On Mon, 8 Mar 2021 12:20:47 -0800 Minchan Kim <minchan@xxxxxxxxxx> wrote:
> alloc_contig_range is usually used on cma area or movable zone.
> It's critical if the page migration fails on those areas so
> dump more debugging message.
>
> page refcount, mapcount with page flags on dump_page are
> helpful information to deduce the culprit. Furthermore,
> dump_page_owner was super helpful to find long term pinner
> who initiated the page allocation.
>
> Admin could enable the dump like this(by default, disabled)
>
> echo "func dump_migrate_failure_pages +p" > control
>
> Admin could disable it.
>
> echo "func dump_migrate_failure_pages =_" > control
>
> ...
>
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -8453,6 +8453,34 @@ static unsigned long pfn_max_align_up(unsigned long pfn)
> pageblock_nr_pages));
> }
>
> +#if defined(CONFIG_DYNAMIC_DEBUG) || \
> + (defined(CONFIG_DYNAMIC_DEBUG_CORE) && defined(DYNAMIC_DEBUG_MODULE))
> +static DEFINE_RATELIMIT_STATE(alloc_contig_ratelimit_state,
> + DEFAULT_RATELIMIT_INTERVAL, DEFAULT_RATELIMIT_BURST);
> +int alloc_contig_ratelimit(void)
> +{
> + return __ratelimit(&alloc_contig_ratelimit_state);
> +}
Wow, that's an eyesore. We're missing helpers in the ratelimit code.
Can we do something like
/* description goes here */
#define RATELIMIT2(interval, burst)
({
static DEFINE_RATELIMIT_STATE(_rs, interval, burst);
__ratelimit(_rs);
})
#define RATELIMIT()
RATELIMIT2(DEFAULT_RATELIMIT_INTERVAL, DEFAULT_RATELIMIT_BURST)
> +void dump_migrate_failure_pages(struct list_head *page_list)
> +{
> + DEFINE_DYNAMIC_DEBUG_METADATA(descriptor,
> + "migrate failure");
> + if (DYNAMIC_DEBUG_BRANCH(descriptor) &&
> + alloc_contig_ratelimit()) {
> + struct page *page;
> +
> + WARN(1, "failed callstack");
> + list_for_each_entry(page, page_list, lru)
> + dump_page(page, "migration failure");
> + }
> +}
Then we can simply do
if (DYNAMIC_DEBUG_BRANCH(descriptor) && RATELIMIT())
