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

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Date:   Sun, 18 Dec 2022 10:20:30 +0900
From:   Masami Hiramatsu (Google) <mhiramat@...nel.org>
To:     Wenchao Hao <haowenchao@...wei.com>
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 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,

> 
> 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
> 


-- 
Masami Hiramatsu (Google) <mhiramat@...nel.org>