netdev - Re: [PATCH net-next v2] net: core: change bool members of struct net

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Message-ID: <f8bbbd11-0ad2-77e6-c4fe-e3f643e7e243@gmail.com>
Date:   Tue, 9 Oct 2018 14:43:27 -0600
From:   David Ahern <dsahern@...il.com>
To:     Heiner Kallweit <hkallweit1@...il.com>,
        David Miller <davem@...emloft.net>
Cc:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        David Laight <David.Laight@...LAB.COM>
Subject: Re: [PATCH net-next v2] net: core: change bool members of struct
 net_device to bitfield members

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).