Messages in this thread Patch in this message | | | Date | Tue, 3 Oct 2017 18:29:49 -0400 (EDT) | From | Nicolas Pitre <> | Subject | Re: [PATCH] mm/percpu.c: use smarter memory allocation for struct pcpu_alloc_info |
| |
On Tue, 3 Oct 2017, Tejun Heo wrote:
> On Tue, Oct 03, 2017 at 04:57:44PM -0400, Nicolas Pitre wrote: > > This can be much smaller than a page on very small memory systems. > > Always rounding up the size to a page is wasteful in that case, and > > required alignment is smaller than the memblock default. Let's round > > things up to a page size only when the actual size is >= page size, and > > then it makes sense to page-align for a nicer allocation pattern. > > Isn't that a temporary area which gets freed later during boot?
Hmmm...
It may get freed through 3 different paths where 2 of them are error paths. What looks like a non-error path is in pcpu_embed_first_chunk() called from setup_per_cpu_areas(). But there are two versions of setup_per_cpu_areas(): one for SMP and one for !SMP. And the !SMP case never calls pcpu_free_alloc_info() currently.
I'm not sure i understand that code fully, but maybe the following patch could be a better fit:
----- >8 Subject: [PATCH] percpu: don't forget to free the temporary struct pcpu_alloc_info
Unlike the SMP case, the !SMP case does not free the memory for struct pcpu_alloc_info allocated in setup_per_cpu_areas(). And to give it a chance of being reused by the page allocator later, align it to a page boundary just like its size.
Signed-off-by: Nicolas Pitre <nico@linaro.org>
diff --git a/mm/percpu.c b/mm/percpu.c index 434844415d..caab63375b 100644 --- a/mm/percpu.c +++ b/mm/percpu.c @@ -1416,7 +1416,7 @@ struct pcpu_alloc_info * __init pcpu_alloc_alloc_info(int nr_groups, __alignof__(ai->groups[0].cpu_map[0])); ai_size = base_size + nr_units * sizeof(ai->groups[0].cpu_map[0]); - ptr = memblock_virt_alloc_nopanic(PFN_ALIGN(ai_size), 0); + ptr = memblock_virt_alloc_nopanic(PFN_ALIGN(ai_size), PAGE_SIZE); if (!ptr) return NULL; ai = ptr; @@ -2295,6 +2295,7 @@ void __init setup_per_cpu_areas(void) if (pcpu_setup_first_chunk(ai, fc) < 0) panic("Failed to initialize percpu areas."); + pcpu_free_alloc_info(ai); } #endif /* CONFIG_SMP */
| |