linux-kernel - Re: [PATCH net-next v8 2/6] page_pool: unify frag_count handling in page_pool_is_last

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Message-ID: <e7f2d1b1-49fe-cf8d-eb96-c5ddf52903a0@huawei.com>
Date:   Mon, 18 Sep 2023 19:15:15 +0800
From:   Yunsheng Lin <linyunsheng@...wei.com>
To:     Paolo Abeni <pabeni@...hat.com>, <davem@...emloft.net>,
        <kuba@...nel.org>
CC:     <netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        Lorenzo Bianconi <lorenzo@...nel.org>,
        Alexander Duyck <alexander.duyck@...il.com>,
        Liang Chen <liangchen.linux@...il.com>,
        Alexander Lobakin <aleksander.lobakin@...el.com>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        Ilias Apalodimas <ilias.apalodimas@...aro.org>,
        Eric Dumazet <edumazet@...gle.com>
Subject: Re: [PATCH net-next v8 2/6] page_pool: unify frag_count handling in
 page_pool_is_last_frag()

On 2023/9/14 23:17, Paolo Abeni wrote:
>> --- a/net/core/page_pool.c
>> +++ b/net/core/page_pool.c
>> @@ -376,6 +376,14 @@ static void page_pool_set_pp_info(struct page_pool *pool,
>>  {
>>  	page->pp = pool;
>>  	page->pp_magic |= PP_SIGNATURE;
>> +
>> +	/* Ensuring all pages have been split into one big frag initially:
>> +	 * page_pool_set_pp_info() is only called once for every page when it
>> +	 * is allocated from the page allocator and page_pool_fragment_page()
>> +	 * is dirtying the same cache line as the page->pp_magic above, so
>> +	 * the overhead is negligible.
>> +	 */
>> +	page_pool_fragment_page(page, 1);
>>  	if (pool->p.init_callback)
>>  		pool->p.init_callback(page, pool->p.init_arg);
>>  }
> 
> I think it would be nice backing the above claim with some benchmarks.
> (possibly even just a micro-benchmark around the relevant APIs)
> and include such info into the changelog message.

Sure, will adjust Jesper's below micro-benchmark to test it:
https://github.com/netoptimizer/prototype-kernel/blob/master/kernel/lib/bench_page_pool_simple.c

Please let me know if there is other better idea to do the
micro-benchmark in your mind, thanks.

> 
> Cheers,
> 
> Paolo
> 
> .
>