linux-kernel - Re: [PATCH] mm, x86/mm: Move creating the tlb

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Message-ID: <20250612104115.039a3817@batman.local.home>
Date: Thu, 12 Jun 2025 10:41:15 -0400
From: Steven Rostedt <rostedt@...dmis.org>
To: Dave Hansen <dave.hansen@...el.com>
Cc: LKML <linux-kernel@...r.kernel.org>, Linux trace kernel
 <linux-trace-kernel@...r.kernel.org>, linux-mm@...ck.org, x86@...nel.org,
 Masami Hiramatsu <mhiramat@...nel.org>, Mathieu Desnoyers
 <mathieu.desnoyers@...icios.com>, Dave Hansen
 <dave.hansen@...ux.intel.com>, Andy Lutomirski <luto@...nel.org>, Thomas
 Gleixner <tglx@...utronix.de>, Peter Zijlstra <peterz@...radead.org>,
 Andrew Morton <akpm@...ux-foundation.org>, Lorenzo Stoakes
 <lorenzo.stoakes@...cle.com>, David Hildenbrand <david@...hat.com>,
 Borislav Petkov <bp@...en8.de>
Subject: Re: [PATCH] mm, x86/mm: Move creating the tlb_flush event back to
 x86 code

On Thu, 12 Jun 2025 07:06:47 -0700
Dave Hansen <dave.hansen@...el.com> wrote:

> On 6/12/25 07:03, Steven Rostedt wrote:
> > Remove the events/tlb.h from mm/rmap.c and add the define
> > CREATE_TRACE_POINTS back in the x86 code.
> > 
> > Fixes: 4cc79b3303f22 ("mm/migration: add trace events for base page and HugeTLB migrations")  
> 
> Is this a big enough problem that it deserves a cc:stable@?

That's questionable. Without this patch, some memory is simply wasted.
So it matters how much you care about wasted memory? On memory tight
systems it may make a difference. But it's just one trace event, which
would free up around 5K of memory.

I put in the fixes tag here because it was an obvious mistake that the
header file wasn't removed from rmap.c when the call to the tracepoint
was. Hmm, I think I put in the wrong fixes tag. I should probably be
the other commit:

Fixes: e73ad5ff2f76 ("mm, x86/mm: Make the batched unmap TLB flush API more generic")

-- Steve