netdev - Re: [PATCH] snmp: add missing counters for RFC 4293

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Message-ID: <20090423165620.GB30405@hmsreliant.think-freely.org>
Date:	Thu, 23 Apr 2009 12:56:20 -0400
From:	Neil Horman <nhorman@...driver.com>
To:	Eric Dumazet <dada1@...mosbay.com>
Cc:	David Miller <davem@...emloft.net>, netdev@...r.kernel.org
Subject: Re: [PATCH] snmp: add missing counters for RFC 4293

On Thu, Apr 23, 2009 at 06:37:07PM +0200, Eric Dumazet wrote:
> Neil Horman a écrit :
> > On Wed, Apr 22, 2009 at 07:39:55PM +0200, Eric Dumazet wrote:
> >> <previous contents snipped>
> >>
> > 
> > 
> > ok, new patch, functionally equivalent, with the following enhancements:
> > 
> > 1) Replaces INRECEIVES/OUTREQUESTS with INPKTS/OUTPKTS.  I did this
> >    so that I could use the dual count update in (2) for INPKTS/INOCTETS
> >    and OUTPKTS/OUTOCTETS
> > 2) Added dual stat update routines for IP/IP6, named *_UPD_PO_STATS[_BH]
> >    which updates a pair of stats, a P(acket) count, and an (O)ctet count
> > 3) Added BCASTPKS/BCASTOCTETS for completeness
> > 
> > 
> > 
> > The IP MIB (RFC 4293) defines stats for InOctets, OutOctets, InMcastOctets and
> > OutMcastOctets:
> > http://tools.ietf.org/html/rfc4293
> > But it seems we don't track those in any way that easy to separate from other
> > protocols.  This patch adds those missing counters to the stats file. Tested
> > successfully by me
> > 
> > Signed-off-by: Neil Horman <nhorman@...driver.com>
> > 
> 
> 
> 
> > +#define SNMP_UPD_PO_STATS(mib, basefield, addend)	\
> > +	do { \
> > +		int __cpu = get_cpu(); \
> > +		per_cpu_ptr(mib[!in_softirq()], __cpu)->mibs[basefield##PKTS]++; \
> > +		per_cpu_ptr(mib[!in_softirq()], __cpu)->mibs[basefield##OCTETS] += addend;\
> > +		put_cpu(); \
> > +	} while (0)
> 
> Following should be faster, because per_cpu_ptr() and !in_softirq() factorization.
> 
> > +#define SNMP_UPD_PO_STATS(mib, basefield, addend)	\
> > +	do { \
> > +		__typeof__(mib[0]) ptr = per_cpu_ptr(mib[!in_softirq()], get_cpu()); \
> > +		ptr->mibs[basefield##PKTS]++; \
> > +		ptr->mibs[basefield##OCTETS] += addend;\
> > +		put_cpu(); \
> > +	} while (0)
> 
> BTW, we miss HC (64bits) values on 32bit arches, and some RFC (not 4293, but in 4113) mention they
>  should be provided if counters can be updated more than 1 million times per second.
> 
> And for Octets counters, this is definitly the case with 100 Mbit networks... Oh well
Yeah, I was wondering about this.  Think it would be worthwhile to export all of
these counters as 64 bit, rather than 32 bit?  Userspace can then have the HC
counters, and downcast to the standard 32 bit flavors.  I'd like this patch to
stand as it is, but I think that might be a good subsequent change to make

Neil

> 
> 
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