| Message ID | 20211001175210.45968-6-mike.kravetz@oracle.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | hugetlb: add demote/split page functionality | expand |
On Fri, Oct 01, 2021 at 10:52:10AM -0700, Mike Kravetz wrote: > Demote page functionality will split a huge page into a number of huge > pages of a smaller size. For example, on x86 a 1GB huge page can be > demoted into 512 2M huge pages. Demotion is done 'in place' by simply > splitting the huge page. > > Added '*_for_demote' wrappers for remove_hugetlb_page, > destroy_compound_gigantic_page and prep_compound_gigantic_page for use > by demote code. > > Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com> > --- > mm/hugetlb.c | 82 +++++++++++++++++++++++++++++++++++++++++++++++----- > 1 file changed, 74 insertions(+), 8 deletions(-) > ... > +static int demote_free_huge_page(struct hstate *h, struct page *page) > +{ > + int i, nid = page_to_nid(page); > + struct hstate *target_hstate; > + int rc = 0; > + > + target_hstate = size_to_hstate(PAGE_SIZE << h->demote_order); > + > + remove_hugetlb_page_for_demote(h, page, false); > + spin_unlock_irq(&hugetlb_lock); > + > + rc = alloc_huge_page_vmemmap(h, page); > + if (rc) { > + /* Allocation of vmemmmap failed, we can not demote page */ > + spin_lock_irq(&hugetlb_lock); > + set_page_refcounted(page); > + add_hugetlb_page(h, page, false); > + return rc; > + } Question: You keep the original error code returned from alloc_huge_page_vmemmap() here, but then you lose it on demote_pool_huge_page() when doing the !demote_free_huge_page. Would not make more sense to keep it all the way down to demote_store() in case you want to return the actual error code? > + > + /* > + * Use destroy_compound_gigantic_page_for_demote for all huge page > + * sizes as it will not ref count pages. > + */ > + destroy_compound_gigantic_page_for_demote(page, huge_page_order(h)); It seems that for now we only allow gigantic pages to be demoted, but destroy_compound_gigantic_page_for_demote feels kind of wrong, even if it is only a wrapper that ends up calling _*gigantic_ functions. We want a routine that destroy a hugetlb to be demoted into smaller hugetlb pages, so the name gigantic makes little sense to appear in my opinion. > static int demote_pool_huge_page(struct hstate *h, nodemask_t *nodes_allowed) > __must_hold(&hugetlb_lock) > { > + int nr_nodes, node; > + struct page *page; > int rc = 0; > > lockdep_assert_held(&hugetlb_lock); > @@ -3313,9 +3377,15 @@ static int demote_pool_huge_page(struct hstate *h, nodemask_t *nodes_allowed) > if (!h->demote_order) > return rc; > > - /* > - * TODO - demote fucntionality will be added in subsequent patch > - */ > + for_each_node_mask_to_free(h, nr_nodes, node, nodes_allowed) { > + if (!list_empty(&h->hugepage_freelists[node])) { > + page = list_entry(h->hugepage_freelists[node].next, > + struct page, lru); > + rc = !demote_free_huge_page(h, page); I kinda dislike this as I pointed out.
On 10/6/21 1:41 AM, Oscar Salvador wrote: > On Fri, Oct 01, 2021 at 10:52:10AM -0700, Mike Kravetz wrote: >> Demote page functionality will split a huge page into a number of huge >> pages of a smaller size. For example, on x86 a 1GB huge page can be >> demoted into 512 2M huge pages. Demotion is done 'in place' by simply >> splitting the huge page. >> >> Added '*_for_demote' wrappers for remove_hugetlb_page, >> destroy_compound_gigantic_page and prep_compound_gigantic_page for use >> by demote code. >> >> Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com> >> --- >> mm/hugetlb.c | 82 +++++++++++++++++++++++++++++++++++++++++++++++----- >> 1 file changed, 74 insertions(+), 8 deletions(-) >> > ... >> +static int demote_free_huge_page(struct hstate *h, struct page *page) >> +{ >> + int i, nid = page_to_nid(page); >> + struct hstate *target_hstate; >> + int rc = 0; >> + >> + target_hstate = size_to_hstate(PAGE_SIZE << h->demote_order); >> + >> + remove_hugetlb_page_for_demote(h, page, false); >> + spin_unlock_irq(&hugetlb_lock); >> + >> + rc = alloc_huge_page_vmemmap(h, page); >> + if (rc) { >> + /* Allocation of vmemmmap failed, we can not demote page */ >> + spin_lock_irq(&hugetlb_lock); >> + set_page_refcounted(page); >> + add_hugetlb_page(h, page, false); >> + return rc; >> + } > > Question: You keep the original error code returned from alloc_huge_page_vmemmap() > here, but then you lose it on demote_pool_huge_page() when doing the > !demote_free_huge_page. Would not make more sense to keep it all the way down to > demote_store() in case you want to return the actual error code? > Yes, I will return it all the way to demote_store (and the user). >> + >> + /* >> + * Use destroy_compound_gigantic_page_for_demote for all huge page >> + * sizes as it will not ref count pages. >> + */ >> + destroy_compound_gigantic_page_for_demote(page, huge_page_order(h)); > > It seems that for now we only allow gigantic pages to be demoted, but > destroy_compound_gigantic_page_for_demote feels kind of wrong, even > if it is only a wrapper that ends up calling _*gigantic_ functions. > > We want a routine that destroy a hugetlb to be demoted into smaller hugetlb > pages, so the name gigantic makes little sense to appear in my opinion. > Agree, I do not love the name. Since it is only a wrapper, how about destroy_hugetlb_page_for_demote? And, change those other *_for_demote wrappers to similiarly not have gigantic in their names. >> static int demote_pool_huge_page(struct hstate *h, nodemask_t *nodes_allowed) >> __must_hold(&hugetlb_lock) >> { >> + int nr_nodes, node; >> + struct page *page; >> int rc = 0; >> >> lockdep_assert_held(&hugetlb_lock); >> @@ -3313,9 +3377,15 @@ static int demote_pool_huge_page(struct hstate *h, nodemask_t *nodes_allowed) >> if (!h->demote_order) >> return rc; >> >> - /* >> - * TODO - demote fucntionality will be added in subsequent patch >> - */ >> + for_each_node_mask_to_free(h, nr_nodes, node, nodes_allowed) { >> + if (!list_empty(&h->hugepage_freelists[node])) { >> + page = list_entry(h->hugepage_freelists[node].next, >> + struct page, lru); >> + rc = !demote_free_huge_page(h, page); > > I kinda dislike this as I pointed out. > Will change. Thanks for all your comments!
On Wed, Oct 06, 2021 at 11:52:33AM -0700, Mike Kravetz wrote: > Agree, I do not love the name. Since it is only a wrapper, how about > destroy_hugetlb_page_for_demote? And, change those other *_for_demote > wrappers to similiarly not have gigantic in their names. Yes, makes sense to me. We want the names to be generic and not tied to gigantic stuff. Thanks Mike
diff --git a/mm/hugetlb.c b/mm/hugetlb.c index ccbe323c992b..aec2e737d0cd 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -1270,7 +1270,7 @@ static int hstate_next_node_to_free(struct hstate *h, nodemask_t *nodes_allowed) ((node = hstate_next_node_to_free(hs, mask)) || 1); \ nr_nodes--) -#ifdef CONFIG_ARCH_HAS_GIGANTIC_PAGE +/* used to demote non-gigantic_huge pages as well */ static void __destroy_compound_gigantic_page(struct page *page, unsigned int order, bool demote) { @@ -1293,6 +1293,13 @@ static void __destroy_compound_gigantic_page(struct page *page, __ClearPageHead(page); } +static void destroy_compound_gigantic_page_for_demote(struct page *page, + unsigned int order) +{ + __destroy_compound_gigantic_page(page, order, true); +} + +#ifdef CONFIG_ARCH_HAS_GIGANTIC_PAGE static void destroy_compound_gigantic_page(struct page *page, unsigned int order) { @@ -1438,6 +1445,12 @@ static void remove_hugetlb_page(struct hstate *h, struct page *page, __remove_hugetlb_page(h, page, adjust_surplus, false); } +static void remove_hugetlb_page_for_demote(struct hstate *h, struct page *page, + bool adjust_surplus) +{ + __remove_hugetlb_page(h, page, adjust_surplus, true); +} + static void add_hugetlb_page(struct hstate *h, struct page *page, bool adjust_surplus) { @@ -1779,6 +1792,12 @@ static bool prep_compound_gigantic_page(struct page *page, unsigned int order) return __prep_compound_gigantic_page(page, order, false); } +static bool prep_compound_gigantic_page_for_demote(struct page *page, + unsigned int order) +{ + return __prep_compound_gigantic_page(page, order, true); +} + /* * PageHuge() only returns true for hugetlbfs pages, but not for normal or * transparent huge pages. See the PageTransHuge() documentation for more @@ -3302,9 +3321,54 @@ static int set_max_huge_pages(struct hstate *h, unsigned long count, int nid, return 0; } +static int demote_free_huge_page(struct hstate *h, struct page *page) +{ + int i, nid = page_to_nid(page); + struct hstate *target_hstate; + int rc = 0; + + target_hstate = size_to_hstate(PAGE_SIZE << h->demote_order); + + remove_hugetlb_page_for_demote(h, page, false); + spin_unlock_irq(&hugetlb_lock); + + rc = alloc_huge_page_vmemmap(h, page); + if (rc) { + /* Allocation of vmemmmap failed, we can not demote page */ + spin_lock_irq(&hugetlb_lock); + set_page_refcounted(page); + add_hugetlb_page(h, page, false); + return rc; + } + + /* + * Use destroy_compound_gigantic_page_for_demote for all huge page + * sizes as it will not ref count pages. + */ + destroy_compound_gigantic_page_for_demote(page, huge_page_order(h)); + + for (i = 0; i < pages_per_huge_page(h); + i += pages_per_huge_page(target_hstate)) { + if (hstate_is_gigantic(target_hstate)) + prep_compound_gigantic_page_for_demote(page + i, + target_hstate->order); + else + prep_compound_page(page + i, target_hstate->order); + set_page_private(page + i, 0); + set_page_refcounted(page + i); + prep_new_huge_page(target_hstate, page + i, nid); + put_page(page + i); + } + + spin_lock_irq(&hugetlb_lock); + return rc; +} + static int demote_pool_huge_page(struct hstate *h, nodemask_t *nodes_allowed) __must_hold(&hugetlb_lock) { + int nr_nodes, node; + struct page *page; int rc = 0; lockdep_assert_held(&hugetlb_lock); @@ -3313,9 +3377,15 @@ static int demote_pool_huge_page(struct hstate *h, nodemask_t *nodes_allowed) if (!h->demote_order) return rc; - /* - * TODO - demote fucntionality will be added in subsequent patch - */ + for_each_node_mask_to_free(h, nr_nodes, node, nodes_allowed) { + if (!list_empty(&h->hugepage_freelists[node])) { + page = list_entry(h->hugepage_freelists[node].next, + struct page, lru); + rc = !demote_free_huge_page(h, page); + break; + } + } + return rc; } @@ -3550,10 +3620,6 @@ static ssize_t demote_store(struct kobject *kobj, /* * Check for available pages to demote each time thorough the * loop as demote_pool_huge_page will drop hugetlb_lock. - * - * NOTE: demote_pool_huge_page does not yet drop hugetlb_lock - * but will when full demote functionality is added in a later - * patch. */ if (nid != NUMA_NO_NODE) nr_available = h->free_huge_pages_node[nid];
Demote page functionality will split a huge page into a number of huge pages of a smaller size. For example, on x86 a 1GB huge page can be demoted into 512 2M huge pages. Demotion is done 'in place' by simply splitting the huge page. Added '*_for_demote' wrappers for remove_hugetlb_page, destroy_compound_gigantic_page and prep_compound_gigantic_page for use by demote code. Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com> --- mm/hugetlb.c | 82 +++++++++++++++++++++++++++++++++++++++++++++++----- 1 file changed, 74 insertions(+), 8 deletions(-)