netdev - Re: [PATCH net-next v2] net-timestamp: namespacify the sysctl_tstamp_allow

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Message-ID: <CAL+tcoA6YCkYvFJkpbmSuT=MVn_81KmJQyMYtojKC5kBFZvqfw@mail.gmail.com>
Date: Wed, 2 Oct 2024 19:26:32 +0900
From: Jason Xing <kerneljasonxing@...il.com>
To: Eric Dumazet <edumazet@...gle.com>
Cc: davem@...emloft.net, kuba@...nel.org, pabeni@...hat.com, 
	willemdebruijn.kernel@...il.com, willemb@...gle.com, netdev@...r.kernel.org, 
	Jason Xing <kernelxing@...cent.com>
Subject: Re: [PATCH net-next v2] net-timestamp: namespacify the sysctl_tstamp_allow_data

Hello Eric,

On Wed, Oct 2, 2024 at 4:41 PM Eric Dumazet <edumazet@...gle.com> wrote:
>
> On Wed, Oct 2, 2024 at 6:18 AM Jason Xing <kerneljasonxing@...il.com> wrote:
> >
> > From: Jason Xing <kernelxing@...cent.com>
> >
> > Let it be tuned in per netns by admins.
> >
> > Signed-off-by: Jason Xing <kernelxing@...cent.com>
> > ---
> > v2
> > Link: https://lore.kernel.org/all/66fa81b2ddf10_17948d294bb@willemb.c.googlers.com.notmuch/
> > 1. remove the static global from sock.c
> > 2. reorder the tests
> > 3. I removed the patch [1/3] because I made one mistake
> > 4. I also removed the patch [2/3] because Willem soon will propose a
> > packetdrill test that is better.
> > Now, I only need to write this standalone patch.
> > ---
> >  include/net/netns/core.h   |  1 +
> >  include/net/sock.h         |  2 --
> >  net/core/net_namespace.c   |  1 +
> >  net/core/skbuff.c          |  2 +-
> >  net/core/sock.c            |  2 --
> >  net/core/sysctl_net_core.c | 18 +++++++++---------
> >  6 files changed, 12 insertions(+), 14 deletions(-)
> >
> > diff --git a/include/net/netns/core.h b/include/net/netns/core.h
> > index 78214f1b43a2..ef8b3105c632 100644
> > --- a/include/net/netns/core.h
> > +++ b/include/net/netns/core.h
> > @@ -23,6 +23,7 @@ struct netns_core {
> >  #if IS_ENABLED(CONFIG_RPS) && IS_ENABLED(CONFIG_SYSCTL)
> >         struct cpumask *rps_default_mask;
> >  #endif
> > +       int     sysctl_tstamp_allow_data;
> >  };
>
> This adds another hole for no good reason.
> Please put this after sysctl_txrehash.

Thanks for your reminder.

Before this patch:
struct netns_core {
        struct ctl_table_header *  sysctl_hdr;           /*     0   0x8 */
        int                        sysctl_somaxconn;     /*   0x8   0x4 */
        int                        sysctl_optmem_max;    /*   0xc   0x4 */
        u8                         sysctl_txrehash;      /*  0x10   0x1 */

        /* XXX 7 bytes hole, try to pack */

        struct prot_inuse *        prot_inuse;           /*  0x18   0x8 */
        struct cpumask *           rps_default_mask;     /*  0x20   0x8 */

        /* size: 40, cachelines: 1, members: 6 */
        /* sum members: 33, holes: 1, sum holes: 7 */
        /* last cacheline: 40 bytes */
};

After this patch:
struct netns_core {
        struct ctl_table_header *  sysctl_hdr;           /*     0   0x8 */
        int                        sysctl_somaxconn;     /*   0x8   0x4 */
        int                        sysctl_optmem_max;    /*   0xc   0x4 */
        u8                         sysctl_txrehash;      /*  0x10   0x1 */

        /* XXX 7 bytes hole, try to pack */

        struct prot_inuse *        prot_inuse;           /*  0x18   0x8 */
        struct cpumask *           rps_default_mask;     /*  0x20   0x8 */
        int                        sysctl_tstamp_allow_data; /*  0x28   0x4 */

        /* size: 48, cachelines: 1, members: 7 */
        /* sum members: 37, holes: 1, sum holes: 7 */
        /* padding: 4 */
        /* last cacheline: 48 bytes */
};

See this line "/* sum members: 37, holes: 1, sum holes: 7 */", so I
don't think I introduce a new hole here.

After trying the suggestion you mentioned, the sum holes decreases from 7 to 3:
struct netns_core {
        struct ctl_table_header *  sysctl_hdr;           /*     0   0x8 */
        int                        sysctl_somaxconn;     /*   0x8   0x4 */
        int                        sysctl_optmem_max;    /*   0xc   0x4 */
        u8                         sysctl_txrehash;      /*  0x10   0x1 */

        /* XXX 3 bytes hole, try to pack */

        int                        sysctl_tstamp_allow_data; /*  0x14   0x4 */
        struct prot_inuse *        prot_inuse;           /*  0x18   0x8 */
        struct cpumask *           rps_default_mask;     /*  0x20   0x8 */

        /* size: 40, cachelines: 1, members: 7 */
        /* sum members: 37, holes: 1, sum holes: 3 */
        /* last cacheline: 40 bytes */
};

I will adjust the patch as you said. Thank you, Eric.

Thanks,
Jason