From: Mike Kravetz <mike.kravetz@oracle.com>
To: Matthew Wilcox <willy@infradead.org>
Cc: Oscar Salvador <osalvador@suse.de>,
Muchun Song <songmuchun@bytedance.com>,
corbet@lwn.net, tglx@linutronix.de, mingo@redhat.com,
bp@alien8.de, x86@kernel.org, hpa@zytor.com,
dave.hansen@linux.intel.com, luto@kernel.org,
peterz@infradead.org, viro@zeniv.linux.org.uk,
akpm@linux-foundation.org, paulmck@kernel.org,
mchehab+huawei@kernel.org, pawan.kumar.gupta@linux.intel.com,
rdunlap@infradead.org, oneukum@suse.com,
anshuman.khandual@arm.com, jroedel@suse.de,
almasrymina@google.com, rientjes@google.com, mhocko@suse.com,
duanxiongchun@bytedance.com, linux-doc@vger.kernel.org,
linux-kernel@vger.kernel.org, linux-mm@kvack.org,
linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH v3 03/21] mm/hugetlb: Introduce a new config HUGETLB_PAGE_FREE_VMEMMAP
Date: Tue, 10 Nov 2020 12:30:48 -0800 [thread overview]
Message-ID: <2aec4539-a55d-4df3-7753-75a33250b6b8@oracle.com> (raw)
In-Reply-To: <20201110195025.GN17076@casper.infradead.org>
On 11/10/20 11:50 AM, Matthew Wilcox wrote:
> On Tue, Nov 10, 2020 at 11:31:31AM -0800, Mike Kravetz wrote:
>> On 11/9/20 5:52 AM, Oscar Salvador wrote:
>>> On Sun, Nov 08, 2020 at 10:10:55PM +0800, Muchun Song wrote:
>
> I don't like config options. I like boot options even less. I don't
> know how to describe to an end-user whether they should select this
> or not. Is there a way to make this not a tradeoff? Or make the
> tradeoff so minimal as to be not worth describing? (do we have numbers
> for the worst possible situation when enabling this option?)
It is not exactly worst case, but Muchun provided some simple benchmarking
results in the cover letter. Quick summary is that hugetlb page creation
and free time is "~2x slower". At first glance, one would say that is
terrible. However, remember that the majority of use cases create hugetlb
pages at or shortly after boot time and add them to the pool. So, additional
overhead is at pool creation time. There is no change to 'normal run time'
operations of getting a page from or returning a page to the pool (think
page fault/unmap).
> I haven't read through these patches in detail, so maybe we do this
> already, but when we free the pages to the buddy allocator, do we retain
> the third page to use for the PTEs (and free pages 3-7), or do we allocate
> a separate page for the PTES and free pages 2-7?
I haven't got there in this latest series. But, in previous revisions the
code did allocate a separate page.
--
Mike Kravetz
next prev parent reply other threads:[~2020-11-10 20:33 UTC|newest]
Thread overview: 54+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-08 14:10 [PATCH v3 00/21] Free some vmemmap pages of hugetlb page Muchun Song
2020-11-08 14:10 ` [PATCH v3 01/21] mm/memory_hotplug: Move bootmem info registration API to bootmem_info.c Muchun Song
2020-11-08 14:10 ` [PATCH v3 02/21] mm/memory_hotplug: Move {get,put}_page_bootmem() " Muchun Song
2020-11-08 14:10 ` [PATCH v3 03/21] mm/hugetlb: Introduce a new config HUGETLB_PAGE_FREE_VMEMMAP Muchun Song
2020-11-09 13:52 ` Oscar Salvador
2020-11-09 14:20 ` [External] " Muchun Song
2020-11-10 19:31 ` Mike Kravetz
2020-11-10 19:50 ` Matthew Wilcox
2020-11-10 20:30 ` Mike Kravetz [this message]
2020-11-17 15:35 ` [External] " Muchun Song
2020-11-11 3:28 ` Muchun Song
2020-11-08 14:10 ` [PATCH v3 04/21] mm/hugetlb: Introduce nr_free_vmemmap_pages in the struct hstate Muchun Song
2020-11-09 16:48 ` Oscar Salvador
2020-11-10 2:42 ` [External] " Muchun Song
2020-11-10 19:38 ` Mike Kravetz
2020-11-11 3:22 ` Muchun Song
2020-11-08 14:10 ` [PATCH v3 05/21] mm/hugetlb: Introduce pgtable allocation/freeing helpers Muchun Song
2020-11-09 17:21 ` Oscar Salvador
2020-11-10 3:49 ` [External] " Muchun Song
2020-11-10 5:42 ` Oscar Salvador
2020-11-10 6:08 ` Muchun Song
2020-11-10 6:33 ` Oscar Salvador
2020-11-10 7:10 ` Muchun Song
2020-11-11 0:47 ` Mike Kravetz
2020-11-11 3:41 ` [External] " Muchun Song
2020-11-13 0:35 ` Mike Kravetz
2020-11-13 1:02 ` Mike Kravetz
2020-11-13 4:18 ` Muchun Song
2020-11-08 14:10 ` [PATCH v3 06/21] mm/bootmem_info: Introduce {free,prepare}_vmemmap_page() Muchun Song
2020-11-08 14:10 ` [PATCH v3 07/21] mm/bootmem_info: Combine bootmem info and type into page->freelist Muchun Song
2020-11-08 14:11 ` [PATCH v3 08/21] mm/vmemmap: Initialize page table lock for vmemmap Muchun Song
2020-11-09 18:11 ` Oscar Salvador
2020-11-10 5:17 ` [External] " Muchun Song
2020-11-08 14:11 ` [PATCH v3 09/21] mm/hugetlb: Free the vmemmap pages associated with each hugetlb page Muchun Song
2020-11-09 18:51 ` Oscar Salvador
2020-11-10 6:40 ` [External] " Muchun Song
2020-11-10 9:48 ` Oscar Salvador
2020-11-10 10:47 ` Muchun Song
2020-11-10 13:52 ` Oscar Salvador
2020-11-10 14:00 ` Muchun Song
2020-11-08 14:11 ` [PATCH v3 10/21] mm/hugetlb: Defer freeing of hugetlb pages Muchun Song
2020-11-08 14:11 ` [PATCH v3 11/21] mm/hugetlb: Allocate the vmemmap pages associated with each hugetlb page Muchun Song
2020-11-08 14:11 ` [PATCH v3 12/21] mm/hugetlb: Introduce remap_huge_page_pmd_vmemmap helper Muchun Song
2020-11-08 14:11 ` [PATCH v3 13/21] mm/hugetlb: Use PG_slab to indicate split pmd Muchun Song
2020-11-08 14:11 ` [PATCH v3 14/21] mm/hugetlb: Support freeing vmemmap pages of gigantic page Muchun Song
2020-11-08 14:11 ` [PATCH v3 15/21] mm/hugetlb: Add a BUILD_BUG_ON to check if struct page size is a power of two Muchun Song
2020-11-08 14:11 ` [PATCH v3 16/21] mm/hugetlb: Set the PageHWPoison to the raw error page Muchun Song
2020-11-08 14:11 ` [PATCH v3 17/21] mm/hugetlb: Flush work when dissolving hugetlb page Muchun Song
2020-11-08 14:11 ` [PATCH v3 18/21] mm/hugetlb: Add a kernel parameter hugetlb_free_vmemmap Muchun Song
2020-11-08 14:11 ` [PATCH v3 19/21] mm/hugetlb: Merge pte to huge pmd only for gigantic page Muchun Song
2020-11-08 14:11 ` [PATCH v3 20/21] mm/hugetlb: Gather discrete indexes of tail page Muchun Song
2020-11-08 14:11 ` [PATCH v3 21/21] mm/hugetlb: Add BUILD_BUG_ON to catch invalid usage of tail struct page Muchun Song
2020-11-10 19:23 ` [PATCH v3 00/21] Free some vmemmap pages of hugetlb page Mike Kravetz
2020-11-11 3:21 ` [External] " Muchun Song
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