Re: [PATCH v4 7/7] hugetlb: parallelize 1G hugetlb initialization

[Muchun Song]

On 2024/1/18 20:39, Gang Li wrote:
> Optimizing the initialization speed of 1G huge pages through
> parallelization.
>
> 1G hugetlbs are allocated from bootmem, a process that is already
> very fast and does not currently require optimization. Therefore,
> we focus on parallelizing only the initialization phase in
> `gather_bootmem_prealloc`.
>
> Here are some test results:
>          test          no patch(ms)   patched(ms)   saved
>   ------------------- -------------- ------------- --------
>    256c2t(4 node) 1G           4745          2024   57.34%

What does "256c2t" mean?

>    128c1t(2 node) 1G           3358          1712   49.02%
>        12t        1G          77000         18300   76.23%
>
> Signed-off-by: Gang Li <gang.li@xxxxxxxxx>
> Tested-by: David Rientjes <rientjes@xxxxxxxxxx>
> ---
>   include/linux/hugetlb.h |  2 +-
>   mm/hugetlb.c            | 42 +++++++++++++++++++++++++++++++++--------
>   2 files changed, 35 insertions(+), 9 deletions(-)
>
> diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
> index c1ee640d87b1..77b30a8c6076 100644
> --- a/include/linux/hugetlb.h
> +++ b/include/linux/hugetlb.h
> @@ -178,7 +178,7 @@ pte_t *huge_pmd_share(struct mm_struct *mm, struct vm_area_struct *vma,
>   struct address_space *hugetlb_page_mapping_lock_write(struct page *hpage);
>   
>   extern int sysctl_hugetlb_shm_group;
> -extern struct list_head huge_boot_pages;
> +extern struct list_head huge_boot_pages[MAX_NUMNODES];
>   
>   /* arch callbacks */
>   
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index 9b348ba418f5..2f4b77630ada 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -69,7 +69,7 @@ static bool hugetlb_cma_folio(struct folio *folio, unsigned int order)
>   #endif
>   static unsigned long hugetlb_cma_size __initdata;
>   
> -__initdata LIST_HEAD(huge_boot_pages);
> +__initdata struct list_head huge_boot_pages[MAX_NUMNODES];
>   
>   /* for command line parsing */
>   static struct hstate * __initdata parsed_hstate;
> @@ -3301,7 +3301,7 @@ int alloc_bootmem_huge_page(struct hstate *h, int nid)
>   int __alloc_bootmem_huge_page(struct hstate *h, int nid)
>   {
>   	struct huge_bootmem_page *m = NULL; /* initialize for clang */
> -	int nr_nodes, node;
> +	int nr_nodes, node = nid;

Why not use nid directly in the following list_add()?

>   
>   	/* do node specific alloc */
>   	if (nid != NUMA_NO_NODE) {
> @@ -3339,7 +3339,7 @@ int __alloc_bootmem_huge_page(struct hstate *h, int nid)
>   		huge_page_size(h) - PAGE_SIZE);
>   	/* Put them into a private list first because mem_map is not up yet */
>   	INIT_LIST_HEAD(&m->list);
> -	list_add(&m->list, &huge_boot_pages);
> +	list_add(&m->list, &huge_boot_pages[node]);
>   	m->hstate = h;
>   	return 1;
>   }
> @@ -3390,8 +3390,6 @@ static void __init prep_and_add_bootmem_folios(struct hstate *h,
>   	/* Send list for bulk vmemmap optimization processing */
>   	hugetlb_vmemmap_optimize_folios(h, folio_list);
>   
> -	/* Add all new pool pages to free lists in one lock cycle */
> -	spin_lock_irqsave(&hugetlb_lock, flags);
>   	list_for_each_entry_safe(folio, tmp_f, folio_list, lru) {
>   		if (!folio_test_hugetlb_vmemmap_optimized(folio)) {
>   			/*
> @@ -3404,23 +3402,27 @@ static void __init prep_and_add_bootmem_folios(struct hstate *h,
>   					HUGETLB_VMEMMAP_RESERVE_PAGES,
>   					pages_per_huge_page(h));
>   		}
> +		/* Subdivide locks to achieve better parallel performance *
> +		spin_lock_irqsave(&hugetlb_lock, flags);
>   		__prep_account_new_huge_page(h, folio_nid(folio));
>   		enqueue_hugetlb_folio(h, folio);
> +		spin_unlock_irqrestore(&hugetlb_lock, flags);
>   	}
> -	spin_unlock_irqrestore(&hugetlb_lock, flags);
>   }
>   
>   /*
>    * Put bootmem huge pages into the standard lists after mem_map is up.
>    * Note: This only applies to gigantic (order > MAX_PAGE_ORDER) pages.
>    */
> -static void __init gather_bootmem_prealloc(void)
> +static void __init __gather_bootmem_prealloc(unsigned long start, unsigned long end, void *arg)

This function name could be gather_bootmem_prealloc_node.

> +
>   {
> +	int nid = start;
>   	LIST_HEAD(folio_list);
>   	struct huge_bootmem_page *m;
>   	struct hstate *h = NULL, *prev_h = NULL;
>   
> -	list_for_each_entry(m, &huge_boot_pages, list) {
> +	list_for_each_entry(m, &huge_boot_pages[nid], list) {
>   		struct page *page = virt_to_page(m);
>   		struct folio *folio = (void *)page;
>   
> @@ -3453,6 +3455,22 @@ static void __init gather_bootmem_prealloc(void)
>   	prep_and_add_bootmem_folios(h, &folio_list);
>   }
>   
> +static void __init gather_bootmem_prealloc(void)
> +{
> +	struct padata_mt_job job = {
> +		.thread_fn	= __gather_bootmem_prealloc,
> +		.fn_arg		= NULL,
> +		.start		= 0,
> +		.size		= num_node_state(N_MEMORY),
> +		.align		= 1,
> +		.min_chunk	= 1,
> +		.max_threads	= num_node_state(N_MEMORY),
> +		.numa_aware	= true,
> +	};
> +
> +	padata_do_multithreaded(&job);
> +}
> +
>   static void __init hugetlb_hstate_alloc_pages_onenode(struct hstate *h, int nid)
>   {
>   	unsigned long i;
> @@ -3602,6 +3620,14 @@ static void __init hugetlb_hstate_alloc_pages(struct hstate *h)
>   		return;
>   	}
>   
> +	/* hugetlb_hstate_alloc_pages will be called many times, init huge_boot_pages once*/

s/init/initialize/g

And you miss a black right before "*/".

> +	if (huge_boot_pages[0].next == NULL) {

It it not intuitive. I'd like to use a 'initialied' variable
to indicate whether it has been initialized. BTW, it can be
marked as __initdata.

> +		int i = 0;
> +
> +		for (i = 0; i < MAX_NUMNODES; i++)
> +			INIT_LIST_HEAD(&huge_boot_pages[i]);
> +	}
> +
>   	/* do node specific alloc */
>   	if (hugetlb_hstate_alloc_pages_specific_nodes(h))
>   		return;