linux-kernel - Re: [PATCH 16/26] mm: asi: Map non-user buddy allocations as nonsensitive

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Message-ID: <CA+i-1C31FuFUkCMZmZ7O7423f_e-0RAEcBiMMsO4daTACVZjiw@mail.gmail.com>
Date: Wed, 21 Aug 2024 15:59:11 +0200
From: Brendan Jackman <jackmanb@...gle.com>
To: Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, 
	Dave Hansen <dave.hansen@...ux.intel.com>, "H. Peter Anvin" <hpa@...or.com>, 
	Andy Lutomirski <luto@...nel.org>, Peter Zijlstra <peterz@...radead.org>, 
	Sean Christopherson <seanjc@...gle.com>, Paolo Bonzini <pbonzini@...hat.com>, 
	Alexandre Chartre <alexandre.chartre@...cle.com>, 
	Jan Setje-Eilers <jan.setjeeilers@...cle.com>, Catalin Marinas <catalin.marinas@....com>, 
	Will Deacon <will@...nel.org>, Mark Rutland <mark.rutland@....com>, 
	Andrew Morton <akpm@...ux-foundation.org>, Mel Gorman <mgorman@...e.de>, 
	Lorenzo Stoakes <lstoakes@...il.com>, David Hildenbrand <david@...hat.com>, Vlastimil Babka <vbabka@...e.cz>, 
	Michal Hocko <mhocko@...nel.org>, Juri Lelli <juri.lelli@...hat.com>, 
	Vincent Guittot <vincent.guittot@...aro.org>, Dietmar Eggemann <dietmar.eggemann@....com>, 
	Steven Rostedt <rostedt@...dmis.org>, Valentin Schneider <vschneid@...hat.com>, Paul Turner <pjt@...gle.com>, 
	Reiji Watanabe <reijiw@...gle.com>, Junaid Shahid <junaids@...gle.com>, Ofir Weisse <oweisse@...gle.com>, 
	Yosry Ahmed <yosryahmed@...gle.com>, Patrick Bellasi <derkling@...gle.com>, 
	KP Singh <kpsingh@...gle.com>, Alexandra Sandulescu <aesa@...gle.com>, 
	Matteo Rizzo <matteorizzo@...gle.com>, Jann Horn <jannh@...gle.com>
Cc: x86@...nel.org, linux-kernel@...r.kernel.org, linux-mm@...ck.org, 
	kvm@...r.kernel.org
Subject: Re: [PATCH 16/26] mm: asi: Map non-user buddy allocations as nonsensitive

> This solution is silly for at least the following reasons:
>
> - If the async queue gets long, we'll run out of allocatable memory.
> - We don't batch the TLB flushing or worker wakeups at all.
> - We drop FPI flags and skip the pcplists.

While fiddling with this code I just noticed that, in my enthusiasm
for stripping the logic to the bare functional minimum, I went
overboard and totally removed the logic to wake up the kworker.

Anyway, this patch is stupid regardless for the reasons above, but
just noting this down in case anyone does read it and wonder how it
can possibly work. It just leaks memory.

If anyone wants to try out this RFC and needs their system to stay
alive for a while, let me know and I'll prepare a branch with this
issue fixed.