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

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Message-ID: <9f7ae0e6-4640-418d-a4db-dba594377ac2@linux.ibm.com>
Date: Wed, 4 Jun 2025 18:47:01 +0530
From: Donet Tom <donettom@...ux.ibm.com>
To: David Hildenbrand <david@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>
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 6/4/25 3:15 PM, David Hildenbrand wrote:
> 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.

Sure,

I will add cover letter in next revision.


>
>>>
>>> ...
>>>
>>> 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?



My system has,

CPU      - 1528
Node     - 16
Memory - 31TB

I ran the same test with and without CONFIG_DEFERRED_STRUCT_PAGE_INIT, 
and the boot time was consistently higher with 
CONFIG_DEFERRED_STRUCT_PAGE_INIT enabled.

I'm still investigating this. I'll check further and get back to you.



CONFIG_DEFERRED_STRUCT_PAGE_INIT enabled
----------------------------------------------------------------------
1. Startup finished in 12.959s (kernel)
2. Startup finished in 13.036s (kernel)
3. Startup finished in 12.944s (kernel)


CONFIG_DEFERRED_STRUCT_PAGE_INIT disabled
-----------------------------------------------------------------------
1. Startup finished in 12.234s (kernel)
2. Startup finished in 12.287s (kernel)
3. Startup finished in 12.230s (kernel)

Thanks
Donet