linux-kernel - Re: [PATCH] drivers/base/memory: Avoid overhead from for_each_present_section

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Message-ID: <Z_jS0J4HmEreh-7J@localhost.localdomain>
Date: Fri, 11 Apr 2025 10:29:04 +0200
From: Oscar Salvador <osalvador@...e.de>
To: Gavin Shan <gshan@...hat.com>
Cc: David Hildenbrand <david@...hat.com>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, adityag@...ux.ibm.com,
	donettom@...ux.ibm.com, gregkh@...uxfoundation.org,
	rafael@...nel.org, dakr@...nel.org, akpm@...ux-foundation.org,
	shan.gavin@...il.com
Subject: Re: [PATCH] drivers/base/memory: Avoid overhead from
 for_each_present_section_nr()

On Fri, Apr 11, 2025 at 03:04:16PM +1000, Gavin Shan wrote:
> I think it's a good point. Tried a quick test on a ARM64 machine whose memory
> capacity is 1TB. Leaping 'nr' by 'sections_per_block' improves the performance a bit,
> even it's not too much. The time taken by memory_dev_init() drops from 110ms to 100ms.
> For the IBM Power9 machine (64GB memory) I have, there are not too much space to be
> improved because the time taken by memory_dev_init() is only 10ms. I will post a patch
> for review after this patch gets merged, if you agree.

I have a patch that looked pretty much the same because I wanted to try
it out after commenting it to David, to see the "gains".
On a x86 system with 100GB and memory-blocks spanning 8 sections, I saw
a gain of 12us.
Of course, that kinda of accumulates wrt. memory capacity.

 

-- 
Oscar Salvador
SUSE Labs