On Tue, May 16, 2017 at 5:00 PM, Eric Dumazet <eduma...@google.com> wrote: > We abuse tcp_time_stamp for two different cases : > > 1) base to generate TCP Timestamp options (RFC 7323) > > 2) A 32bit version of jiffies since some TCP fields > are 32bit wide to save memory. > > Since we want in the future to have 1ms TCP TS clock, > regardless of HZ value, we want to cleanup things. > > tcp_jiffies32 is the truncated jiffies value, > which will be used only in places where we want a 'host' > timestamp. > > Signed-off-by: Eric Dumazet <eduma...@google.com>
Acked-by: Soheil Hassas Yeganeh <soh...@google.com> > --- > include/net/tcp.h | 13 ++++++++----- > 1 file changed, 8 insertions(+), 5 deletions(-) > > diff --git a/include/net/tcp.h b/include/net/tcp.h > index > b4dc93dae98c2d175ccadce150083705d237555e..4b45be5708215bae4551a5430b63ab2777baf447 > 100644 > --- a/include/net/tcp.h > +++ b/include/net/tcp.h > @@ -700,11 +700,14 @@ u32 __tcp_select_window(struct sock *sk); > > void tcp_send_window_probe(struct sock *sk); > > -/* TCP timestamps are only 32-bits, this causes a slight > - * complication on 64-bit systems since we store a snapshot > - * of jiffies in the buffer control blocks below. We decided > - * to use only the low 32-bits of jiffies and hide the ugly > - * casts with the following macro. > +/* TCP uses 32bit jiffies to save some space. > + * Note that this is different from tcp_time_stamp, which > + * historically has been the same until linux-4.13. > + */ > +#define tcp_jiffies32 ((u32)jiffies) > + > +/* Generator for TCP TS option (RFC 7323) > + * Currently tied to 'jiffies' but will soon be driven by 1 ms clock. > */ > #define tcp_time_stamp ((__u32)(jiffies)) > > -- > 2.13.0.303.g4ebf302169-goog >
