On 6/12/19 3:09 AM, Kirill A. Shutemov wrote:
On Tue, Jun 11, 2019 at 10:06:36PM -0700, Yang Shi wrote:
On 6/11/19 7:47 PM, Kirill A. Shutemov wrote:
On Fri, Jun 07, 2019 at 02:07:37PM +0800, Yang Shi wrote:
+ /*
+ * The THP may be not on LRU at this point, e.g. the old page of
+ * NUMA migration. And PageTransHuge is not enough to distinguish
+ * with other compound page, e.g. skb, THP destructor is not used
+ * anymore and will be removed, so the compound order sounds like
+ * the only choice here.
+ */
+ if (PageTransHuge(page) && compound_order(page) == HPAGE_PMD_ORDER) {
What happens if the page is the same order as THP is not THP? Why removing
It may corrupt the deferred split queue since it is never added into the
list, but deleted here.
of destructor is required?
Due to the change to free_transhuge_page() (extracted deferred split queue
manipulation and moved before memcg uncharge since page->mem_cgroup is
needed), it just calls free_compound_page(). So, it sounds pointless to
still keep THP specific destructor.
It looks there is not a good way to tell if the compound page is THP in
free_page path or not, we may keep the destructor just for this?
Other option would be to move mem_cgroup_uncharge(page); from
__page_cache_release() to destructors. Destructors will be able to
call it as it fits.
Yes, it is an option. Since __page_cache_release() is called by
__put_single_page() too, so mem_cgroup_uncharge() has to be called in
both __put_single_page() and the desctructor (free_compound_page() which
is called by both THP and other compound page except HugeTLB). But, it
sounds acceptable IMHO.
