Subject: Re: [PATCH] IPVS: Modify the SH scheduler to use weights

From: Simon Horman <[email-masked]>
Date: Thu, 8 Dec 2011 09:37:04 +0900

On Wed, Dec 07, 2011 at 12:30:38PM +0100, Pablo Neira Ayuso wrote:
> On Wed, Dec 07, 2011 at 05:07:03PM +0900, Simon Horman wrote:
> > From: Michael Maxim <[email-masked]>
> > 
> > Modify the algorithm to build the source hashing hash table to add
> > extra slots for destinations with higher weight. This has the effect
> > of allowing an IPVS SH user to give more connections to hosts that
> > have been configured to have a higher weight.
> > 
> > Signed-off-by: Michael Maxim <[email-masked]>
> > Signed-off-by: Simon Horman <[email-masked]>
> > ---
> >  net/netfilter/ipvs/Kconfig    |   15 +++++++++++++++
> >  net/netfilter/ipvs/ip_vs_sh.c |   20 ++++++++++++++++++--
> >  2 files changed, 33 insertions(+), 2 deletions(-)
> > 
> > diff --git a/net/netfilter/ipvs/Kconfig b/net/netfilter/ipvs/Kconfig
> > index 70bd1d0..af4c0b8 100644
> > --- a/net/netfilter/ipvs/Kconfig
> > +++ b/net/netfilter/ipvs/Kconfig
> > @@ -232,6 +232,21 @@ config	IP_VS_NQ
> >  	  If you want to compile it in kernel, say Y. To compile it as a
> >  	  module, choose M here. If unsure, say N.
> >  
> > +comment 'IPVS SH scheduler'
> > +
> > +config IP_VS_SH_TAB_BITS
> > +	int "IPVS source hashing table size (the Nth power of 2)"
> > +	range 4 20
> > +	default 8
> > +	---help---
> > +	  The source hashing scheduler maps source IPs to destinations
> > +	  stored in a hash table. This table is tiled by each destination
> > +	  until all slots in the table are filled. When using weights to
> > +	  allow destinations to receive more connections, the table is
> > +	  tiled an amount proportional to the weights specified. The table
> > +	  needs to be large enough to effectively fit all the destinations
> > +	  multiplied by their respective weights.
> 
> Hm, does this really belong to this patch?

It seemed reasonable to me, as it is related to the main purpose of
the patch. But I'm happy to split it out into a separate patch.

> 
> > +
> >  comment 'IPVS application helper'
> >  
> >  config	IP_VS_FTP
> > diff --git a/net/netfilter/ipvs/ip_vs_sh.c b/net/netfilter/ipvs/ip_vs_sh.c
> > index 33815f4..e0ca520 100644
> > --- a/net/netfilter/ipvs/ip_vs_sh.c
> > +++ b/net/netfilter/ipvs/ip_vs_sh.c
> > @@ -30,6 +30,11 @@
> >   * server is dead or overloaded, the load balancer can bypass the cache
> >   * server and send requests to the original server directly.
> >   *
> > + * The weight destination attribute can be used to control the
> > + * distribution of connections to the destinations in servernode. The
> > + * greater the weight, the more connections the destination
> > + * will receive.
> > + *
> >   */
> >  
> >  #define KMSG_COMPONENT "IPVS"
> > @@ -99,9 +104,11 @@ ip_vs_sh_assign(struct ip_vs_sh_bucket *tbl, struct ip_vs_service *svc)
> >  	struct ip_vs_sh_bucket *b;
> >  	struct list_head *p;
> >  	struct ip_vs_dest *dest;
> > +	int d_count;
> >  
> >  	b = tbl;
> >  	p = &svc->destinations;
> > +	d_count = 0;
> >  	for (i=0; i<IP_VS_SH_TAB_SIZE; i++) {
> >  		if (list_empty(p)) {
> >  			b->dest = NULL;
> > @@ -113,14 +120,23 @@ ip_vs_sh_assign(struct ip_vs_sh_bucket *tbl, struct ip_vs_service *svc)
> >  			atomic_inc(&dest->refcnt);
> >  			b->dest = dest;
> >  
> > -			p = p->next;
> > +			IP_VS_DBG_BUF(6, "assigned i: %d dest: %s weight: %d\n",
> > +				      i, IP_VS_DBG_ADDR(svc->af, &dest->addr),
> > +				      atomic_read(&dest->weight));
> > +
> > +			/* Don't move to next dest until filling weight */
> > +			if (++d_count >= atomic_read(&dest->weight)) {
> > +				p = p->next;
> > +				d_count = 0;
> > +			}
> > +
> >  		}
> >  		b++;
> >  	}
> > +
> >  	return 0;
> >  }
> >  
> > -
> 
> While at it, would you remove this unnecessary deletions/additions.

Sure.