linux-kernel - Re: [PATCH] proc/meminfo: add MemKernel counter

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Message-ID: <20190522155220.GB4374@dhcp22.suse.cz>
Date:   Wed, 22 May 2019 17:52:20 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Konstantin Khlebnikov <khlebnikov@...dex-team.ru>
Cc:     linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
        linux-kernel@...r.kernel.org, Roman Gushchin <guro@...com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Johannes Weiner <hannes@...xchg.org>
Subject: Re: [PATCH] proc/meminfo: add MemKernel counter

On Wed 22-05-19 17:40:09, Konstantin Khlebnikov wrote:
> Some kinds of kernel allocations are not accounted or not show in meminfo.
> For example vmalloc allocations are tracked but overall size is not shown
> for performance reasons. There is no information about network buffers.
> 
> In most cases detailed statistics is not required. At first place we need
> information about overall kernel memory usage regardless of its structure.
> 
> This patch estimates kernel memory usage by subtracting known sizes of
> free, anonymous, hugetlb and caches from total memory size: MemKernel =
> MemTotal - MemFree - Buffers - Cached - SwapCached - AnonPages - Hugetlb.

Why do we need to export something that can be calculated in the
userspace trivially? Also is this really something the number really
meaningful? Say you have a driver that exports memory to the userspace
via mmap but that memory is not accounted. Is this really a kernel
memory?

-- 
Michal Hocko
SUSE Labs