netdev - Re: [PATCH net-next v10 06/14] page

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Date: Fri, 7 Jun 2024 13:31:07 +0100
From: Pavel Begunkov <asml.silence@...il.com>
To: Steven Rostedt <rostedt@...dmis.org>,
 Mina Almasry <almasrymina@...gle.com>
Cc: netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
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 linux-mm@...ck.org, Matthew Wilcox <willy@...radead.org>
Subject: Re: [PATCH net-next v10 06/14] page_pool: convert to use netmem

On 6/6/24 02:48, Steven Rostedt wrote:
> On Thu, 30 May 2024 20:16:05 +0000
> Mina Almasry <almasrymina@...gle.com> wrote:
> 
>> @@ -42,51 +42,52 @@ TRACE_EVENT(page_pool_release,
>>   TRACE_EVENT(page_pool_state_release,
>>   
>>   	TP_PROTO(const struct page_pool *pool,
>> -		 const struct page *page, u32 release),
>> +		 netmem_ref netmem, u32 release),
>>   
>> -	TP_ARGS(pool, page, release),
>> +	TP_ARGS(pool, netmem, release),
>>   
>>   	TP_STRUCT__entry(
>>   		__field(const struct page_pool *,	pool)
>> -		__field(const struct page *,		page)
>> +		__field(netmem_ref,			netmem)
> 
> Why make this of type "netmem_ref" and not just "unsigned long"?
> 
>>   		__field(u32,				release)
>>   		__field(unsigned long,			pfn)
>>   	),
>>   
>>   	TP_fast_assign(
>>   		__entry->pool		= pool;
>> -		__entry->page		= page;
>> +		__entry->netmem		= netmem;
> 
> You could have this be:
> 
> 		__entry->netmem		= (__force unsigned long)netmem;
> 
>>   		__entry->release	= release;
>> -		__entry->pfn		= page_to_pfn(page);
>> +		__entry->pfn		= netmem_to_pfn(netmem);
>>   	),
>>   
>> -	TP_printk("page_pool=%p page=%p pfn=0x%lx release=%u",
>> -		  __entry->pool, __entry->page, __entry->pfn, __entry->release)
>> +	TP_printk("page_pool=%p netmem=%lu pfn=0x%lx release=%u",
>> +		  __entry->pool, (__force unsigned long)__entry->netmem,
> 
> And not have to expose the above text to user space (look at the format
> file it produces).
> 
> It being of type "netmem_ref" in the ring buffer is useless.

netmem is a pointer with one bit serving as a flag, considering
mangling it might be better to %p it and perhaps also print its
type (page* vs iov) separately.

-- 
Pavel Begunkov