On Mon, Jan 02 2017, Jaewon Kim wrote:
> 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 tries on 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.
> [ 12.415458] [2: Binder:714_1: 744] cma: cma_alloc: alloc failed, req-size: 256 pages, ret: -12
> If CONFIG_CMA_DEBUG is enabled, avabile pages also will be shown as concatenated
> size@position format. So 4@572 means that there are 4 available pages at 572
> position starting from 0 position.
> [ 12.415503] [2: Binder:714_1: 744] cma: number of available pages: 4@572+7@585+7@601+8@632+38@730+166@1114+127@1921=> 357 free of 2048 total pages
>
> Signed-off-by: Jaewon Kim <jaewon31.kim@xxxxxxxxxxx>
> Acked-by: Michal Nazarewicz <mina86@xxxxxxxxxx>
> ---
> mm/cma.c | 34 +++++++++++++++++++++++++++++++++-
> 1 file changed, 33 insertions(+), 1 deletion(-)
>
> diff --git a/mm/cma.c b/mm/cma.c
> index c960459..9e037541 100644
> --- a/mm/cma.c
> +++ b/mm/cma.c
> @@ -353,6 +353,32 @@ int __init cma_declare_contiguous(phys_addr_t base,
> return ret;
> }
>
> +#ifdef CONFIG_CMA_DEBUG
> +static void debug_show_cma_areas(struct cma *cma)
Make it ‘cma_debug_show_areas’. All other functions have ‘cma’ as
prefix so that’s more consistent.
> +{
> + unsigned long next_zero_bit, next_set_bit;
> + unsigned long start = 0;
> + unsigned int nr_zero, nr_total = 0;
> +
> + mutex_lock(&cma->lock);
> + pr_info("number of available pages: ");
> + for (;;) {
> + next_zero_bit = find_next_zero_bit(cma->bitmap, cma->count, start);
> + if (next_zero_bit >= cma->count)
> + break;
> + next_set_bit = find_next_bit(cma->bitmap, cma->count, next_zero_bit);
> + nr_zero = next_set_bit - next_zero_bit;
> + pr_cont("%s%u@%lu", nr_total ? "+" : "", nr_zero, next_zero_bit);
> + nr_total += nr_zero;
> + start = next_zero_bit + nr_zero;
> + }
> + pr_cont("=> %u free of %lu total pages\n", nr_total, cma->count);
> + mutex_unlock(&cma->lock);
> +}
> +#else
> +static inline void debug_show_cma_areas(struct cma *cma) { }
> +#endif
> +
> /**
> * cma_alloc() - allocate pages from contiguous area
> * @cma: Contiguous memory region for which the allocation is performed.
> @@ -369,7 +395,7 @@ 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;
> @@ -426,6 +452,12 @@ struct page *cma_alloc(struct cma *cma, size_t count, unsigned int align)
>
> trace_cma_alloc(pfn, page, count, align);
>
> + if (ret) {
> + pr_info("%s: alloc failed, req-size: %zu pages, ret: %d\n",
> + __func__, count, ret);
> + debug_show_cma_areas(cma);
> + }
> +
> pr_debug("%s(): returned %p\n", __func__, page);
> return page;
> }
> --
>
--
Best regards
ミハウ “𝓶𝓲𝓷𝓪86” ナザレヴイツ
«If at first you don’t succeed, give up skydiving»
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@xxxxxxxxx. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href