linux-kernel - [PATCH v3 07/20] vmw_balloon: treat all refused pages equally

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Message-ID: <20180926191336.101885-8-namit@vmware.com>
Date:   Wed, 26 Sep 2018 12:13:23 -0700
From:   Nadav Amit <namit@...are.com>
To:     Arnd Bergmann <arnd@...db.de>, <gregkh@...uxfoundation.org>
CC:     Xavier Deguillard <xdeguillard@...are.com>,
        <linux-kernel@...r.kernel.org>, Nadav Amit <namit@...are.com>
Subject: [PATCH v3 07/20] vmw_balloon: treat all refused pages equally

Currently, when the hypervisor rejects a page during lock operation, the
VM treats pages differently according to the error-code: in certain
cases the page is immediately freed, and in others it is put on a
rejection list and only freed later.

The behavior does not make too much sense. If the page is freed
immediately it is very likely to be used again in the next batch of
allocations, and be rejected again.

In addition, for support of compaction and OOM notifiers, we wish to
separate the logic that communicates with the hypervisor (as well as
analyzes the status of each page) from the logic that allocates or free
pages.

Treat all errors the same way, queuing the pages on the refuse list.
Move to the next allocation size (4k) when too many pages are refused.
Free the refused pages when moving to the next size to avoid situations
in which too much memory is waiting to be freed on the refused list.

Reviewed-by: Xavier Deguillard <xdeguillard@...are.com>
Signed-off-by: Nadav Amit <namit@...are.com>
---
 drivers/misc/vmw_balloon.c | 52 +++++++++++++++++++++-----------------
 1 file changed, 29 insertions(+), 23 deletions(-)

diff --git a/drivers/misc/vmw_balloon.c b/drivers/misc/vmw_balloon.c
index 96dde120bbd5..4e067d269706 100644
--- a/drivers/misc/vmw_balloon.c
+++ b/drivers/misc/vmw_balloon.c
@@ -543,29 +543,13 @@ static int vmballoon_lock(struct vmballoon *b, unsigned int num_pages,
 		/* Error occurred */
 		STATS_INC(b->stats.refused_alloc[is_2m_pages]);
 
-		switch (status) {
-		case VMW_BALLOON_ERROR_PPN_PINNED:
-		case VMW_BALLOON_ERROR_PPN_INVALID:
-			/*
-			 * Place page on the list of non-balloonable pages
-			 * and retry allocation, unless we already accumulated
-			 * too many of them, in which case take a breather.
-			 */
-			if (page_size->n_refused_pages
-					< VMW_BALLOON_MAX_REFUSED) {
-				list_add(&p->lru, &page_size->refused_pages);
-				page_size->n_refused_pages++;
-				break;
-			}
-			/* Fallthrough */
-		case VMW_BALLOON_ERROR_RESET:
-		case VMW_BALLOON_ERROR_PPN_NOTNEEDED:
-			vmballoon_free_page(p, is_2m_pages);
-			break;
-		default:
-			/* This should never happen */
-			WARN_ON_ONCE(true);
-		}
+		/*
+		 * Place page on the list of non-balloonable pages
+		 * and retry allocation, unless we already accumulated
+		 * too many of them, in which case take a breather.
+		 */
+		list_add(&p->lru, &page_size->refused_pages);
+		page_size->n_refused_pages++;
 	}
 
 	return batch_status == VMW_BALLOON_SUCCESS ? 0 : -EIO;
@@ -712,9 +696,31 @@ static void vmballoon_inflate(struct vmballoon *b)
 
 		vmballoon_add_page(b, num_pages++, page);
 		if (num_pages == b->batch_max_pages) {
+			struct vmballoon_page_size *page_size =
+					&b->page_sizes[is_2m_pages];
+
 			error = vmballoon_lock(b, num_pages, is_2m_pages);
 
 			num_pages = 0;
+
+			/*
+			 * Stop allocating this page size if we already
+			 * accumulated too many pages that the hypervisor
+			 * refused.
+			 */
+			if (page_size->n_refused_pages >=
+			    VMW_BALLOON_MAX_REFUSED) {
+				if (!is_2m_pages)
+					break;
+
+				/*
+				 * Release the refused pages as we move to 4k
+				 * pages.
+				 */
+				vmballoon_release_refused_pages(b, true);
+				is_2m_pages = true;
+			}
+
 			if (error)
 				break;
 		}
-- 
2.17.1