linux-kernel - Re: [PATCH v6 09/12] x86/mm: enable broadcast TLB invalidation for multi-threaded processes

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Message-ID: <672ff78c-d93f-48d9-936e-e86b3d9d9dbc@intel.com>
Date: Tue, 21 Jan 2025 10:48:44 -0800
From: Dave Hansen <dave.hansen@...el.com>
To: Peter Zijlstra <peterz@...radead.org>, Rik van Riel <riel@...riel.com>
Cc: x86@...nel.org, linux-kernel@...r.kernel.org, bp@...en8.de,
 dave.hansen@...ux.intel.com, zhengqi.arch@...edance.com,
 nadav.amit@...il.com, thomas.lendacky@....com, kernel-team@...a.com,
 linux-mm@...ck.org, akpm@...ux-foundation.org, jannh@...gle.com,
 mhklinux@...look.com, andrew.cooper3@...rix.com
Subject: Re: [PATCH v6 09/12] x86/mm: enable broadcast TLB invalidation for
 multi-threaded processes

On 1/21/25 01:55, Peter Zijlstra wrote:
> Can't we just start with a very simple constant test and poke at things
> if/when its found to not work?

I'd prefer something simpler for now, too.

Let's just pick a sane number, maybe 16 or 32 for now, make it pokeable
in debugfs and make sure we have a way to tell when the PCID space is
exhausted.

Then we try and design a solution for the _actual_ cases where folks are
exhausting it.