Commit 2a8f3f44 authored by Li RongQing's avatar Li RongQing Committed by Andrew Morton
Browse files

mm/hugetlb: retry to allocate for early boot hugepage allocation 

In cloud environments with massive hugepage reservations (95%+ of system
RAM), single-attempt allocation during early boot often fails due to
memory pressure.

Commit 91f386bf ("hugetlb: batch freeing of vmemmap pages")
intensified this by deferring page frees, increase peak memory usage
during allocation.

Introduce a retry mechanism that leverages vmemmap optimization reclaim
(~1.6% memory) when available.  Upon initial allocation failure, the
system retries until successful or no further progress is made, ensuring
reliable hugepage allocation while preserving batched vmemmap freeing
benefits.

Testing on a 256G machine allocating 252G of hugepages:
Before: 128056/129024 hugepages allocated
After:  Successfully allocated all 129024 hugepages

Link: https://lkml.kernel.org/r/20250901082052.3247-1-lirongqing@baidu.com


Signed-off-by: default avatarLi RongQing <lirongqing@baidu.com>
Suggested-by: default avatarDavid Hildenbrand <david@redhat.com>
Acked-by: default avatarDavid Hildenbrand <david@redhat.com>
Cc: Li RongQing <lirongqing@baidu.com>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Oscar Salvador <osalvador@suse.de>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 2b79cb3e

mm/hugetlb.c

+22 −4
Original line number Diff line number Diff line
@@ -3593,10 +3593,9 @@ static unsigned long __init hugetlb_pages_alloc_boot(struct hstate *h) 


	unsigned long jiffies_start;

	unsigned long jiffies_end;

	unsigned long remaining;



	job.thread_fn	= hugetlb_pages_alloc_boot_node;

	job.start	= 0;

	job.size	= h->max_huge_pages;



	/*

	 * job.max_threads is 25% of the available cpu threads by default.
@@ -3620,10 +3619,29 @@ static unsigned long __init hugetlb_pages_alloc_boot(struct hstate *h) 
	}



	job.max_threads	= hugepage_allocation_threads;

	job.min_chunk	= h->max_huge_pages / hugepage_allocation_threads;



	jiffies_start = jiffies;

	do {

		remaining = h->max_huge_pages - h->nr_huge_pages;



		job.start     = h->nr_huge_pages;

		job.size      = remaining;

		job.min_chunk = remaining / hugepage_allocation_threads;

		padata_do_multithreaded(&job);



		if (h->nr_huge_pages == h->max_huge_pages)

			break;



		/*

		 * Retry only if the vmemmap optimization might have been able to free

		 * some memory back to the system.

		 */

		if (!hugetlb_vmemmap_optimizable(h))

			break;



		/* Continue if progress was made in last iteration */

	} while (remaining != (h->max_huge_pages - h->nr_huge_pages));



	jiffies_end = jiffies;



	pr_info("HugeTLB: allocation took %dms with hugepage_allocation_threads=%ld\n",