On 1 Mar 2021, at 10:09, David Hildenbrand wrote:
> The information that some PFNs are busy is:
> a) not helpful for ordinary users: we don't even know *who* called
> alloc_contig_range(). This is certainly not worth a pr_info.*().
> b) not really helpful for debugging: we don't have any details *why*
> these PFNs are busy, and that is what we usually care about.
> c) not complete: there are other cases where we fail alloc_contig_range()
> using different paths that are not getting recorded.
>
> For example, we reach this path once we succeeded in isolating pageblocks,
> but failed to migrate some pages - which can happen easily on
> ZONE_NORMAL (i.e., has_unmovable_pages() is racy) but also on ZONE_MOVABLE
> i.e., we would have to retry longer to migrate).
>
> For example via virtio-mem when unplugging memory, we can create quite
> some noise (especially with ZONE_NORMAL) that is not of interest to
> users - it's expected that some allocations may fail as memory is busy.
>
> Let's just drop that pr_info_ratelimit() and rather implement a dynamic
> debugging mechanism in the future that can give us a better reason why
> alloc_contig_range() failed on specific pages.
>
> Cc: Andrew Morton <[email protected]>
> Cc: Minchan Kim <[email protected]>
> Cc: Oscar Salvador <[email protected]>
> Cc: Michal Hocko <[email protected]>
> Cc: Vlastimil Babka <[email protected]>
> Signed-off-by: David Hildenbrand <[email protected]>
> ---
LGTM. I agree that the printout is not quite useful.
Reviewed-by: Zi Yan <[email protected]>
—
Best Regards,
Yan Zi