linux-kernel - Re: [PATCH v8] mm: cma: support sysfs

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Date:   Fri, 26 Mar 2021 18:28:19 +0100
From:   Anders Roxell <anders.roxell@...aro.org>
To:     Minchan Kim <minchan@...nel.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        linux-mm <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Suren Baghdasaryan <surenb@...gle.com>,
        John Dias <joaodias@...gle.com>, jhubbard@...dia.com,
        Matthew Wilcox <willy@...radead.org>, digetx@...il.com,
        Colin Ian King <colin.king@...onical.com>
Subject: Re: [PATCH v8] mm: cma: support sysfs

On Thu, 25 Mar 2021 at 00:09, Minchan Kim <minchan@...nel.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@...il.com>
> Reviewed-by: Dmitry Osipenko <digetx@...il.com>
> Reviewed-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> Reviewed-by: John Hubbard <jhubbard@...dia.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@...onical.com>
> Signed-off-by: Minchan Kim <minchan@...nel.org>

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