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

[Kefeng Wang <wangkefeng.wang@huawei.com>]

On 2023/9/5 17:23, Muchun Song wrote:
> 
> 
>> 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.

nr_pages = 7,  nr_alloced = 4, new nr_pages = 3, the fallback won't
execute if nr_alloced not cleared, will add nr_allocated only alloc page 
successfully.

         while (nr_allocated < nr_pages) {
                 page = alloc_pages_node(nid, gfp_mask, 0);
                 if (!page)
                         goto out;
                 list_add_tail(&page->lru, list);
+               nr_allocated++;
         }

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