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

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Date:   Mon, 16 Dec 2019 09:51:29 +0800
From:   Yunsheng Lin <linyunsheng@...wei.com>
To:     Jesper Dangaard Brouer <brouer@...hat.com>
CC:     "Li,Rongqing" <lirongqing@...du.com>,
        Saeed Mahameed <saeedm@...lanox.com>,
        "ilias.apalodimas@...aro.org" <ilias.apalodimas@...aro.org>,
        "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: [PATCH][v2] page_pool: handle page recycle for NUMA_NO_NODE
 condition

On 2019/12/13 16:48, Jesper Dangaard Brouer wrote:> You are basically saying that the NUMA check should be moved to
> allocation time, as it is running the RX-CPU (NAPI).  And eventually
> after some time the pages will come from correct NUMA node.
> 
> I think we can do that, and only affect the semi-fast-path.
> We just need to handle that pages in the ptr_ring that are recycled can
> be from the wrong NUMA node.  In __page_pool_get_cached() when
> consuming pages from the ptr_ring (__ptr_ring_consume_batched), then we
> can evict pages from wrong NUMA node.

Yes, that's workable.

> 
> For the pool->alloc.cache we either accept, that it will eventually
> after some time be emptied (it is only in a 100% XDP_DROP workload that
> it will continue to reuse same pages).   Or we simply clear the
> pool->alloc.cache when calling page_pool_update_nid().

Simply clearing the pool->alloc.cache when calling page_pool_update_nid()
seems better.

>