linux-kernel - Re: [PATCH 1/2] mm: hugetlb: add hugetlb_alloc

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Message-ID:
 <cf53e173c1b7e2c5f801e4acaa0447c94f53051d.camel@cyberus-technology.de>
Date: Mon, 24 Feb 2025 10:42:33 +0000
From: Thomas Prescher <thomas.prescher@...erus-technology.de>
To: "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>
CC: "linux-mm@...ck.org" <linux-mm@...ck.org>, "corbet@....net"
	<corbet@....net>, "willy@...radead.org" <willy@...radead.org>,
	"muchun.song@...ux.dev" <muchun.song@...ux.dev>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>
Subject: Re: [PATCH 1/2] mm: hugetlb: add hugetlb_alloc_threads cmdline option

On Sat, 2025-02-22 at 18:46 -0800, Andrew Morton wrote:
> 
> I'm all for auto-tuning but yeah, for a boot-time thing like this we
> require a boot-time knob.
> 
> As is often (always) the case, the sad thing is that about five
> people
> in the world know that this exists.  How can we tell our users that
> this new thing is available and possibly useful to them?  We have no
> channel.
> 
> Perhaps in your [2/2] we could be noisier?  
> 
> 	HugeTLB: allocation took 4242ms with
> hugepage_alloc_threads=42
> 
> and with a facility level higher than KERN_DEBUG (can/should we use
> pr_foo() here, btw?).  That should get people curious and poking
> around
> in the documentation and experimenting.

I completely agree with what you are saying. So for v2, I would:

a) change the default from 2 threads per node to 25% of the total
threads per node to make it faster for everyone

b) make it noisier by using pr_info instead of printk(KERN_DEBUG ...)
and also print the number of threads that are used

Anything that I am missing here?