linux-kernel - Re: [PATCH v7 1/5] drivers/base/node: Optimize memory block registration to reduce boot time

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Message-ID: <b355e72d-0284-4a31-84e3-ae4a79ad922f@redhat.com>
Date: Wed, 4 Jun 2025 11:45:02 +0200
From: David Hildenbrand <david@...hat.com>
To: Andrew Morton <akpm@...ux-foundation.org>,
 Donet Tom <donettom@...ux.ibm.com>
Cc: Mike Rapoport <rppt@...nel.org>, Oscar Salvador <osalvador@...e.de>,
 Zi Yan <ziy@...dia.com>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
 Ritesh Harjani <ritesh.list@...il.com>, linux-mm@...ck.org,
 linux-kernel@...r.kernel.org, "Rafael J . Wysocki" <rafael@...nel.org>,
 Danilo Krummrich <dakr@...nel.org>,
 Jonathan Cameron <Jonathan.Cameron@...wei.com>,
 Alison Schofield <alison.schofield@...el.com>,
 Yury Norov <yury.norov@...il.com>, Dave Jiang <dave.jiang@...el.com>,
 Madhavan Srinivasan <maddy@...ux.ibm.com>, Nilay Shroff
 <nilay@...ux.ibm.com>, linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH v7 1/5] drivers/base/node: Optimize memory block
 registration to reduce boot time

On 04.06.25 05:07, Andrew Morton wrote:
> On Wed, 28 May 2025 12:18:00 -0500 Donet Tom <donettom@...ux.ibm.com> wrote:
> 
>> During node device initialization, `memory blocks` are registered under
>> each NUMA node. The `memory blocks` to be registered are identified using
>> the node’s start and end PFNs, which are obtained from the node's pg_data
> 
> It's quite unconventional to omit the [0/N] changelog.  This omission
> somewhat messed up my processes so I added a one-liner to this.
> 

Yeah, I was assuming that I simply did not get cc'ed on the cover 
letter, but there is actually none.

Donet please add that in the future. git can do this using --cover-letter.

>>
>> ...
>>
>> Test Results on My system with 32TB RAM
>> =======================================
>> 1. Boot time with CONFIG_DEFERRED_STRUCT_PAGE_INIT enabled.
>>
>> Without this patch
>> ------------------
>> Startup finished in 1min 16.528s (kernel)
>>
>> With this patch
>> ---------------
>> Startup finished in 17.236s (kernel) - 78% Improvement
> 
> Well someone is in for a nice surprise.
> 
>> 2. Boot time with CONFIG_DEFERRED_STRUCT_PAGE_INIT disabled.
>>
>> Without this patch
>> ------------------
>> Startup finished in 28.320s (kernel)
> 
> what.  CONFIG_DEFERRED_STRUCT_PAGE_INIT is supposed to make bootup
> faster.

Right, that's weird. Especially that it is still slower after these changes.

CONFIG_DEFERRED_STRUCT_PAGE_INIT should be initializing in parallel 
which ... should be faster.

@Donet, how many CPUs and nodes does your system have? Can you identify 
what is taking longer than without CONFIG_DEFERRED_STRUCT_PAGE_INIT?

-- 
Cheers,

David / dhildenb