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From: Muchun Song In-Reply-To: <20230906211234.GC3612@monkey> Date: Thu, 7 Sep 2023 11:33:18 +0800 Cc: Linux-MM , LKML , Muchun Song , Joao Martins , Oscar Salvador , David Hildenbrand , Miaohe Lin , David Rientjes , Anshuman Khandual , Naoya Horiguchi , Barry Song , Michal Hocko , Matthew Wilcox , Xiongchun Duan , Andrew Morton Content-Transfer-Encoding: quoted-printable Message-Id: References: <20230905214412.89152-1-mike.kravetz@oracle.com> <20230905214412.89152-8-mike.kravetz@oracle.com> <5e091211-9a32-8480-55fb-faff6a0fadef@linux.dev> <38E2F051-E00B-4104-A616-0EEB2729386F@linux.dev> <20230906211234.GC3612@monkey> To: Mike Kravetz X-Migadu-Flow: FLOW_OUT X-Rspam-User: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: F299F1C000E X-Stat-Signature: rnsocjg8drk6wsx44ye4uc1kz9robuuu X-HE-Tag: 1694057641-307459 X-HE-Meta: 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 7RKmsUpK +Mop4TheLq4sWwNtB9Gsr8Wi+fl0VZxFWyMwveQyml+JyuC8QZSNBJ8/VMMSE2QNKyc+6+yIEmx1A3Hn1JuPz4Cl5NsvoKcOPRqXBiNcSlBzehEsnJm4xgEIYm9iUaU/Vkm3aOgzRrehPp98/tPr1nlkuo5u5sWC6vGkD7ViWyVw7oQfIl1fr5LJUw9NLUzlS4kLbynl/BSC+EEPjZOEliw1eq3sAyQQKn7FM X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: > On Sep 7, 2023, at 05:12, Mike Kravetz = wrote: >=20 > On 09/06/23 16:07, Muchun Song wrote: >>> On Sep 6, 2023, at 15:33, Muchun Song wrote: >>> On 2023/9/6 05:44, Mike Kravetz wrote: >>>> When removing hugetlb pages from the pool, we first create a list >>>> of removed pages and then free those pages back to low level = allocators. >>>> Part of the 'freeing process' is to restore vmemmap for all base = pages >>>> if necessary. Pass this list of pages to a new routine >>>> hugetlb_vmemmap_restore_folios() so that vmemmap restoration can be >>>> performed in bulk. >>>>=20 >>>> Signed-off-by: Mike Kravetz >>>> --- >>>> mm/hugetlb.c | 3 +++ >>>> mm/hugetlb_vmemmap.c | 13 +++++++++++++ >>>> mm/hugetlb_vmemmap.h | 5 +++++ >>>> 3 files changed, 21 insertions(+) >>>>=20 >>>> diff --git a/mm/hugetlb.c b/mm/hugetlb.c >>>> index 554be94b07bd..dd2dbc256172 100644 >>>> --- a/mm/hugetlb.c >>>> +++ b/mm/hugetlb.c >>>> @@ -1838,6 +1838,9 @@ static void update_and_free_pages_bulk(struct = hstate *h, struct list_head *list) >>>> { >>>> struct folio *folio, *t_folio; >>>> + /* First restore vmemmap for all pages on list. */ >>>> + hugetlb_vmemmap_restore_folios(h, list); >>>> + >>>> list_for_each_entry_safe(folio, t_folio, list, lru) { >>>> update_and_free_hugetlb_folio(h, folio, false); >>>> cond_resched(); >>>> diff --git a/mm/hugetlb_vmemmap.c b/mm/hugetlb_vmemmap.c >>>> index ac5577d372fe..79de984919ef 100644 >>>> --- a/mm/hugetlb_vmemmap.c >>>> +++ b/mm/hugetlb_vmemmap.c >>>> @@ -481,6 +481,19 @@ int hugetlb_vmemmap_restore(const struct = hstate *h, struct page *head) >>>> return ret; >>>> } >>>> +/* >>>> + * This function will attempt to resore vmemmap for a list of = folios. There >>>> + * is no guarantee that restoration will be successful for all or = any folios. >>>> + * This is used in bulk operations, and no feedback is given to = the caller. >>>> + */ >>>> +void hugetlb_vmemmap_restore_folios(const struct hstate *h, struct = list_head *folio_list) >>>> +{ >>>> + struct folio *folio; >>>> + >>>> + list_for_each_entry(folio, folio_list, lru) >>>> + (void)hugetlb_vmemmap_restore(h, &folio->page); >>>=20 >>> I am curious about the purpose of "void" here, seems it it not = necessnary, >>> ritgh? We cound see so many palces where we do not add the void if = the caller >>> does not care about the return value of the callee. >>=20 >> Another question: should we stop restoring vmemmap pages when >> hugetlb_vmemmap_restore() fails? In which case, I suspect there >> is no memory probably, there is no need to continue, right? >=20 > Recall that the list of hugetlb pages may be from multiple nodes. My = first > thought was that we should continue because memory allocation may fail = on one > node but succeed on another. However, with > = https://lore.kernel.org/linux-mm/20230905031312.91929-1-yuancan@huawei.com= / > memory allocation should fall back to other nodes. So, yes I do = believe it > would make sense to stop when hugetlb_vmemmap_restore returns ENOMEM = as > we are unlikely to make forward progress. Agree. >=20 > Today's behavior will try to restore vmemmap for all pages. No = stopping > on error. >=20 > I have mixed thoughts on this. Quitting on error 'seems reasonable'. > However, if we continue we 'might' be able to allocate vmemmap for one > hugetlb page. And, if we free one hugetlb page that should provide > vmemmap for several more and we may be able to free most pages on the > list. Yes. A good point. But there should be a non-optimized huge page been freed somewhere in parallel, otherwise we still cannot allocate memory. However, the freeing operation happens after = hugetlb_vmemmap_restore_folios. If we want to handle this, we should rework update_and_free_pages_bulk() to do a try when at least a huge pages is freed. Thanks. > --=20 > Mike Kravetz