Re: [PATCH v6 2/6] mm/memplicy: add page allocation function for MPOL_PREFERRED_MANY policy
From: Michal Hocko <mhocko@suse.com>
Date: 2021-07-28 12:42:33
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On Mon 12-07-21 16:09:30, Feng Tang wrote:
The semantics of MPOL_PREFERRED_MANY is similar to MPOL_PREFERRED, that it will first try to allocate memory from the preferred node(s), and fallback to all nodes in system when first try fails. Add a dedicated function for it just like 'interleave' policy. Link: https://lore.kernel.org/r/20200630212517.308045-9-ben.widawsky@intel.com (local) Suggested-by: Michal Hocko <mhocko@suse.com> Co-developed-by: Ben Widawsky <redacted> Signed-off-by: Ben Widawsky <redacted> Signed-off-by: Feng Tang <redacted>
It would be better to squash this together with the actual user of the function added by the next patch.
quoted hunk ↗ jump to hunk
--- mm/mempolicy.c | 19 +++++++++++++++++++ 1 file changed, 19 insertions(+)diff --git a/mm/mempolicy.c b/mm/mempolicy.c index 17b5800b7dcc..d17bf018efcc 100644 --- a/mm/mempolicy.c +++ b/mm/mempolicy.c@@ -2153,6 +2153,25 @@ static struct page *alloc_page_interleave(gfp_t gfp, unsigned order, return page; } +static struct page *alloc_page_preferred_many(gfp_t gfp, unsigned int order, + struct mempolicy *pol)
We likely want a node parameter to know which one we want to start with for locality. Callers should use policy_node for that.
+{
+ struct page *page;
+
+ /*
+ * This is a two pass approach. The first pass will only try the
+ * preferred nodes but skip the direct reclaim and allow the
+ * allocation to fail, while the second pass will try all the
+ * nodes in system.
+ */
+ page = __alloc_pages(((gfp | __GFP_NOWARN) & ~__GFP_DIRECT_RECLAIM),
+ order, first_node(pol->nodes), &pol->nodes);Although most users will likely have some form of GFP_*USER* here and clearing __GFP_DIRECT_RECLAIM will put all other reclaim modifiers out of game I think it would be better to explicitly disable some of them to prevent from surprises. E.g. any potential __GFP_NOFAIL would be more than surprising here. We do not have any (hopefully) but this should be pretty cheap to exclude as we already have to modify already. preferred_gfp = gfp | __GFP_NOWARN; preferred_gfp &= ~(__GFP_DIRECT_RECLAIM | __GFP_NOFAIL)
+ if (!page) + page = __alloc_pages(gfp, order, numa_node_id(), NULL); + + return page; +} + /** * alloc_pages_vma - Allocate a page for a VMA. * @gfp: GFP flags. -- 2.7.4
-- Michal Hocko SUSE Labs