linux-kernel - Re: [PATCH] tracing/xen: Hide events that are not used when X86

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Date:   Wed, 11 Oct 2017 19:39:20 -0500
From:   Jeremy Linton <jeremy.linton@....com>
To:     Steven Rostedt <rostedt@...dmis.org>,
        LKML <linux-kernel@...r.kernel.org>
Cc:     Ingo Molnar <mingo@...nel.org>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Juergen Gross <jgross@...e.com>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: Re: [PATCH] tracing/xen: Hide events that are not used when X86_PAE
 is not defined

On 10/10/2017 06:12 PM, Steven Rostedt wrote:
> From: Steven Rostedt (VMware) <rostedt@...dmis.org>
> 
> TRACE_EVENTS() take up memory. If they are defined but not used, then
> they simply waste space. If their use case is behind a define, then the
> trace events should be as well.
> 
> The trace events xen_mmu_set_pte_atomic, xen_mmu_pte_clear, and
> xen_mmu_pmd_clear are not used when CONFIG_X86_PAE is not defined.

The only place i see them being used is mmu_pv.c, where they are wrapped 
in the stated #define.

Looks good.

Reviewed-by: Jeremy Linton <jeremy.linton@....com>

Thanks,

> 
> Signed-off-by: Steven Rostedt (VMware) <rostedt@...dmis.org>
> ---
> Index: linux-trace.git/include/trace/events/xen.h
> ===================================================================
> --- linux-trace.git.orig/include/trace/events/xen.h
> +++ linux-trace.git/include/trace/events/xen.h
> @@ -147,7 +147,6 @@ DECLARE_EVENT_CLASS(xen_mmu__set_pte,
>   		     TP_ARGS(ptep, pteval))
>   
>   DEFINE_XEN_MMU_SET_PTE(xen_mmu_set_pte);
> -DEFINE_XEN_MMU_SET_PTE(xen_mmu_set_pte_atomic);
>   
>   TRACE_EVENT(xen_mmu_set_pte_at,
>   	    TP_PROTO(struct mm_struct *mm, unsigned long addr,
> @@ -169,21 +168,6 @@ TRACE_EVENT(xen_mmu_set_pte_at,
>   		      (int)sizeof(pteval_t) * 2, (unsigned long long)__entry->pteval)
>   	);
>   
> -TRACE_EVENT(xen_mmu_pte_clear,
> -	    TP_PROTO(struct mm_struct *mm, unsigned long addr, pte_t *ptep),
> -	    TP_ARGS(mm, addr, ptep),
> -	    TP_STRUCT__entry(
> -		    __field(struct mm_struct *, mm)
> -		    __field(unsigned long, addr)
> -		    __field(pte_t *, ptep)
> -		    ),
> -	    TP_fast_assign(__entry->mm = mm;
> -			   __entry->addr = addr;
> -			   __entry->ptep = ptep),
> -	    TP_printk("mm %p addr %lx ptep %p",
> -		      __entry->mm, __entry->addr, __entry->ptep)
> -	);
> -
>   TRACE_DEFINE_SIZEOF(pmdval_t);
>   
>   TRACE_EVENT(xen_mmu_set_pmd,
> @@ -201,6 +185,24 @@ TRACE_EVENT(xen_mmu_set_pmd,
>   		      (int)sizeof(pmdval_t) * 2, (unsigned long long)__entry->pmdval)
>   	);
>   
> +#ifdef CONFIG_X86_PAE
> +DEFINE_XEN_MMU_SET_PTE(xen_mmu_set_pte_atomic);
> +
> +TRACE_EVENT(xen_mmu_pte_clear,
> +	    TP_PROTO(struct mm_struct *mm, unsigned long addr, pte_t *ptep),
> +	    TP_ARGS(mm, addr, ptep),
> +	    TP_STRUCT__entry(
> +		    __field(struct mm_struct *, mm)
> +		    __field(unsigned long, addr)
> +		    __field(pte_t *, ptep)
> +		    ),
> +	    TP_fast_assign(__entry->mm = mm;
> +			   __entry->addr = addr;
> +			   __entry->ptep = ptep),
> +	    TP_printk("mm %p addr %lx ptep %p",
> +		      __entry->mm, __entry->addr, __entry->ptep)
> +	);
> +
>   TRACE_EVENT(xen_mmu_pmd_clear,
>   	    TP_PROTO(pmd_t *pmdp),
>   	    TP_ARGS(pmdp),
> @@ -210,6 +212,7 @@ TRACE_EVENT(xen_mmu_pmd_clear,
>   	    TP_fast_assign(__entry->pmdp = pmdp),
>   	    TP_printk("pmdp %p", __entry->pmdp)
>   	);
> +#endif
>   
>   #if CONFIG_PGTABLE_LEVELS >= 4
>   
>