linux-kernel - Re: [PATCH] cma:tracing: Print alloc result in trace_cma_alloc

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Date:   Wed, 28 Dec 2022 16:17:32 +0800
From:   Wenchao Hao <haowenchao@...wei.com>
To:     "Masami Hiramatsu (Google)" <mhiramat@...nel.org>
CC:     Steven Rostedt <rostedt@...dmis.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        <linux-kernel@...r.kernel.org>, <linux-mm@...ck.org>,
        <liuzhiqiang26@...wei.com>, <linfeilong@...wei.com>
Subject: Re: [PATCH] cma:tracing: Print alloc result in trace_cma_alloc_finish

On 2022/12/18 9:20, Masami Hiramatsu (Google) wrote:
> On Thu, 8 Dec 2022 22:21:30 +0800
> Wenchao Hao <haowenchao@...wei.com> wrote:
> 
>> The result of allocation is not printed in trace_cma_alloc_finish
>> now, while it's important to do it so we can set filters to catch
>> specific error on allocation or trigger some operations on specific
>> error.
>>
>> Although we have printed the result in log, but the log is
>> conditional and could not be filtered by tracing event.
>>
>> What's more, it introduce little overhead to print this result.
>> The result of allocation is named as errorno in trace.
> 
> This looks good to me. BTW, with this change, cma_alloc_class has only
> one event - cma_alloc_busy_retry. If so, can we remove the cma_alloc_class?
> 
> Thank you,
> 

Sorry, I got COVID-19 and just recovered, so did not response your email in time.

The cma_alloc_class should be removed. Since Andrew has applied this patch,
I would send another one to remove it.

>>
>> Signed-off-by: Wenchao Hao <haowenchao@...wei.com>
>> ---
>>  include/trace/events/cma.h | 32 +++++++++++++++++++++++++++++---
>>  mm/cma.c                   |  2 +-
>>  2 files changed, 30 insertions(+), 4 deletions(-)
>>
>> diff --git a/include/trace/events/cma.h b/include/trace/events/cma.h
>> index 3d708dae1542..ef75ea606ab2 100644
>> --- a/include/trace/events/cma.h
>> +++ b/include/trace/events/cma.h
>> @@ -91,12 +91,38 @@ TRACE_EVENT(cma_alloc_start,
>>  		  __entry->align)
>>  );
>>  
>> -DEFINE_EVENT(cma_alloc_class, cma_alloc_finish,
>> +TRACE_EVENT(cma_alloc_finish,
>>  
>>  	TP_PROTO(const char *name, unsigned long pfn, const struct page *page,
>> -		 unsigned long count, unsigned int align),
>> +		 unsigned long count, unsigned int align, int errorno),
>>  
>> -	TP_ARGS(name, pfn, page, count, align)
>> +	TP_ARGS(name, pfn, page, count, align, errorno),
>> +
>> +	TP_STRUCT__entry(
>> +		__string(name, name)
>> +		__field(unsigned long, pfn)
>> +		__field(const struct page *, page)
>> +		__field(unsigned long, count)
>> +		__field(unsigned int, align)
>> +		__field(int, errorno)
>> +	),
>> +
>> +	TP_fast_assign(
>> +		__assign_str(name, name);
>> +		__entry->pfn = pfn;
>> +		__entry->page = page;
>> +		__entry->count = count;
>> +		__entry->align = align;
>> +		__entry->errorno = errorno;
>> +	),
>> +
>> +	TP_printk("name=%s pfn=0x%lx page=%p count=%lu align=%u errorno=%d",
>> +		  __get_str(name),
>> +		  __entry->pfn,
>> +		  __entry->page,
>> +		  __entry->count,
>> +		  __entry->align,
>> +		  __entry->errorno)
>>  );
>>  
>>  DEFINE_EVENT(cma_alloc_class, cma_alloc_busy_retry,
>> diff --git a/mm/cma.c b/mm/cma.c
>> index 4a978e09547a..a75b17b03b66 100644
>> --- a/mm/cma.c
>> +++ b/mm/cma.c
>> @@ -491,7 +491,7 @@ struct page *cma_alloc(struct cma *cma, unsigned long count,
>>  		start = bitmap_no + mask + 1;
>>  	}
>>  
>> -	trace_cma_alloc_finish(cma->name, pfn, page, count, align);
>> +	trace_cma_alloc_finish(cma->name, pfn, page, count, align, ret);
>>  
>>  	/*
>>  	 * CMA can allocate multiple page blocks, which results in different
>> -- 
>> 2.32.0
>>
> 
>