| Message ID | 20210329183312.178266-6-shy828301@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | mm: thp: use generic THP migration for NUMA hinting fault | expand |
On Mon, 29 Mar 2021 11:33:11 -0700 Yang Shi <shy828301@gmail.com> wrote: > The old behavior didn't split THP if migration is failed due to lack of > memory on the target node. But the THP migration does split THP, so keep > the old behavior for misplaced NUMA page migration. > > Signed-off-by: Yang Shi <shy828301@gmail.com> > --- > mm/migrate.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/mm/migrate.c b/mm/migrate.c > index 86325c750c14..1c0c873375ab 100644 > --- a/mm/migrate.c > +++ b/mm/migrate.c > @@ -1444,6 +1444,7 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page, > int swapwrite = current->flags & PF_SWAPWRITE; > int rc, nr_subpages; > LIST_HEAD(ret_pages); > + bool nosplit = (reason == MR_NUMA_MISPLACED); > > if (!swapwrite) > current->flags |= PF_SWAPWRITE; > @@ -1495,7 +1496,7 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page, > */ > case -ENOSYS: > /* THP migration is unsupported */ > - if (is_thp) { > + if (is_thp && !nosplit) { This is the "THP migration is unsupported" case, but according to your description you rather want to change the -ENOMEM case? Could this be the correct place to trigger THP split for NUMA balancing, for architectures not supporting THP migration, like s390? Do I understand it correctly that this change (for -ENOSYS) would result in always failed THP migrations during NUMA balancing, if THP migration was not supported?
On Tue, Mar 30, 2021 at 7:42 AM Gerald Schaefer <gerald.schaefer@linux.ibm.com> wrote: > > On Mon, 29 Mar 2021 11:33:11 -0700 > Yang Shi <shy828301@gmail.com> wrote: > > > The old behavior didn't split THP if migration is failed due to lack of > > memory on the target node. But the THP migration does split THP, so keep > > the old behavior for misplaced NUMA page migration. > > > > Signed-off-by: Yang Shi <shy828301@gmail.com> > > --- > > mm/migrate.c | 3 ++- > > 1 file changed, 2 insertions(+), 1 deletion(-) > > > > diff --git a/mm/migrate.c b/mm/migrate.c > > index 86325c750c14..1c0c873375ab 100644 > > --- a/mm/migrate.c > > +++ b/mm/migrate.c > > @@ -1444,6 +1444,7 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page, > > int swapwrite = current->flags & PF_SWAPWRITE; > > int rc, nr_subpages; > > LIST_HEAD(ret_pages); > > + bool nosplit = (reason == MR_NUMA_MISPLACED); > > > > if (!swapwrite) > > current->flags |= PF_SWAPWRITE; > > @@ -1495,7 +1496,7 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page, > > */ > > case -ENOSYS: > > /* THP migration is unsupported */ > > - if (is_thp) { > > + if (is_thp && !nosplit) { > > This is the "THP migration is unsupported" case, but according to your > description you rather want to change the -ENOMEM case? > > Could this be the correct place to trigger THP split for NUMA balancing, > for architectures not supporting THP migration, like s390? Yes, I think it could be as I mentioned in the previous email. > > Do I understand it correctly that this change (for -ENOSYS) would > result in always failed THP migrations during NUMA balancing, if THP > migration was not supported? Yes.
diff --git a/mm/migrate.c b/mm/migrate.c index 86325c750c14..1c0c873375ab 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -1444,6 +1444,7 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page, int swapwrite = current->flags & PF_SWAPWRITE; int rc, nr_subpages; LIST_HEAD(ret_pages); + bool nosplit = (reason == MR_NUMA_MISPLACED); if (!swapwrite) current->flags |= PF_SWAPWRITE; @@ -1495,7 +1496,7 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page, */ case -ENOSYS: /* THP migration is unsupported */ - if (is_thp) { + if (is_thp && !nosplit) { if (!try_split_thp(page, &page2, from)) { nr_thp_split++; goto retry;
The old behavior didn't split THP if migration is failed due to lack of memory on the target node. But the THP migration does split THP, so keep the old behavior for misplaced NUMA page migration. Signed-off-by: Yang Shi <shy828301@gmail.com> --- mm/migrate.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)