:a0de:928e:79e8]) by smtp.gmail.com with ESMTPSA id y19sm397750wmc.21.2019.06.24.11.43.33 (version=TLS1_3 cipher=AEAD-AES128-GCM-SHA256 bits=128/128); Mon, 24 Jun 2019 11:43:34 -0700 (PDT) Subject: Re: [PATCH v9 02/17] drivers/net/b44: Align pwol_mask to unsigned long for better performance To: David Laight , 'Fenghua Yu' , Thomas Gleixner , Ingo Molnar , Borislav Petkov , H Peter Anvin , Peter Zijlstra , Andrew Morton , Dave Hansen , Radim Krcmar , Christopherson Sean J , Ashok Raj , Tony Luck , Dan Williams , Xiaoyao Li , Sai Praneeth Prakhya , Ravi V Shankar Cc: linux-kernel , x86 , "kvm@vger.kernel.org" References: <1560897679-228028-1-git-send-email-fenghua.yu@intel.com> <1560897679-228028-3-git-send-email-fenghua.yu@intel.com> From: Paolo Bonzini Message-ID: <4cd9d48f-e655-4943-2ec9-1b74a77e317c@redhat.com> Date: Mon, 24 Jun 2019 20:43:32 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 24/06/19 17:12, David Laight wrote: > From: Fenghua Yu >> Sent: 18 June 2019 23:41 >> From: Peter Zijlstra >> >> A bit in pwol_mask is set in b44_magic_pattern() by atomic set_bit(). >> But since pwol_mask is local and never exposed to concurrency, there is >> no need to set bit in pwol_mask atomically. >> >> set_bit() sets the bit in a single unsigned long location. Because >> pwol_mask may not be aligned to unsigned long, the location may cross two >> cache lines. On x86, accessing two cache lines in locked instruction in >> set_bit() is called split locked access and can cause overall performance >> degradation. >> >> So use non atomic __set_bit() to set pwol_mask bits. __set_bit() won't hit >> split lock issue on x86. >> >> Signed-off-by: Peter Zijlstra >> Signed-off-by: Fenghua Yu >> --- >> drivers/net/ethernet/broadcom/b44.c | 4 ++-- >> 1 file changed, 2 insertions(+), 2 deletions(-) >> >> diff --git a/drivers/net/ethernet/broadcom/b44.c b/drivers/net/ethernet/broadcom/b44.c >> index 97ab0dd25552..5738ab963dfb 100644 >> --- a/drivers/net/ethernet/broadcom/b44.c >> +++ b/drivers/net/ethernet/broadcom/b44.c >> @@ -1520,7 +1520,7 @@ static int b44_magic_pattern(u8 *macaddr, u8 *ppattern, u8 *pmask, int offset) >> >> memset(ppattern + offset, 0xff, magicsync); >> for (j = 0; j < magicsync; j++) >> - set_bit(len++, (unsigned long *) pmask); >> + __set_bit(len++, (unsigned long *)pmask); >> >> for (j = 0; j < B44_MAX_PATTERNS; j++) { >> if ((B44_PATTERN_SIZE - len) >= ETH_ALEN) >> @@ -1532,7 +1532,7 @@ static int b44_magic_pattern(u8 *macaddr, u8 *ppattern, u8 *pmask, int offset) >> for (k = 0; k< ethaddr_bytes; k++) { >> ppattern[offset + magicsync + >> (j * ETH_ALEN) + k] = macaddr[k]; >> - set_bit(len++, (unsigned long *) pmask); >> + __set_bit(len++, (unsigned long *)pmask); > > Is this code expected to do anything sensible on BE systems? Probably not, but it's not wrong in different ways before/after the patch. Paolo > Casting the bitmask[] argument to any of the set_bit() functions is dubious at best.