From: Muchun Song <songmuchun@bytedance.com>
To: Michal Hocko <mhocko@suse.com>
Cc: Jonathan Corbet <corbet@lwn.net>,
Mike Kravetz <mike.kravetz@oracle.com>,
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 00/19] Free some vmemmap pages of hugetlb page
Date: Fri, 30 Oct 2020 18:24:25 +0800
Message-ID: <CAMZfGtUoEeJTBYwxYjWJEreHefcO81WhhnvRO7vTb_k+zPCHrg@mail.gmail.com> (raw)
In-Reply-To: <20201030091445.GF1478@dhcp22.suse.cz>
On Fri, Oct 30, 2020 at 5:14 PM Michal Hocko <mhocko@suse.com> wrote:
>
> On Mon 26-10-20 22:50:55, Muchun Song wrote:
> > If we uses the 1G hugetlbpage, we can save 4095 pages. This is a very
> > substantial gain. On our server, run some SPDK/QEMU applications which
> > will use 1000GB hugetlbpage. With this feature enabled, we can save
> > ~16GB(1G hugepage)/~11GB(2MB hugepage) memory.
> [...]
> > 15 files changed, 1091 insertions(+), 165 deletions(-)
> > create mode 100644 include/linux/bootmem_info.h
> > create mode 100644 mm/bootmem_info.c
>
> This is a neat idea but the code footprint is really non trivial. To a
> very tricky code which hugetlb is unfortunately.
>
> Saving 1,6% of memory is definitely interesting especially for 1GB pages
> which tend to be more static and where the savings are more visible.
>
> Anyway, I haven't seen any runtime overhead analysis here. What is the
> price to modify the vmemmap page tables and make them pte rather than
> pmd based (especially for 2MB hugetlb). Also, how expensive is the
> vmemmap page tables reconstruction on the freeing path?
Yeah, I haven't tested the remapping overhead of reserving a hugetlb
page. I can do that. But the overhead is not on the allocation/freeing of
each hugetlb page, it is only once when we reserve some hugetlb pages
through /proc/sys/vm/nr_hugepages. Once the reservation is successful,
the subsequent allocation, freeing and using are the same as before
(not patched). So I think that the overhead is acceptable.
Thanks.
>
> Thanks!
> --
> Michal Hocko
> SUSE Labs
--
Yours,
Muchun
next prev parent reply index
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-26 14:50 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
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 ` Muchun Song [this message]
2020-10-30 15:19 ` [External] " Michal Hocko
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