From: David Laight <David.Laight@ACULAB.COM>
To: 'Eric Dumazet' <edumazet@google.com>
Cc: Stephen Hemminger <stephen@networkplumber.org>,
Arjun Roy <arjunroy.kdev@gmail.com>,
"davem@davemloft.net" <davem@davemloft.net>,
"netdev@vger.kernel.org" <netdev@vger.kernel.org>,
"arjunroy@google.com" <arjunroy@google.com>,
"soheil@google.com" <soheil@google.com>
Subject: RE: [net-next v2 1/8] net-zerocopy: Copy straggler unaligned data for TCP Rx. zerocopy.
Date: Fri, 4 Dec 2020 09:02:40 +0000 [thread overview]
Message-ID: <1aabb09d81d24480ab2cf99e30138a3e@AcuMS.aculab.com> (raw)
In-Reply-To: <CANn89iKfUdRygt_k2Axf1MZ2FzkOQ9R6S2oJAvKuLqRp-wZvsQ@mail.gmail.com>
From: Eric
> Sent: 03 December 2020 23:15
>
> On Fri, Dec 4, 2020 at 12:01 AM David Laight <David.Laight@aculab.com> wrote:
> >
> > From: Stephen Hemminger
> > > Sent: 03 December 2020 00:15
> > >
> > > On Wed, 2 Dec 2020 14:09:38 -0800
> > > Arjun Roy <arjunroy.kdev@gmail.com> wrote:
> > >
> > > > diff --git a/include/uapi/linux/tcp.h b/include/uapi/linux/tcp.h
> > > > index cfcb10b75483..62db78b9c1a0 100644
> > > > --- a/include/uapi/linux/tcp.h
> > > > +++ b/include/uapi/linux/tcp.h
> > > > @@ -349,5 +349,7 @@ struct tcp_zerocopy_receive {
> > > > __u32 recv_skip_hint; /* out: amount of bytes to skip */
> > > > __u32 inq; /* out: amount of bytes in read queue */
> > > > __s32 err; /* out: socket error */
> > > > + __u64 copybuf_address; /* in: copybuf address (small reads) */
> > > > + __s32 copybuf_len; /* in/out: copybuf bytes avail/used or error */
> >
> > You need to swap the order of the above fields to avoid padding
> > and differing alignments for 32bit and 64bit apps.
>
> I do not think so. Please review this patch series carefully.
Late at night.
The actual problem is 'tail padding'.
David
-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)
next prev parent reply other threads:[~2020-12-04 9:04 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-02 22:09 [net-next v2 0/8] Perf. optimizations for TCP Recv. Zerocopy Arjun Roy
2020-12-02 22:09 ` [net-next v2 1/8] net-zerocopy: Copy straggler unaligned data for TCP Rx. zerocopy Arjun Roy
2020-12-03 0:15 ` Stephen Hemminger
2020-12-03 0:24 ` Arjun Roy
2020-12-03 23:01 ` David Laight
2020-12-03 23:14 ` Eric Dumazet
2020-12-04 9:02 ` David Laight [this message]
2020-12-03 23:19 ` Arjun Roy
2020-12-03 23:24 ` Arjun Roy
2020-12-04 9:03 ` David Laight
2020-12-04 22:37 ` Arjun Roy
2020-12-02 22:09 ` [net-next v2 2/8] net-tcp: Introduce tcp_recvmsg_locked() Arjun Roy
2020-12-02 22:09 ` [net-next v2 3/8] net-zerocopy: Refactor skb frag fast-forward op Arjun Roy
2020-12-02 22:09 ` [net-next v2 4/8] net-zerocopy: Refactor frag-is-remappable test Arjun Roy
2020-12-02 22:09 ` [net-next v2 5/8] net-zerocopy: Fast return if inq < PAGE_SIZE Arjun Roy
2020-12-02 22:09 ` [net-next v2 6/8] net-zerocopy: Introduce short-circuit small reads Arjun Roy
2020-12-02 22:09 ` [net-next v2 7/8] net-zerocopy: Set zerocopy hint when data is copied Arjun Roy
2020-12-02 22:09 ` [net-next v2 8/8] net-zerocopy: Defer vm zap unless actually needed Arjun Roy
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