From mboxrd@z Thu Jan  1 00:00:00 1970
From: David Ahern <dsahern@gmail.com>
Subject: Re: [PATCH net-next v2] net: core: change bool members of struct
 net_device to bitfield members
Date: Tue, 9 Oct 2018 14:43:27 -0600
Message-ID: <f8bbbd11-0ad2-77e6-c4fe-e3f643e7e243@gmail.com>
References: <e0150624-a317-eb4f-126e-92c99db8ce13@gmail.com>
 <35349fe9-94ac-e2d0-f02c-078c9fd58090@gmail.com>
 <ded0a778-ca20-4e0f-223d-da3eb5cd71b2@gmail.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: 7bit
Cc: "netdev@vger.kernel.org" <netdev@vger.kernel.org>,
        David Laight <David.Laight@ACULAB.COM>
To: Heiner Kallweit <hkallweit1@gmail.com>,
        David Miller <davem@davemloft.net>
Return-path: <netdev-owner@vger.kernel.org>
Received: from mail-pg1-f196.google.com ([209.85.215.196]:33205 "EHLO
        mail-pg1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
        with ESMTP id S1725748AbeJJECO (ORCPT
        <rfc822;netdev@vger.kernel.org>); Wed, 10 Oct 2018 00:02:14 -0400
Received: by mail-pg1-f196.google.com with SMTP id y18-v6so1402930pge.0
        for <netdev@vger.kernel.org>; Tue, 09 Oct 2018 13:43:29 -0700 (PDT)
In-Reply-To: <ded0a778-ca20-4e0f-223d-da3eb5cd71b2@gmail.com>
Content-Language: en-US
Sender: netdev-owner@vger.kernel.org
List-ID: <netdev.vger.kernel.org>

On 10/9/18 2:24 PM, Heiner Kallweit wrote:
> Reordering the struct members to fill the holes could be a little tricky
> and could have side effects because it may make a performance difference
> whether certain members are in one cacheline or not.
> And whether it's worth to spend this effort (incl. the related risks)
> just to save a few bytes (also considering that typically we have quite
> few instances of struct net_device)?
> 

It would be good to get net_device below 2048 without affecting
performance. Anything else is just moving elements around for the same
end allocation (rounds up to 4096).