From mboxrd@z Thu Jan  1 00:00:00 1970
From: Eric Dumazet <eric.dumazet@gmail.com>
Date: Tue, 06 Mar 2018 18:53:29 -0800
Subject: [Intel-wired-lan] [RFC v3 net-next 08/18] net: SO_TXTIME: Add
 clockid and drop_if_late params
In-Reply-To: <20180307011230.24001-9-jesus.sanchez-palencia@intel.com>
References: <20180307011230.24001-1-jesus.sanchez-palencia@intel.com>
 <20180307011230.24001-9-jesus.sanchez-palencia@intel.com>
Message-ID: <1520391209.109662.33.camel@gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: 7bit
To: intel-wired-lan@osuosl.org
List-ID: <intel-wired-lan.osuosl.org>

On Tue, 2018-03-06 at 17:12 -0800, Jesus Sanchez-Palencia wrote:
> Extend SO_TXTIME APIs with new per-packet parameters: a clockid_t and
> a drop_if_late flag. With this commit the API becomes:
> 
> 

 * diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
 * index d8340e6e8814..951969ceaf65 100644
 * --- a/include/linux/skbuff.h
 * +++ b/include/linux/skbuff.h
 * @@ -788,6 +788,9 @@ struct sk_buff {
 * ?	__u8			tc_redirected:1;
 * ?	__u8			tc_from_ingress:1;
 * ?#endif
 * +	__u8			tc_drop_if_late:1;
 * +
 * +	clockid_t		txtime_clockid;
 * ?
 * ?#ifdef CONFIG_NET_SCHED
 * ?	__u16			tc_index;	/* traffic
   control index */


This is adding 32+1 bits to sk_buff, and possibly holes in this very
very hot (and already too fat) structure.

Do we really need 32 bits for a clockid_t ?