Date: Mon, 14 Jan 2002 08:05:49 +0100 (CET) From: Michal Mertl <mime@traveller.cz> To: Terry Lambert <tlambert2@mindspring.com> Cc: arch@FreeBSD.ORG Subject: Re: 64 bit counters again Message-ID: <Pine.BSF.4.41.0201140750390.82342-100000@prg.traveller.cz> In-Reply-To: <3C41F3FD.4ECC8CD@mindspring.com>
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On Sun, 13 Jan 2002, Terry Lambert wrote: > Michal Mertl wrote: > > But anyway I continued on some work on STABLE (but believe lot of my work > > could be used on CURRENT after some modification) and get kernel and world > > building with 64 bit counters on network interfaces (struct if_data) > > and in protocols (struct ipstat, tcpstat, udpstat, icmpstat, igmpstat). > > Not to discount the value of this work, but... > > 1) It makes counting slower on 32 bit processors. How much slower? 64 bit addition on i386 is only 2 simple instructions instead of 1 for 32 bit. > > 2) The values are not accessible from SNMP, which is > limited to 32 bit counters. > Not true. You do better check things before explaining them to anyone. > 3) While you could export these values as strings and > not numbers over SNMP, doing this would mean you > would need to use a MIB which was not a superset > of an RFC'ed MIB. As stated before there is 64bit counter type in SNMP. On cisco I use it every other day. > So it seems to me that the utility of this on 32 bit machines > is incredibly limited (e.g. shell programs). > I don't see that much utility either, only to have right values. But I got at least one email asking for the patch because the guy uses the counters. He said they overflow in several minutes for him so are really useless. > PS: FWIW, I agree that these things should be 64 bits on > 64 bit architectures, even if they can only export > the low 32 bits for SNMP. > I think some counters are already 64 bit on 64 bit architectures, because they are defined as u_long which is (I believe) 64 bit. The most importatnt thing is that I don't believe the operations are expensive (when not using locked atomic ops at least). -- Michal Mertl mime@traveller.cz To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-arch" in the body of the message
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