linux-kernel - Re: [PATCH V2 2/7] mm/gup: add gup trace points

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Message-ID: <565F8092.7000001@intel.com>
Date:	Wed, 2 Dec 2015 15:36:50 -0800
From:	Dave Hansen <dave.hansen@...el.com>
To:	Yang Shi <yang.shi@...aro.org>, akpm@...ux-foundation.org,
	rostedt@...dmis.org, mingo@...hat.com
Cc:	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	linaro-kernel@...ts.linaro.org
Subject: Re: [PATCH V2 2/7] mm/gup: add gup trace points

On 12/02/2015 02:53 PM, Yang Shi wrote:
> diff --git a/mm/gup.c b/mm/gup.c
> index deafa2c..10245a4 100644
> --- a/mm/gup.c
> +++ b/mm/gup.c
> @@ -13,6 +13,9 @@
>  #include <linux/rwsem.h>
>  #include <linux/hugetlb.h>
>  
> +#define CREATE_TRACE_POINTS
> +#include <trace/events/gup.h>
> +
>  #include <asm/pgtable.h>
>  #include <asm/tlbflush.h>

This needs to be _the_ last thing that gets #included.  Otherwise, you
risk colliding with any other trace header that gets implicitly included
below.

> @@ -1340,6 +1346,8 @@ int __get_user_pages_fast(unsigned long start, int nr_pages, int write,
>  					start, len)))
>  		return 0;
>  
> +	trace_gup_get_user_pages_fast(start, nr_pages, write, pages);
> +
>  	/*
>  	 * Disable interrupts.  We use the nested form as we can already have
>  	 * interrupts disabled by get_futex_key.

It would be _really_ nice to be able to see return values from the
various gup calls as well.  Is that feasible?
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