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Message-Id: <20211015141310.f69c5fbf0eb910ad0a43ebd5@linux-foundation.org>
Date: Fri, 15 Oct 2021 14:13:10 -0700
From: Andrew Morton <akpm@...ux-foundation.org>
To: Chen Wandun <chenwandun@...wei.com>
Cc: <shakeelb@...gle.com>, <npiggin@...il.com>, <linux-mm@...ck.org>,
<linux-kernel@...r.kernel.org>, <edumazet@...gle.com>,
<wangkefeng.wang@...wei.com>, <guohanjun@...wei.com>
Subject: Re: [PATCH] mm/vmalloc: introduce alloc_pages_bulk_array_mempolicy
to accelerate memory allocation
On Thu, 14 Oct 2021 17:29:52 +0800 Chen Wandun <chenwandun@...wei.com> wrote:
> It will cause significant performance regressions in some situations
> as Andrew mentioned in [1]. The main situation is vmalloc, vmalloc
> will allocate pages with NUMA_NO_NODE by default, that will result
> in alloc page one by one;
>
> In order to solve this, __alloc_pages_bulk and mempolicy should be
> considered at the same time.
>
> 1) If node is specified in memory allocation request, it will alloc
> all pages by __alloc_pages_bulk.
>
> 2) If interleaving allocate memory, it will cauculate how many pages
> should be allocated in each node, and use __alloc_pages_bulk to alloc
> pages in each node.
>
> [1]: https://lore.kernel.org/lkml/CALvZod4G3SzP3kWxQYn0fj+VgG-G3yWXz=gz17+3N57ru1iajw@mail.gmail.com/t/#m750c8e3231206134293b089feaa090590afa0f60
>
> ...
>
> --- a/include/linux/gfp.h
> +++ b/include/linux/gfp.h
> @@ -531,6 +531,10 @@ unsigned long __alloc_pages_bulk(gfp_t gfp, int preferred_nid,
> struct list_head *page_list,
> struct page **page_array);
>
> +unsigned long alloc_pages_bulk_array_mempolicy(gfp_t gfp,
> + unsigned long nr_pages,
> + struct page **page_array);
> +
> /* Bulk allocate order-0 pages */
> static inline unsigned long
> alloc_pages_bulk_list(gfp_t gfp, unsigned long nr_pages, struct list_head *list)
> diff --git a/mm/mempolicy.c b/mm/mempolicy.c
> index 9f8cd1457829..f456c5eb8d10 100644
> --- a/mm/mempolicy.c
> +++ b/mm/mempolicy.c
> @@ -2196,6 +2196,82 @@ struct page *alloc_pages(gfp_t gfp, unsigned order)
> }
> EXPORT_SYMBOL(alloc_pages);
>
> +unsigned long alloc_pages_bulk_array_interleave(gfp_t gfp,
> + struct mempolicy *pol, unsigned long nr_pages,
> + struct page **page_array)
I'll make this static.
> +{
> + int nodes;
> + unsigned long nr_pages_per_node;
> + int delta;
> + int i;
> + unsigned long nr_allocated;
> + unsigned long total_allocated = 0;
> +
> + nodes = nodes_weight(pol->nodes);
> + nr_pages_per_node = nr_pages / nodes;
> + delta = nr_pages - nodes * nr_pages_per_node;
> +
> + for (i = 0; i < nodes; i++) {
> + if (delta) {
> + nr_allocated = __alloc_pages_bulk(gfp,
> + interleave_nodes(pol), NULL,
> + nr_pages_per_node + 1, NULL,
> + page_array);
> + delta--;
> + } else {
> + nr_allocated = __alloc_pages_bulk(gfp,
> + interleave_nodes(pol), NULL,
> + nr_pages_per_node, NULL, page_array);
> + }
> +
> + page_array += nr_allocated;
> + total_allocated += nr_allocated;
> + }
> +
> + return total_allocated;
> +}
> +
> +unsigned long alloc_pages_bulk_array_preferred_many(gfp_t gfp, int nid,
> + struct mempolicy *pol, unsigned long nr_pages,
> + struct page **page_array)
And this.
> +{
> + gfp_t preferred_gfp;
> + unsigned long nr_allocated = 0;
> +
> + preferred_gfp = gfp | __GFP_NOWARN;
> + preferred_gfp &= ~(__GFP_DIRECT_RECLAIM | __GFP_NOFAIL);
> +
> + nr_allocated = __alloc_pages_bulk(preferred_gfp, nid, &pol->nodes,
> + nr_pages, NULL, page_array);
> +
> + if (nr_allocated < nr_pages)
> + nr_allocated += __alloc_pages_bulk(gfp, numa_node_id(), NULL,
> + nr_pages - nr_allocated, NULL,
> + page_array + nr_allocated);
> + return nr_allocated;
> +}
> +
> +unsigned long alloc_pages_bulk_array_mempolicy(gfp_t gfp,
> + unsigned long nr_pages, struct page **page_array)
> +{
> + struct mempolicy *pol = &default_policy;
> +
> + if (!in_interrupt() && !(gfp & __GFP_THISNODE))
> + pol = get_task_policy(current);
> +
> + if (pol->mode == MPOL_INTERLEAVE)
> + return alloc_pages_bulk_array_interleave(gfp, pol,
> + nr_pages, page_array);
> +
> + if (pol->mode == MPOL_PREFERRED_MANY)
> + return alloc_pages_bulk_array_preferred_many(gfp,
> + numa_node_id(), pol, nr_pages, page_array);
> +
> + return __alloc_pages_bulk(gfp, policy_node(gfp, pol, numa_node_id()),
> + policy_nodemask(gfp, pol), nr_pages, NULL,
> + page_array);
> +}
Some documentation via code comments would be nice. If only for
alloc_pages_bulk_array_mempolicy(). Mainly to explain why it exists.
I suppose the internal functions can be left uncommented if they're
sufficiently obvious?
> struct folio *folio_alloc(gfp_t gfp, unsigned order)
> {
> struct page *page = alloc_pages(gfp | __GFP_COMP, order);
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index b7ac4a8fe2b3..49adba793f3c 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -2856,23 +2856,14 @@ vm_area_alloc_pages(gfp_t gfp, int nid,
> */
> nr_pages_request = min(100U, nr_pages - nr_allocated);
>
> - if (nid == NUMA_NO_NODE) {
> - for (i = 0; i < nr_pages_request; i++) {
> - page = alloc_page(gfp);
> - if (page)
> - pages[nr_allocated + i] = page;
> - else {
> - nr = i;
> - break;
> - }
> - }
> - if (i >= nr_pages_request)
> - nr = nr_pages_request;
> - } else {
> + if (nid == NUMA_NO_NODE)
> + nr = alloc_pages_bulk_array_mempolicy(gfp,
> + nr_pages_request,
> + pages + nr_allocated);
> + else
> nr = alloc_pages_bulk_array_node(gfp, nid,
> nr_pages_request,
> pages + nr_allocated);
> - }
> nr_allocated += nr;
> cond_resched();
>
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