Re: [PATCH v2 07/12] icmp: Simplify socket expiry scanning

[David Gibson <david@gibson.dropbear.id.au>]

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On Sat, Jan 06, 2024 at 04:59:53PM +0100, Stefano Brivio wrote:
> On Thu, 21 Dec 2023 17:53:22 +1100
> David Gibson <david@gibson.dropbear.id.au> wrote:
> 
> > Currently we use icmp_act[] to scan for ICMP ids which might have an open
> > socket which could time out.  However icmp_act[] contains no information
> > that's not already in icmp_id_map[] - it's just an "index" which allows
> > scanning for relevant entries with less cache footprint.
> > 
> > We only scan for ICMP socket expiry every 1s, though, so it's not clear
> > that cache footprint really matters.  Furthermore, there's no strong reason
> > we need to scan even that often - the timeout is fairly arbitrary and
> > approximate.
> > 
> > So, eliminate icmp_act[] in favour of directly scanning icmp_id_map[] and
> > compensate for the cache impact by reducing the scan frequency to once
> > every 10s.
> > 
> > Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
> > ---
> >  icmp.c | 34 ++++++----------------------------
> >  icmp.h |  2 +-
> >  2 files changed, 7 insertions(+), 29 deletions(-)
> > 
> > diff --git a/icmp.c b/icmp.c
> > index dd98c7f..02739b9 100644
> > --- a/icmp.c
> > +++ b/icmp.c
> > @@ -56,9 +56,6 @@ struct icmp_id_sock {
> >  /* Indexed by ICMP echo identifier */
> >  static struct icmp_id_sock icmp_id_map[IP_VERSIONS][ICMP_NUM_IDS];
> >  
> > -/* Bitmaps, activity monitoring needed for identifier */
> > -static uint8_t icmp_act[IP_VERSIONS][DIV_ROUND_UP(ICMP_NUM_IDS, 8)];
> > -
> >  /**
> >   * icmp_sock_handler() - Handle new data from IPv4 ICMP socket
> >   * @c:		Execution context
> > @@ -194,7 +191,6 @@ int icmp_tap_handler(const struct ctx *c, uint8_t pif, int af,
> >  			debug("ICMP: new socket %i for echo ID %i", s, id);
> >  		}
> >  		icmp_id_map[V4][id].ts = now->tv_sec;
> > -		bitmap_set(icmp_act[V4], id);
> >  
> >  		sa.sin_addr = *(struct in_addr *)daddr;
> >  		if (sendto(s, ih, sizeof(*ih) + plen, MSG_NOSIGNAL,
> > @@ -237,7 +233,6 @@ int icmp_tap_handler(const struct ctx *c, uint8_t pif, int af,
> >  			debug("ICMPv6: new socket %i for echo ID %i", s, id);
> >  		}
> >  		icmp_id_map[V6][id].ts = now->tv_sec;
> > -		bitmap_set(icmp_act[V6], id);
> >  
> >  		sa.sin6_addr = *(struct in6_addr *)daddr;
> >  		if (sendto(s, ih, sizeof(*ih) + plen, MSG_NOSIGNAL,
> > @@ -261,20 +256,15 @@ fail_sock:
> >  /**
> >   * icmp_timer_one() - Handler for timed events related to a given identifier
> >   * @c:		Execution context
> > - * @v6:		Set for IPv6 echo identifier bindings
> > - * @id:		Echo identifier, host order
> > + * @id_map:	id socket information to check timers for
> 
> It took me a few readings to understand this... what about:
> 
>  * @id_sock:	Socket number and activity timestamp
> 
> ?

Works for me.  Updated.

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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