Received: by 2002:a05:6a10:9848:0:0:0:0 with SMTP id x8csp1097751pxf; Thu, 18 Mar 2021 21:18:56 -0700 (PDT) X-Google-Smtp-Source: ABdhPJxgCbP9DSHAftXcawHMtGuKNv4xsrbEDrqCiW3fxNqAei/Ji0R/NkqrLnLdJh8Z8O80XIQ1 X-Received: by 2002:a05:6402:1115:: with SMTP id u21mr7375779edv.383.1616127536368; Thu, 18 Mar 2021 21:18:56 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1616127536; cv=none; d=google.com; s=arc-20160816; b=ZufQG+qmHjhO1453vZleaUfw3q6xMoAZ6K5w5sDZ1rNmCczzboNzyU0Mvnca6/NxSx RU/LEQA6cZhjxUVvcmyng28DRpzU0OguWpAVgntvQ7w038fBnODQgvEvB/+rd6nUwIAa coCUIidyQKL1efgSYFijDKDGyvFd3izvKrbxiInGWDzwfToVVr/YnC00NVMiDry4DcaQ dzpPQ4Z32TRIRlsnsLB+rhEH57DYMHD2R1NXGk+zDkeb628K8OvfLt9lekmx0CR/WvSq 25YfIrbYrSKYlFrUqEwYzUtl06f5NR9HZENqxiXRUJdPC5txoCEw4jGSDnGC/g5wcvss sfMA== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:user-agent:in-reply-to:content-disposition :mime-version:references:message-id:subject:cc:to:from:date; bh=c6fmlSbalZXfi432BsDUsDbzpRfnKhVObiJZ/KOShUc=; b=mSpZcwz6pZo/61ASuLBVxYxW+K1/GToFxsg04wX+35ZlBw0XxU5hhrEdByfuB1StDA DJhayMvrczOdor0EeuwDa2TzNxj3LeOqD5J0K7tf+NGpkK2HN4GgcVfB59mNSLlaGJ04 s8Q1v5cerFB/ho7y4MsXcPcGhaoh9ZI2zrO1m2JKHNOfDKZGrc3WWT2MXD64DTYtq8qB FdarXXeIYBXkGmB8z4yUhop/BvGOUOMvf/M9TkEQRECaQZVxt1/kinar5+xgINxG0+Rp iRjyoYkqKL1rH5lAz8Zs/E7MltxtQdILLuiZJFFsDO+180LHmVU8j9mr8G+8IyRh7RU7 iH4A== ARC-Authentication-Results: i=1; mx.google.com; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Return-Path: Received: from vger.kernel.org (vger.kernel.org. [23.128.96.18]) by mx.google.com with ESMTP id f24si3244621ejz.234.2021.03.18.21.18.33; Thu, 18 Mar 2021 21:18:56 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18; Authentication-Results: mx.google.com; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233626AbhCSEQB (ORCPT + 99 others); Fri, 19 Mar 2021 00:16:01 -0400 Received: from wtarreau.pck.nerim.net ([62.212.114.60]:50580 "EHLO 1wt.eu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231599AbhCSEPp (ORCPT ); Fri, 19 Mar 2021 00:15:45 -0400 Received: (from willy@localhost) by pcw.home.local (8.15.2/8.15.2/Submit) id 12J4FZJ4003460; Fri, 19 Mar 2021 05:15:35 +0100 Date: Fri, 19 Mar 2021 05:15:35 +0100 From: Willy Tarreau To: Sieng Piaw Liew Cc: chris.snook@gmail.com, davem@davemloft.net, kuba@kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] atl1c: optimize rx loop Message-ID: <20210319041535.GA3441@1wt.eu> References: <20210319040447.527-1-liew.s.piaw@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210319040447.527-1-liew.s.piaw@gmail.com> User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Mar 19, 2021 at 12:04:47PM +0800, Sieng Piaw Liew wrote: > Remove this trivial bit of inefficiency from the rx receive loop, > results in increase of a few Mbps in iperf3. Tested on Intel Core2 > platform. > > Signed-off-by: Sieng Piaw Liew > --- > drivers/net/ethernet/atheros/atl1c/atl1c_main.c | 4 +--- > 1 file changed, 1 insertion(+), 3 deletions(-) > > diff --git a/drivers/net/ethernet/atheros/atl1c/atl1c_main.c b/drivers/net/ethernet/atheros/atl1c/atl1c_main.c > index 3f65f2b370c5..b995f9a0479c 100644 > --- a/drivers/net/ethernet/atheros/atl1c/atl1c_main.c > +++ b/drivers/net/ethernet/atheros/atl1c/atl1c_main.c > @@ -1796,9 +1796,7 @@ static void atl1c_clean_rx_irq(struct atl1c_adapter *adapter, > struct atl1c_recv_ret_status *rrs; > struct atl1c_buffer *buffer_info; > > - while (1) { > - if (*work_done >= work_to_do) > - break; > + while (*work_done < work_to_do) { It should not change anything, or only based on the compiler's optimization and should not result in a measurable difference because what it does is exactly the same. Have you really compared the compiled output code to explain the difference ? I strongly suspect you'll find no difference at all. Thus for me it's certainly not an optimization, it could be qualified as a cleanup to improve code readability however. Willy