linux-kernel - Re: [PATCH 2/3] IPVS: add wlib & wlip schedulers

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Message-ID: <alpine.LFD.2.11.1501222250220.2572@ja.home.ssi.bg>
Date:	Thu, 22 Jan 2015 23:07:48 +0200 (EET)
From:	Julian Anastasov <ja@....bg>
To:	Chris Caputo <ccaputo@....net>
cc:	Wensong Zhang <wensong@...ux-vs.org>,
	Simon Horman <horms@...ge.net.au>, lvs-devel@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] IPVS: add wlib & wlip schedulers


	Hello,

On Tue, 20 Jan 2015, Chris Caputo wrote:

> On Tue, 20 Jan 2015, Julian Anastasov wrote:
> > > +                      (u64)dr * (u64)lwgt < (u64)lr * (u64)dwgt ||
> [...]
> > > +  	                   (dr == lr && dwgt > lwgt)) {
> > 
> > 	Above check is redundant.
> 
> I accepted your feedback and applied it to the below, except for this 
> item.  I believe if dr and lr are zero (no traffic), we still want to 
> choose the higher weight, thus a separate comparison is needed.

	ok

> +	spin_lock_bh(&svc->sched_lock);
> +	p = (struct list_head *)svc->sched_data;
> +	last = dest = list_entry(p, struct ip_vs_dest, n_list);
> +
> +	do {
> +		list_for_each_entry_continue_rcu(dest,
> +						 &svc->destinations,
> +						 n_list) {
> +			dwgt = (u32)atomic_read(&dest->weight);
> +			if (!(dest->flags & IP_VS_DEST_F_OVERLOAD) &&
> +			    dwgt > 0) {
> +                               spin_lock(&dest->stats.lock);

	May be there is a way to avoid this spin_lock
by using u64_stats_fetch_begin and corresponding
u64_stats_update_begin in estimation_timer(). We can
even remove this ->lock, it will be replaced by ->syncp.
The benefit is for 64-bit platforms where we avoid
lock here in the scheduler. Otherwise, I don't see
other implementation problems in this patch and I'll
check it more carefully this weekend.

Regards

--
Julian Anastasov <ja@....bg>
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