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Date:   Fri, 9 Sep 2022 16:28:59 +0200
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Subject: Re: [RFC PATCH RESEND 20/28] mm: introduce per-VMA lock statistics
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To:     Suren Baghdasaryan <surenb@google.com>, akpm@linux-foundation.org
Cc:     michel@lespinasse.org, jglisse@google.com, mhocko@suse.com,
        vbabka@suse.cz, hannes@cmpxchg.org, mgorman@suse.de,
        dave@stgolabs.net, willy@infradead.org, liam.howlett@oracle.com,
        peterz@infradead.org, laurent.dufour@fr.ibm.com,
        paulmck@kernel.org, luto@kernel.org, songliubraving@fb.com,
        peterx@redhat.com, david@redhat.com, dhowells@redhat.com,
        hughd@google.com, bigeasy@linutronix.de, kent.overstreet@linux.dev,
        rientjes@google.com, axelrasmussen@google.com, joelaf@google.com,
        minchan@google.com, kernel-team@android.com, linux-mm@kvack.org,
        linux-arm-kernel@lists.infradead.org,
        linuxppc-dev@lists.ozlabs.org, x86@kernel.org,
        linux-kernel@vger.kernel.org
References: <20220901173516.702122-1-surenb@google.com>
 <20220901173516.702122-21-surenb@google.com>
From:   Laurent Dufour <ldufour@linux.ibm.com>
In-Reply-To: <20220901173516.702122-21-surenb@google.com>
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Le 01/09/2022 à 19:35, Suren Baghdasaryan a écrit :
> Add a new CONFIG_PER_VMA_LOCK_STATS config option to dump extra
> statistics about handling page fault under VMA lock.
> 

Why not making this a default when per VMA lock are enabled?

> Signed-off-by: Suren Baghdasaryan <surenb@google.com>
> ---
>  include/linux/vm_event_item.h | 6 ++++++
>  include/linux/vmstat.h        | 6 ++++++
>  mm/Kconfig.debug              | 8 ++++++++
>  mm/vmstat.c                   | 6 ++++++
>  4 files changed, 26 insertions(+)
> 
> diff --git a/include/linux/vm_event_item.h b/include/linux/vm_event_item.h
> index f3fc36cd2276..a325783ed05d 100644
> --- a/include/linux/vm_event_item.h
> +++ b/include/linux/vm_event_item.h
> @@ -150,6 +150,12 @@ enum vm_event_item { PGPGIN, PGPGOUT, PSWPIN, PSWPOUT,
>  #ifdef CONFIG_X86
>  		DIRECT_MAP_LEVEL2_SPLIT,
>  		DIRECT_MAP_LEVEL3_SPLIT,
> +#endif
> +#ifdef CONFIG_PER_VMA_LOCK_STATS
> +		VMA_LOCK_SUCCESS,
> +		VMA_LOCK_ABORT,
> +		VMA_LOCK_RETRY,
> +		VMA_LOCK_MISS,
>  #endif
>  		NR_VM_EVENT_ITEMS
>  };
> diff --git a/include/linux/vmstat.h b/include/linux/vmstat.h
> index bfe38869498d..0c2611899cfc 100644
> --- a/include/linux/vmstat.h
> +++ b/include/linux/vmstat.h
> @@ -131,6 +131,12 @@ static inline void vm_events_fold_cpu(int cpu)
>  #define count_vm_vmacache_event(x) do {} while (0)
>  #endif
>  
> +#ifdef CONFIG_PER_VMA_LOCK_STATS
> +#define count_vm_vma_lock_event(x) count_vm_event(x)
> +#else
> +#define count_vm_vma_lock_event(x) do {} while (0)
> +#endif
> +
>  #define __count_zid_vm_events(item, zid, delta) \
>  	__count_vm_events(item##_NORMAL - ZONE_NORMAL + zid, delta)
>  
> diff --git a/mm/Kconfig.debug b/mm/Kconfig.debug
> index ce8dded36de9..075642763a03 100644
> --- a/mm/Kconfig.debug
> +++ b/mm/Kconfig.debug
> @@ -207,3 +207,11 @@ config PTDUMP_DEBUGFS
>  	  kernel.
>  
>  	  If in doubt, say N.
> +
> +
> +config PER_VMA_LOCK_STATS
> +	bool "Statistics for per-vma locks"
> +	depends on PER_VMA_LOCK
> +	help
> +	  Statistics for per-vma locks.
> +	  If in doubt, say N.
> diff --git a/mm/vmstat.c b/mm/vmstat.c
> index 90af9a8572f5..3f3804c846a6 100644
> --- a/mm/vmstat.c
> +++ b/mm/vmstat.c
> @@ -1411,6 +1411,12 @@ const char * const vmstat_text[] = {
>  	"direct_map_level2_splits",
>  	"direct_map_level3_splits",
>  #endif
> +#ifdef CONFIG_PER_VMA_LOCK_STATS
> +	"vma_lock_success",
> +	"vma_lock_abort",
> +	"vma_lock_retry",
> +	"vma_lock_miss",
> +#endif
>  #endif /* CONFIG_VM_EVENT_COUNTERS || CONFIG_MEMCG */
>  };
>  #endif /* CONFIG_PROC_FS || CONFIG_SYSFS || CONFIG_NUMA || CONFIG_MEMCG */