percpu: make embedding first chunk allocator check vmalloc space size (6ea529a2) · Commits · 戴 / test

Embedding first chunk allocator maintains the distances between units in the vmalloc area and thus needs vmalloc space to be larger than the maximum distances between units; otherwise, it wouldn't be able to create any dynamic chunks. This patch makes the embedding first chunk allocator check vmalloc space size and if the maximum distance between units is larger than 75% of it, print warning and, if page mapping allocator is available, fail initialization so that the system falls back onto it. This should work around percpu allocation failure problems on certain sparc64 configurations where distances between NUMA nodes are larger than the vmalloc area and makes percpu allocator more robust for future configurations. Signed-off-by:

Tejun Heo <tj@kernel.org>

mm/percpu.c

+18 −2

Original line number	Diff line number	Diff line
		@@ -1786,7 +1786,7 @@ int __init pcpu_embed_first_chunk(size_t reserved_size, ssize_t dyn_size,
		void base = (void )ULONG_MAX;
		void **areas = NULL;
		struct pcpu_alloc_info *ai;
		size_t size_sum, areas_size;
		size_t size_sum, areas_size, max_distance;
		int group, i, rc;

		ai = pcpu_build_alloc_info(reserved_size, dyn_size, atom_size,
		@@ -1836,8 +1836,24 @@ int __init pcpu_embed_first_chunk(size_t reserved_size, ssize_t dyn_size,
		}

		/* base address is now known, determine group base offsets */
		for (group = 0; group < ai->nr_groups; group++)
		max_distance = 0;
		for (group = 0; group < ai->nr_groups; group++) {
		ai->groups[group].base_offset = areas[group] - base;
		max_distance = max(max_distance, ai->groups[group].base_offset);
		}
		max_distance += ai->unit_size;

		/* warn if maximum distance is further than 75% of vmalloc space */
		if (max_distance > (VMALLOC_END - VMALLOC_START) * 3 / 4) {
		pr_warning("PERCPU: max_distance=0x%lx too large for vmalloc "
		"space 0x%lx\n",
		max_distance, VMALLOC_END - VMALLOC_START);
		#ifdef CONFIG_NEED_PER_CPU_PAGE_FIRST_CHUNK
		/* and fail if we have fallback */
		rc = -EINVAL;
		goto out_free;
		#endif
		}

		pr_info("PERCPU: Embedded %zu pages/cpu @%p s%zu r%zu d%zu u%zu\n",
		PFN_DOWN(size_sum), base, ai->static_size, ai->reserved_size,

Admin message