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References: <20210324230759.2213957-1-minchan@kernel.org>
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From:   Anders Roxell <anders.roxell@linaro.org>
Date:   Fri, 26 Mar 2021 18:28:19 +0100
Message-ID: <CADYN=9LZF4zWuV8VA1y3tcoKWzwK3zCJPFL6yDNuvMzGvEVarQ@mail.gmail.com>
Subject: Re: [PATCH v8] mm: cma: support sysfs
To:     Minchan Kim <minchan@kernel.org>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        linux-mm <linux-mm@kvack.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Suren Baghdasaryan <surenb@google.com>,
        John Dias <joaodias@google.com>, jhubbard@nvidia.com,
        Matthew Wilcox <willy@infradead.org>, digetx@gmail.com,
        Colin Ian King <colin.king@canonical.com>
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On Thu, 25 Mar 2021 at 00:09, Minchan Kim <minchan@kernel.org> wrote:
>
> Since CMA is getting used more widely, it's more important to
> keep monitoring CMA statistics for system health since it's
> directly related to user experience.
>
> This patch introduces sysfs statistics for CMA, in order to provide
> some basic monitoring of the CMA allocator.
>
>  * the number of CMA page successful allocations
>  * the number of CMA page allocation failures
>
> These two values allow the user to calcuate the allocation
> failure rate for each CMA area.
>
> e.g.)
>   /sys/kernel/mm/cma/WIFI/alloc_pages_[success|fail]
>   /sys/kernel/mm/cma/SENSOR/alloc_pages_[success|fail]
>   /sys/kernel/mm/cma/BLUETOOTH/alloc_pages_[success|fail]
>
> The cma_stat was intentionally allocated by dynamic allocation
> to harmonize with kobject lifetime management.
> https://lore.kernel.org/linux-mm/YCOAmXqt6dZkCQYs@kroah.com/
>
> Tested-by: Dmitry Osipenko <digetx@gmail.com>
> Reviewed-by: Dmitry Osipenko <digetx@gmail.com>
> Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Reviewed-by: John Hubbard <jhubbard@nvidia.com>
> Link: https://lore.kernel.org/linux-mm/20210316100433.17665-1-colin.king@canonical.com/
> Addresses-Coverity: ("Dereference after null check")
> Signed-off-by: Colin Ian King <colin.king@canonical.com>
> Signed-off-by: Minchan Kim <minchan@kernel.org>

Tested-by: Anders Roxell <anders.roxell@linaro.org>