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Message-ID: <9d5de524-28ee-4d71-9493-f77967ea213c@redhat.com>
Date:   Fri, 24 Nov 2023 20:47:43 +0100
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Subject: Re: [RFC PATCH v1 0/4] hugetlb: parallelize hugetlb page allocation
 on boot
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To:     David Rientjes <rientjes@google.com>
Cc:     Gang Li <gang.li@linux.dev>,
        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, Gang Li <ligang.bdlg@bytedance.com>
References: <20231123133036.68540-1-gang.li@linux.dev>
 <5c0e27f2-5826-4537-a1ab-1debfab65b9a@redhat.com>
 <28e28c2a-e72d-a181-e87a-39cecc8c3c76@google.com>
From:   David Hildenbrand <david@redhat.com>
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On 24.11.23 20:44, David Rientjes wrote:
> On Thu, 23 Nov 2023, David Hildenbrand wrote:
> 
>> On 23.11.23 14:30, Gang Li wrote:
>>> From: Gang Li <ligang.bdlg@bytedance.com>
>>>
>>> Inspired by these patches [1][2], this series aims to speed up the
>>> initialization of hugetlb during the boot process through
>>> parallelization.
>>>
>>> It is particularly effective in large systems. On a machine equipped
>>> with 1TB of memory and two NUMA nodes, the time for hugetlb
>>> initialization was reduced from 2 seconds to 1 second.
>>
>> Sorry to say, but why is that a scenario worth adding complexity for /
>> optimizing for? You don't cover that, so there is a clear lack in the
>> motivation.
>>
>> 2 vs. 1 second on a 1 TiB system is usually really just noise.
>>
> 
> The cost will continue to grow over time, so I presume that Gang is trying
> to get out in front of the issue even though it may not be a large savings
> today.
> 
> Running single boot tests, with the latest upstream kernel, allocating
> 1,440 1GB hugetlb pages on a 1.5TB AMD host appears to take 1.47s.
> 
> But allocating 11,776 1GB hugetlb pages on a 12TB Intel host takes 65.2s
> today with the current implementation.

And there, the 65.2s won't be noise because that 12TB system is up by a 
snap of a finger? :)

-- 
Cheers,

David / dhildenb