netdev - Re: 答复: [PATCH][v2] page_pool: handle page recycle for NUMA_NO

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Date:   Mon, 16 Dec 2019 12:16:30 +0200
From:   Ilias Apalodimas <ilias.apalodimas@...aro.org>
To:     "Li,Rongqing" <lirongqing@...du.com>
Cc:     Yunsheng Lin <linyunsheng@...wei.com>,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        Saeed Mahameed <saeedm@...lanox.com>,
        "jonathan.lemon@...il.com" <jonathan.lemon@...il.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "mhocko@...nel.org" <mhocko@...nel.org>,
        "peterz@...radead.org" <peterz@...radead.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "bhelgaas@...gle.com" <bhelgaas@...gle.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Björn Töpel <bjorn.topel@...el.com>
Subject: Re: 答复: [PATCH][v2] page_pool:
 handle page recycle for NUMA_NO_NODE condition

> > > 
> > > Simply clearing the pool->alloc.cache when calling page_pool_update_nid()
> > > seems better.
> > > 
> > 
> > How about the below codes, the driver can configure p.nid to any, which will be adjusted in NAPI polling, irq migration will not be problem, but it will add a check into hot path.
> 
> We'll have to check the impact on some high speed (i.e 100gbit) interface
> between doing anything like that. Saeed's current patch runs once per NAPI. This
> runs once per packet. The load might be measurable. 
> The READ_ONCE is needed in case all producers/consumers run on the same CPU

I meant different cpus!

> right?
> 
> 
> Thanks
> /Ilias
> > 
> > diff --git a/net/core/page_pool.c b/net/core/page_pool.c
> > index a6aefe989043..4374a6239d17 100644
> > --- a/net/core/page_pool.c
> > +++ b/net/core/page_pool.c
> > @@ -108,6 +108,10 @@ static struct page *__page_pool_get_cached(struct page_pool *pool)
> >                 if (likely(pool->alloc.count)) {
> >                         /* Fast-path */
> >                         page = pool->alloc.cache[--pool->alloc.count];
> > +
> > +                       if (unlikely(READ_ONCE(pool->p.nid) != numa_mem_id()))
> > +                               WRITE_ONCE(pool->p.nid, numa_mem_id());
> > +
> >                         return page;
> >                 }
> >                 refill = true;
> > @@ -155,6 +159,10 @@ static struct page *__page_pool_alloc_pages_slow(struct page_pool *pool,
> >         if (pool->p.order)
> >                 gfp |= __GFP_COMP;
> >  
> > +
> > +       if (unlikely(READ_ONCE(pool->p.nid) != numa_mem_id()))
> > +               WRITE_ONCE(pool->p.nid, numa_mem_id());
> > +
> >         /* FUTURE development:
> >          *
> >          * Current slow-path essentially falls back to single page
> > Thanks
> > 
> > -Li
> > > >
> >