On Thu 29-12-16 18:26:38, Jaewon Kim wrote:
>
>
> On 2016년 12월 29일 18:14, Michal Hocko wrote:
> > 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?
> Hi
> Without this patch we do not know why CMA allocation failed.
Yes, I understand the first part
> Additionally in case of ENOMEM, with bitmap status we can figure out that
The code doesn't seem to check for ENOMEM though
> if it is too small CMA region issue or if it is fragmentation issue.
then please describe that in the changelog. If I got it right the above
would tell us that the fragmentation is the problem, right?
> >
> >> Signed-off-by: Jaewon Kim <jaewon31....@samsung.com>
> >> ---
> >> 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: ");
I guess you want pr_info (or maybe pr_debug) here
> >> + 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);
pr_cont
> >> + nr_total += nr;
> >> + start = bitmap_no + nr;
> >> + }
> >> + printk("=>%u pages, total: %lu pages\n", nr_total, cma->count);
pr_cont
> >> + mutex_unlock(&cma->lock);
> >> + }
> >> +
> >> return page;
> >> }
> >>
> >> --
> >> 1.9.1
> >>
> >> --
> >> To unsubscribe, send a message with 'unsubscribe linux-mm' in
> >> the body to majord...@kvack.org. For more info on Linux MM,
> >> see: http://www.linux-mm.org/ .
> >> Don't email: <a href=mailto:"d...@kvack.org";> em...@kvack.org </a>
>
> --
> To unsubscribe, send a message with 'unsubscribe linux-mm' in
> the body to majord...@kvack.org. For more info on Linux MM,
> see: http://www.linux-mm.org/ .
> Don't email: <a href=mailto:"d...@kvack.org";> em...@kvack.org </a>
--
Michal Hocko
SUSE Labs
