On Fri 30-12-16 16:24:46, Jaewon Kim wrote:
[...]
> >From 7577cc94da3af27907aa6eec590d2ef51e4b9d80 Mon Sep 17 00:00:00 2001
> From: Jaewon Kim <jaewon31.kim@xxxxxxxxxxx>
> Date: Thu, 29 Dec 2016 11:00:16 +0900
> Subject: [PATCH] mm: cma: print allocation failure reason and bitmap status
>
> There are many reasons of CMA allocation failure such as EBUSY, ENOMEM, EINTR.
> But we did not know error reason so far. This patch prints the error value.
>
> Additionally if CONFIG_CMA_DEBUG is enabled, this patch shows bitmap status to
> know available pages. Actually CMA internally try all available regions because
> some regions can be failed because of EBUSY. Bitmap status is useful to know in
> detail on both ENONEM and EBUSY;
> ENOMEM: not tried at all because of no available region
> it could be too small total region or could be fragmentation issue
> EBUSY: tried some region but all failed
>
> This is an ENOMEM example with this patch.
> [ 13.250961] [1: Binder:715_1: 846] cma: cma_alloc: alloc failed, req-size: 256 pages, ret: -12
> Avabile pages also will be shown if CONFIG_CMA_DEBUG is enabled
> [ 13.251052] [1: Binder:715_1: 846] cma: number of available pages: 4@572+7@585+7@601+8@632+38@730+166@1114+127@1921=>357 pages, total: 2048 pages
please mention how to interpret this information.
some more style suggestions below
>
> Signed-off-by: Jaewon Kim <jaewon31.kim@xxxxxxxxxxx>
> ---
> mm/cma.c | 29 ++++++++++++++++++++++++++++-
> 1 file changed, 28 insertions(+), 1 deletion(-)
>
> diff --git a/mm/cma.c b/mm/cma.c
> index c960459..1bcd9db 100644
> --- a/mm/cma.c
> +++ b/mm/cma.c
> @@ -369,7 +369,7 @@ struct page *cma_alloc(struct cma *cma, size_t count, unsigned int align)
> unsigned long start = 0;
> unsigned long bitmap_maxno, bitmap_no, bitmap_count;
> struct page *page = NULL;
> - int ret;
> + int ret = -ENOMEM;
>
> if (!cma || !cma->count)
> return NULL;
> @@ -427,6 +427,33 @@ struct page *cma_alloc(struct cma *cma, size_t count, unsigned int align)
> trace_cma_alloc(pfn, page, count, align);
>
> pr_debug("%s(): returned %p\n", __func__, page);
> +
> + if (ret != 0)
you can simply do
if (!ret) {
pr_info("%s: alloc failed, req-size: %zu pages, ret: %d\n",
__func__, count, ret);
debug_show_cma_areas();
}
return page;
static void debug_show_cma_areas(void)
{
#ifdef CONFIG_CMA_DEBUG
unsigned int nr, nr_total = 0;
unsigned long next_set_bit;
mutex_lock(&cma->lock);
pr_info("number of available pages: ");
start = 0;
for (;;) {
bitmap_no = find_next_zero_bit(cma->bitmap, cma->count, start);
if (bitmap_no >= cma->count)
break;
next_set_bit = find_next_bit(cma->bitmap, cma->count, bitmap_no);
nr = next_set_bit - bitmap_no;
pr_cont("%s%u@%lu", nr_total ? "+" : "", nr, bitmap_no);
nr_total += nr;
start = bitmap_no + nr;
}
pr_cont("=>%u pages, total: %lu pages\n", nr_total, cma->count);
mutex_unlock(&cma->lock);
#endif
}
--
Michal Hocko
SUSE Labs
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