On Mon, Jul 05, 2021 at 11:04:21AM -0700, Jaegeuk Kim wrote:
> On 07/05, Matthew Wilcox wrote:
> > I think freshly allocated pages have a page->private of 0. ie this
> > code in mm/page_alloc.c:
> >
> > page = rmqueue(ac->preferred_zoneref->zone, zone, order,
> > gfp_mask, alloc_flags, ac->migratetype);
> > if (page) {
> > prep_new_page(page, order, gfp_mask, alloc_flags);
> >
> > where prep_new_page() calls post_alloc_hook() which contains:
> > set_page_private(page, 0);
>
> Hmm, I can see it in 4.14 and 5.10 kernel.
>
> The trace is on:
>
> 30875 [ 1065.118750] c3 87 f2fs_migrate_page+0x354/0x45c
> 30876 [ 1065.123872] c3 87 move_to_new_page+0x70/0x30c
> 30877 [ 1065.128813] c3 87 migrate_pages+0x3a0/0x964
> 30878 [ 1065.133583] c3 87 compact_zone+0x608/0xb04
> 30879 [ 1065.138257] c3 87 kcompactd+0x378/0x4ec
> 30880 [ 1065.142664] c3 87 kthread+0x11c/0x12c
> 30881 [ 1065.146897] c3 87 ret_from_fork+0x10/0x18
>
> It seems compaction_alloc() gets a free page which doesn't reset the fields?
I'm not really familiar with the compaction code. Mel, I see a call
to post_alloc_hook() in split_map_pages(). Are there other ways of
getting the compaction code to allocate a page which don't go through
split_map_pages()?
