On Thu 29-12-16 11:28:02, Jaewon Kim wrote:
> There are many reasons of CMA allocation failure such as EBUSY, ENOMEM, EINTR.
> This patch prints the error value and bitmap status to know available pages
> regarding fragmentation.
>
> This is an ENOMEM example with this patch.
> [ 11.616321] [2: Binder:711_1: 740] cma: cma_alloc: alloc failed, req-size: 256 pages, ret: -12
> [ 11.616365] [2: Binder:711_1: 740] number of available pages: 4+7+7+8+38+166+127=>357 pages, total: 2048 pages
Could you be more specific why this part is useful?
> 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..535aa39 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) {
> + unsigned int nr, nr_total = 0;
> + unsigned long next_set_bit;
> +
> + pr_info("%s: alloc failed, req-size: %zu pages, ret: %d\n",
> + __func__, count, ret);
> + mutex_lock(&cma->lock);
> + printk("number of available pages: ");
> + start = 0;
> + for (;;) {
> + bitmap_no = find_next_zero_bit(cma->bitmap, cma->count, start);
> + next_set_bit = find_next_bit(cma->bitmap, cma->count, bitmap_no);
> + nr = next_set_bit - bitmap_no;
> + if (bitmap_no >= cma->count)
> + break;
> + if (nr_total == 0)
> + printk("%u", nr);
> + else
> + printk("+%u", nr);
> + nr_total += nr;
> + start = bitmap_no + nr;
> + }
> + printk("=>%u pages, total: %lu pages\n", nr_total, cma->count);
> + mutex_unlock(&cma->lock);
> + }
> +
> return page;
> }
>
> --
> 1.9.1
>
> --
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--
Michal Hocko
SUSE Labs
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