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

To: Chris Caputo <ccaputo@xxxxxxx>
Subject: Re: [PATCH 2/3] IPVS: add wlib & wlip schedulers
Cc: Wensong Zhang <wensong@xxxxxxxxxxxx>, Simon Horman <horms@xxxxxxxxxxxx>, lvs-devel@xxxxxxxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx
From: Julian Anastasov <ja@xxxxxx>
Date: Thu, 22 Jan 2015 23:07:48 +0200 (EET)
        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@xxxxxx>
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