linux-kernel - Re: [RFC PATCH v1 03/57] mm/memcontrol: Fix seq_buf size to save memory when PAGE

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Message-ID: <20241014130017.GA1021@cmpxchg.org>
Date: Mon, 14 Oct 2024 09:00:17 -0400
From: Johannes Weiner <hannes@...xchg.org>
To: Ryan Roberts <ryan.roberts@....com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
	Anshuman Khandual <anshuman.khandual@....com>,
	Ard Biesheuvel <ardb@...nel.org>,
	Catalin Marinas <catalin.marinas@....com>,
	David Hildenbrand <david@...hat.com>,
	Greg Marsden <greg.marsden@...cle.com>,
	Ivan Ivanov <ivan.ivanov@...e.com>,
	Kalesh Singh <kaleshsingh@...gle.com>,
	Marc Zyngier <maz@...nel.org>, Mark Rutland <mark.rutland@....com>,
	Matthias Brugger <mbrugger@...e.com>,
	Michal Hocko <mhocko@...nel.org>, Miroslav Benes <mbenes@...e.cz>,
	Roman Gushchin <roman.gushchin@...ux.dev>,
	Shakeel Butt <shakeel.butt@...ux.dev>,
	Will Deacon <will@...nel.org>, cgroups@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org
Subject: Re: [RFC PATCH v1 03/57] mm/memcontrol: Fix seq_buf size to save
 memory when PAGE_SIZE is large

On Mon, Oct 14, 2024 at 11:58:10AM +0100, Ryan Roberts wrote:
> Previously the seq_buf used for accumulating the memory.stat output was
> sized at PAGE_SIZE. But the amount of output is invariant to PAGE_SIZE;
> If 4K is enough on a 4K page system, then it should also be enough on a
> 64K page system, so we can save 60K om the static buffer used in
> mem_cgroup_print_oom_meminfo(). Let's make it so.
> 
> This also has the beneficial side effect of removing a place in the code
> that assumed PAGE_SIZE is a compile-time constant. So this helps our
> quest towards supporting boot-time page size selection.
> 
> Signed-off-by: Ryan Roberts <ryan.roberts@....com>

Acked-by: Johannes Weiner <hannes@...xchg.org>