Re: [PATCH] mm: hugetlb_vmemmap: use bulk allocator in alloc_vmemmap_page_list()

[Muchun Song <muchun.song@linux.dev>]

> On Sep 5, 2023, at 15:32, Kefeng Wang <wangkefeng.wang@huawei.com> wrote:
> On 2023/9/5 15:10, Kefeng Wang wrote:
>> It is needed 4095 pages(1G) or 7 pages(2M) to be allocated once in
>> alloc_vmemmap_page_list(), so let's add a bulk allocator varietas
>> alloc_pages_bulk_list_node() and switch alloc_vmemmap_page_list()
>> to use it to accelerate page allocation.
>> Simple test on arm64's qemu with 1G Hugetlb, 870,842ns vs 3,845,252ns
>> despite the fluctuations, it is still a nice improvement.
>> Tested-by: Yuan Can <yuancan@huawei.com>
>> Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
>> ---
>>  include/linux/gfp.h  | 9 +++++++++
>>  mm/hugetlb_vmemmap.c | 7 ++++++-
>>  2 files changed, 15 insertions(+), 1 deletion(-)
>> diff --git a/include/linux/gfp.h b/include/linux/gfp.h
>> index 665f06675c83..d6e82f15b61f 100644
>> --- a/include/linux/gfp.h
>> +++ b/include/linux/gfp.h
>> @@ -195,6 +195,15 @@ alloc_pages_bulk_list(gfp_t gfp, unsigned long nr_pages, struct list_head *list)
>>   return __alloc_pages_bulk(gfp, numa_mem_id(), NULL, nr_pages, list, NULL);
>>  }
>>  +static inline unsigned long
>> +alloc_pages_bulk_list_node(gfp_t gfp, int nid, unsigned long nr_pages, struct list_head *list)
>> +{
>> + if (nid == NUMA_NO_NODE)
>> + nid = numa_mem_id();
>> +
>> + return __alloc_pages_bulk(gfp, nid, NULL, nr_pages, list, NULL);
>> +}
>> +
>>  static inline unsigned long
>>  alloc_pages_bulk_array(gfp_t gfp, unsigned long nr_pages, struct page **page_array)
>>  {
>> diff --git a/mm/hugetlb_vmemmap.c b/mm/hugetlb_vmemmap.c
>> index 4b9734777f69..699c4fea6b9f 100644
>> --- a/mm/hugetlb_vmemmap.c
>> +++ b/mm/hugetlb_vmemmap.c
>> @@ -384,8 +384,13 @@ static int alloc_vmemmap_page_list(unsigned long start, unsigned long end,
>>   unsigned long nr_pages = (end - start) >> PAGE_SHIFT;
>>   int nid = page_to_nid((struct page *)start);
>>   struct page *page, *next;
>> + unsigned long nr_alloced;
>>  - while (nr_pages--) {
>> + nr_alloced = alloc_pages_bulk_list_node(gfp_mask, nid, nr_pages, list);
>> + if (!nr_alloced)
>> + return -ENOMEM;
>> +
> 
> eh， forget to inc nr_allocated in the fallback patch， will resend

Do not change the judgement, "nr_pages -= nr_alloced;" is enough
and simple.

>> + while (nr_alloced < nr_pages) {
>>   page = alloc_pages_node(nid, gfp_mask, 0);
>>   if (!page)
>>   goto out;