From: Mike Kravetz <mike.kravetz@oracle.com>
To: Muchun Song <songmuchun@bytedance.com>
Cc: Jonathan Corbet <corbet@lwn.net>,
Thomas Gleixner <tglx@linutronix.de>,
mingo@redhat.com, bp@alien8.de, x86@kernel.org, hpa@zytor.com,
dave.hansen@linux.intel.com, luto@kernel.org,
Peter Zijlstra <peterz@infradead.org>,
viro@zeniv.linux.org.uk,
Andrew Morton <akpm@linux-foundation.org>,
paulmck@kernel.org, mchehab+huawei@kernel.org,
pawan.kumar.gupta@linux.intel.com,
Randy Dunlap <rdunlap@infradead.org>,
oneukum@suse.com, anshuman.khandual@arm.com, jroedel@suse.de,
Mina Almasry <almasrymina@google.com>,
David Rientjes <rientjes@google.com>,
Matthew Wilcox <willy@infradead.org>,
Xiongchun duan <duanxiongchun@bytedance.com>,
linux-doc@vger.kernel.org, LKML <linux-kernel@vger.kernel.org>,
Linux Memory Management List <linux-mm@kvack.org>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>
Subject: Re: [External] Re: [PATCH v2 07/19] mm/hugetlb: Free the vmemmap pages associated with each hugetlb page
Date: Thu, 29 Oct 2020 14:59:47 -0700 [thread overview]
Message-ID: <21ea37f2-38ca-ce5f-6039-0ee388092f1d@oracle.com> (raw)
In-Reply-To: <CAMZfGtUUkkkeENXOOLPacverqyudxntTenMKrtpfHnLOBJaX5Q@mail.gmail.com>
On 10/28/20 11:13 PM, Muchun Song wrote:
> On Thu, Oct 29, 2020 at 7:42 AM Mike Kravetz <mike.kravetz@oracle.com> wrote:
>>
>> On 10/26/20 7:51 AM, Muchun Song wrote:
>>> +
>>> +static inline spinlock_t *vmemmap_pmd_lockptr(pmd_t *pmd)
>>> +{
>>> + static DEFINE_SPINLOCK(pgtable_lock);
>>> +
>>> + return &pgtable_lock;
>>> +}
>>
>> This is just a global lock. Correct? And hugetlb specific?
>
> Yes, it is a global lock. Originally, I wanted to use the pmd lock(e.g.
> pmd_lockptr()). But we need to allocate memory for the spinlock and
> initialize it when ALLOC_SPLIT_PTLOCKS. It may increase the
> complexity.
>
> And I think that here alloc/free hugetlb pages is not a frequent operation.
> So I finally use a global lock. Maybe it is enough.
>
>>
>> It should be OK as the page table entries for huegtlb pages will not
>> overlap with other entries.
>
> Does "hugetlb specific" mean the pmd lock? or per hugetlb lock?
> If it is pmd lock, this is fine to me. If not, it may not be enough.
> Because the lock also guards the splitting of pmd pgtable.
By "hugetlb specific", I was trying to say that only hugetlb code would
use this lock. It is not a concern now. However, there has been talk
about other code doing something similar to remove struct pages. If that
ever happens then we will need a different locking scheme.
Disregard my statement about there being no overlap. I was confusing
page tables for huge pages with page tables for mappings mmap entries
of huge pages.
--
Mike Kravetz
next prev parent reply other threads:[~2020-10-29 22:00 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-26 14:50 [PATCH v2 00/19] Free some vmemmap pages of hugetlb page Muchun Song
2020-10-26 14:50 ` [PATCH v2 01/19] mm/memory_hotplug: Move bootmem info registration API to bootmem_info.c Muchun Song
2020-10-26 14:50 ` [PATCH v2 02/19] mm/memory_hotplug: Move {get,put}_page_bootmem() " Muchun Song
2020-10-26 14:50 ` [PATCH v2 03/19] mm/hugetlb: Introduce a new config HUGETLB_PAGE_FREE_VMEMMAP Muchun Song
2020-10-29 10:29 ` Oscar Salvador
2020-10-29 13:34 ` [External] " Muchun Song
2020-10-26 14:50 ` [PATCH v2 04/19] mm/hugetlb: Introduce nr_free_vmemmap_pages in the struct hstate Muchun Song
2020-10-27 22:03 ` Mike Kravetz
2020-10-29 13:26 ` Oscar Salvador
2020-10-29 13:41 ` [External] " Muchun Song
2020-10-26 14:51 ` [PATCH v2 05/19] mm/hugetlb: Introduce pgtable allocation/freeing helpers Muchun Song
2020-10-28 0:32 ` Mike Kravetz
2020-10-28 7:26 ` [External] " Muchun Song
2020-10-28 23:42 ` Mike Kravetz
2020-11-05 13:23 ` Oscar Salvador
2020-11-05 16:08 ` [External] " Muchun Song
2020-11-06 9:46 ` Oscar Salvador
2020-11-06 16:43 ` Muchun Song
2020-10-26 14:51 ` [PATCH v2 06/19] mm/bootmem_info: Introduce {free,prepare}_vmemmap_page() Muchun Song
2020-10-26 14:51 ` [PATCH v2 07/19] mm/hugetlb: Free the vmemmap pages associated with each hugetlb page Muchun Song
2020-10-26 16:01 ` Matthew Wilcox
2020-10-27 2:58 ` [External] " Muchun Song
2020-10-28 23:42 ` Mike Kravetz
2020-10-29 6:13 ` [External] " Muchun Song
2020-10-29 21:59 ` Mike Kravetz [this message]
2020-10-30 2:58 ` Muchun Song
2020-10-26 14:51 ` [PATCH v2 08/19] mm/hugetlb: Defer freeing of hugetlb pages Muchun Song
2020-10-26 14:51 ` [PATCH v2 09/19] mm/hugetlb: Allocate the vmemmap pages associated with each hugetlb page Muchun Song
2020-10-26 14:51 ` [PATCH v2 10/19] mm/hugetlb: Introduce remap_huge_page_pmd_vmemmap helper Muchun Song
2020-10-26 14:51 ` [PATCH v2 11/19] mm/hugetlb: Use PG_slab to indicate split pmd Muchun Song
2020-10-26 14:51 ` [PATCH v2 12/19] mm/hugetlb: Support freeing vmemmap pages of gigantic page Muchun Song
2020-10-26 14:51 ` [PATCH v2 13/19] mm/hugetlb: Add a BUILD_BUG_ON to check if struct page size is a power of two Muchun Song
2020-10-26 14:51 ` [PATCH v2 14/19] mm/hugetlb: Clear PageHWPoison on the non-error memory page Muchun Song
2020-10-26 14:51 ` [PATCH v2 15/19] mm/hugetlb: Flush work when dissolving hugetlb page Muchun Song
2020-10-26 14:51 ` [PATCH v2 16/19] mm/hugetlb: Add a kernel parameter hugetlb_free_vmemmap Muchun Song
2020-10-26 14:51 ` [PATCH v2 17/19] mm/hugetlb: Merge pte to huge pmd only for gigantic page Muchun Song
2020-10-26 14:51 ` [PATCH v2 18/19] mm/hugetlb: Gather discrete indexes of tail page Muchun Song
2020-10-26 14:51 ` [PATCH v2 19/19] mm/hugetlb: Add BUILD_BUG_ON to catch invalid usage of tail struct page Muchun Song
2020-10-26 15:53 ` [PATCH v2 00/19] Free some vmemmap pages of hugetlb page Matthew Wilcox
2020-10-27 2:54 ` [External] " Muchun Song
2020-10-30 9:14 ` Michal Hocko
2020-10-30 10:24 ` [External] " Muchun Song
2020-10-30 15:19 ` Michal Hocko
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