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Date:   Tue, 12 Dec 2023 14:14:49 -0800 (PST)
From:   David Rientjes <rientjes@google.com>
To:     Gang Li <gang.li@linux.dev>
cc:     David Hildenbrand <david@redhat.com>,
        Mike Kravetz <mike.kravetz@oracle.com>,
        Muchun Song <muchun.song@linux.dev>,
        Andrew Morton <akpm@linux-foundation.org>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org, ligang.bdlg@bytedance.com
Subject: Re: [RFC PATCH v2 0/5] hugetlb: parallelize hugetlb page init on
 boot
In-Reply-To: <20231208025240.4744-1-gang.li@linux.dev>
Message-ID: <996ba32c-78f0-1807-5e64-af5841a820e7@google.com>
References: <20231208025240.4744-1-gang.li@linux.dev>
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On Fri, 8 Dec 2023, Gang Li wrote:

> Hi all, hugetlb init parallelization has now been updated to v2.
> 
> To David Hildenbrand: padata multithread utilities has been used to reduce
> code complexity.
> 
> To David Rientjes: The patch for measuring time will be separately included
> in the reply. Please test during your free time, thanks.
> 

I'd love to, but what kernel is this based on?  :)  I can't get this to 
apply to any kernels that I have recently benchmarked with.

> # Introduction
> Hugetlb initialization during boot takes up a considerable amount of time.
> For instance, on a 2TB system, initializing 1,800 1GB huge pages takes 1-2
> seconds out of 10 seconds. Initializing 11,776 1GB pages on a 12TB Intel
> host takes 65.2 seconds [1], which is 17.4% of the total 373.78 seconds boot
> time. This is a noteworthy figure.
> 
> Inspired by [2] and [3], hugetlb initialization can also be accelerated
> through parallelization. Kernel already has infrastructure like
> padata_do_multithreaded, this patch uses it to achieve effective results
> by minimal modifications.
> 
> [1] https://lore.kernel.org/all/783f8bac-55b8-5b95-eb6a-11a583675000@google.com/
> [2] https://lore.kernel.org/all/20200527173608.2885243-1-daniel.m.jordan@oracle.com/
> [3] https://lore.kernel.org/all/20230906112605.2286994-1-usama.arif@bytedance.com/
> 
> # Test result
>         test          no patch(ms)   patched(ms)   saved   
>  ------------------- -------------- ------------- -------- 
>   256c2t(4 node) 2M           2624           956   63.57%  
>   256c2t(4 node) 1G           2679          1582   40.95%  
>   128c1t(2 node) 2M           1788           684   61.74%  
>   128c1t(2 node) 1G           3160          1618   48.80%  
> 
> # Change log
> Changes in v2:
> - Reduce complexity with `padata_do_multithreaded`
> - Support 1G hugetlb
> 
> v1:
> - https://lore.kernel.org/all/20231123133036.68540-1-gang.li@linux.dev/
> - parallelize 2M hugetlb initialization with workqueue
> 
> Gang Li (5):
>   hugetlb: code clean for hugetlb_hstate_alloc_pages
>   hugetlb: split hugetlb_hstate_alloc_pages
>   padata: dispatch works on different nodes
>   hugetlb: parallelize 2M hugetlb allocation and initialization
>   hugetlb: parallelize 1G hugetlb initialization
> 
>  include/linux/hugetlb.h |   2 +-
>  include/linux/padata.h  |   2 +
>  kernel/padata.c         |   8 +-
>  mm/hugetlb.c            | 201 +++++++++++++++++++++++++++-------------
>  mm/mm_init.c            |   1 +
>  5 files changed, 148 insertions(+), 66 deletions(-)
> 
> -- 
> 2.30.2
> 
>