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From: Muchun Song <songmuchun@bytedance.com>
To: Mike Kravetz <mike.kravetz@oracle.com>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org,
	Michal Hocko <mhocko@suse.com>, Peter Xu <peterx@redhat.com>,
	Naoya Horiguchi <naoya.horiguchi@linux.dev>,
	James Houghton <jthoughton@google.com>,
	Mina Almasry <almasrymina@google.com>,
	"Aneesh Kumar K . V" <aneesh.kumar@linux.vnet.ibm.com>,
	Anshuman Khandual <anshuman.khandual@arm.com>,
	Paul Walmsley <paul.walmsley@sifive.com>,
	Christian Borntraeger <borntraeger@linux.ibm.com>,
	Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [RFC PATCH 3/3] hugetlb: Lazy page table copies in fork()
Date: Wed, 1 Jun 2022 13:20:30 +0800	[thread overview]
Message-ID: <Ypb3HhYU/bFL7yx7@FVFYT0MHHV2J.googleapis.com> (raw)
In-Reply-To: <20220527225849.284839-4-mike.kravetz@oracle.com>

On Fri, May 27, 2022 at 03:58:49PM -0700, Mike Kravetz wrote:
> Lazy page table copying at fork time was introduced with commit
> d992895ba2b2 ("Lazy page table copies in fork()").  At the time,
> hugetlb was very new and did not support page faulting.  As a result,
> it was excluded.  When full page fault support was added for hugetlb,
> the exclusion was not removed.
> 
> Simply remove the check that prevents lazy copying of hugetlb page
> tables at fork.  Of course, like other mappings this only applies to
> shared mappings.
> 
> Lazy page table copying at fork will be less advantageous for hugetlb
> mappings because:
> - There are fewer page table entries with hugetlb
> - hugetlb pmds can be shared instead of copied
> 
> In any case, completely eliminating the copy at fork time shold speed
> things up.
> 
> Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>

Acked-by: Muchun Song <songmuchun@bytedance.com>

Thanks.



      parent reply	other threads:[~2022-06-01  5:20 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-05-27 22:58 [RFC PATCH 0/3] hugetlb: speed up linear address scanning Mike Kravetz
2022-05-27 22:58 ` [RFC PATCH 1/3] hugetlb: skip to end of PT page mapping when pte not present Mike Kravetz
2022-05-30 10:10   ` Baolin Wang
2022-05-31 16:56     ` Mike Kravetz
2022-06-15 21:22     ` Mike Kravetz
2022-06-16  3:48       ` Baolin Wang
2022-05-30 19:56   ` Peter Xu
2022-05-31  2:04     ` Muchun Song
2022-05-31 17:05       ` Mike Kravetz
2022-06-01  6:58         ` Anshuman Khandual
2022-05-31 17:00     ` Mike Kravetz
2022-06-15 17:27       ` Mike Kravetz
2022-06-15 17:51         ` Peter Xu
2022-05-27 22:58 ` [RFC PATCH 2/3] hugetlb: do not update address in huge_pmd_unshare Mike Kravetz
2022-05-30 10:14   ` Baolin Wang
2022-05-30 15:36   ` Muchun Song
2022-05-31 17:06     ` Mike Kravetz
2022-05-27 22:58 ` [RFC PATCH 3/3] hugetlb: Lazy page table copies in fork() Mike Kravetz
2022-05-31 17:25   ` David Hildenbrand
2022-06-01  5:20   ` Muchun Song [this message]

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