linux-kernel - Re: [PATCH v16 08/11] secretmem: add memcg accounting

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Message-ID: <20210126144838.GL308988@casper.infradead.org>
Date:   Tue, 26 Jan 2021 14:48:38 +0000
From:   Matthew Wilcox <willy@...radead.org>
To:     Mike Rapoport <rppt@...nel.org>
Cc:     Michal Hocko <mhocko@...e.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Andy Lutomirski <luto@...nel.org>,
        Arnd Bergmann <arnd@...db.de>, Borislav Petkov <bp@...en8.de>,
        Catalin Marinas <catalin.marinas@....com>,
        Christopher Lameter <cl@...ux.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        David Hildenbrand <david@...hat.com>,
        Elena Reshetova <elena.reshetova@...el.com>,
        "H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
        James Bottomley <jejb@...ux.ibm.com>,
        "Kirill A. Shutemov" <kirill@...temov.name>,
        Mark Rutland <mark.rutland@....com>,
        Mike Rapoport <rppt@...ux.ibm.com>,
        Michael Kerrisk <mtk.manpages@...il.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Rick Edgecombe <rick.p.edgecombe@...el.com>,
        Roman Gushchin <guro@...com>,
        Shakeel Butt <shakeelb@...gle.com>,
        Shuah Khan <shuah@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Tycho Andersen <tycho@...ho.ws>, Will Deacon <will@...nel.org>,
        linux-api@...r.kernel.org, linux-arch@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org,
        linux-nvdimm@...ts.01.org, linux-riscv@...ts.infradead.org,
        x86@...nel.org, Hagen Paul Pfeifer <hagen@...u.net>,
        Palmer Dabbelt <palmerdabbelt@...gle.com>
Subject: Re: [PATCH v16 08/11] secretmem: add memcg accounting

On Mon, Jan 25, 2021 at 11:38:17PM +0200, Mike Rapoport wrote:
> I cannot use __GFP_ACCOUNT because cma_alloc() does not use gfp.
> Besides, kmem accounting with __GFP_ACCOUNT does not seem
> to update stats and there was an explicit request for statistics:
>  
> https://lore.kernel.org/lkml/CALo0P13aq3GsONnZrksZNU9RtfhMsZXGWhK1n=xYJWQizCd4Zw@mail.gmail.com/
> 
> As for (ab)using NR_SLAB_UNRECLAIMABLE_B, as it was already discussed here:
> 
> https://lore.kernel.org/lkml/20201129172625.GD557259@kernel.org/
> 
> I think that a dedicated stats counter would be too much at the moment and
> NR_SLAB_UNRECLAIMABLE_B is the only explicit stat for unreclaimable memory.

That's not true -- Mlocked is also unreclaimable.  And doesn't this
feel more like mlocked memory than unreclaimable slab?  It's also
Unevictable, so could be counted there instead.