linux-kernel - [PATCH v2] memcg: page_alloc: skip bulk allocator for __GFP

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Message-Id: <20211014151607.2171970-1-shakeelb@google.com>
Date:   Thu, 14 Oct 2021 08:16:07 -0700
From:   Shakeel Butt <shakeelb@...gle.com>
To:     Johannes Weiner <hannes@...xchg.org>,
        Michal Hocko <mhocko@...nel.org>,
        Mel Gorman <mgorman@...hsingularity.net>
Cc:     Uladzislau Rezki <urezki@...il.com>,
        Vasily Averin <vvs@...tuozzo.com>,
        Roman Gushchin <guro@...com>,
        Matthew Wilcox <willy@...radead.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        cgroups@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, Shakeel Butt <shakeelb@...gle.com>
Subject: [PATCH v2] memcg: page_alloc: skip bulk allocator for __GFP_ACCOUNT

The commit 5c1f4e690eec ("mm/vmalloc: switch to bulk allocator in
__vmalloc_area_node()") switched to bulk page allocator for order 0
allocation backing vmalloc. However bulk page allocator does not support
__GFP_ACCOUNT allocations and there are several users of
kvmalloc(__GFP_ACCOUNT).

For now make __GFP_ACCOUNT allocations bypass bulk page allocator. In
future if there is workload that can be significantly improved with the
bulk page allocator with __GFP_ACCCOUNT support, we can revisit the
decision.

Fixes: 5c1f4e690eec ("mm/vmalloc: switch to bulk allocator in __vmalloc_area_node()")
Signed-off-by: Shakeel Butt <shakeelb@...gle.com>
---
Changes since v1:
- do fallback allocation instead of failure, suggested by Michal Hocko.
- Added memcg_kmem_enabled() check, corrected by Vasily Averin

 mm/page_alloc.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 668edb16446a..9ca871dc8602 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -5230,6 +5230,10 @@ unsigned long __alloc_pages_bulk(gfp_t gfp, int preferred_nid,
 	if (unlikely(page_array && nr_pages - nr_populated == 0))
 		goto out;
 
+	/* Bulk allocator does not support memcg accounting. */
+	if (memcg_kmem_enabled() && (gfp & __GFP_ACCOUNT))
+		goto failed;
+
 	/* Use the single page allocator for one page. */
 	if (nr_pages - nr_populated == 1)
 		goto failed;
-- 
2.33.0.882.g93a45727a2-goog