linux-kernel - [PATCH v1 4/5] virtio-mem: set the timeout for offline_and_remove

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Message-Id: <20230627112220.229240-5-david@redhat.com>
Date:   Tue, 27 Jun 2023 13:22:19 +0200
From:   David Hildenbrand <david@...hat.com>
To:     linux-kernel@...r.kernel.org
Cc:     linux-mm@...ck.org, virtualization@...ts.linux-foundation.org,
        David Hildenbrand <david@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        John Hubbard <jhubbard@...dia.com>,
        Oscar Salvador <osalvador@...e.de>,
        Michal Hocko <mhocko@...e.com>,
        Jason Wang <jasowang@...hat.com>,
        Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
Subject: [PATCH v1 4/5] virtio-mem: set the timeout for offline_and_remove_memory() to 10 seconds

Currently we use the default (30 seconds), let's reduce it to 10
seconds. In BBM, we barely deal with blocks larger than 1/2 GiB, and
after 10 seconds it's most probably best to give up on that memory block
and try another one (or retry this one later).

In the common fake-offline case where we effectively fake-offline memory
using alloc_contig_range() first (SBM or BBM with bbm_safe_unplug=on),
we expect offline_and_remove_memory() to be blazingly fast and never take
anywhere close to 10seconds -- so this should only affect BBM with
bbm_safe_unplug=off.

While at it, update the parameter description and the relationship to
unmovable pages.

Signed-off-by: David Hildenbrand <david@...hat.com>
---
 drivers/virtio/virtio_mem.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/virtio/virtio_mem.c b/drivers/virtio/virtio_mem.c
index f8792223f1db..7468b4a907e3 100644
--- a/drivers/virtio/virtio_mem.c
+++ b/drivers/virtio/virtio_mem.c
@@ -41,7 +41,7 @@ MODULE_PARM_DESC(bbm_block_size,
 static bool bbm_safe_unplug = true;
 module_param(bbm_safe_unplug, bool, 0444);
 MODULE_PARM_DESC(bbm_safe_unplug,
-	     "Use a safe unplug mechanism in BBM, avoiding long/endless loops");
+	     "Use a safe/fast unplug mechanism in BBM, failing faster on unmovable pages");
 
 /*
  * virtio-mem currently supports the following modes of operation:
@@ -738,7 +738,7 @@ static int virtio_mem_offline_and_remove_memory(struct virtio_mem *vm,
 		"offlining and removing memory: 0x%llx - 0x%llx\n", addr,
 		addr + size - 1);
 
-	rc = offline_and_remove_memory(addr, size, 0);
+	rc = offline_and_remove_memory(addr, size, 10 * MSEC_PER_SEC);
 	if (!rc) {
 		atomic64_sub(size, &vm->offline_size);
 		/*
-- 
2.40.1