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Subject[PATCH 2/2] mm, memory_hotplug: remove timeout from __offline_memory
Date
From: Michal Hocko <mhocko@suse.com>

We have a hardcoded 120s timeout after which the memory offline fails
basically since the hot remove has been introduced. This is essentially
a policy implemented in the kernel. Moreover there is no way to adjust
the timeout and so we are sometimes facing memory offline failures if
the system is under a heavy memory pressure or very intensive CPU
workload on large machines.

It is not very clear what purpose the timeout actually serves. The
offline operation is interruptible by a signal so if userspace wants
some timeout based termination this can be done trivially by sending a
signal.

If there is a strong usecase to do this from the kernel then we should
do it properly and have a it tunable from the userspace with the timeout
disabled by default along with the explanation who uses it and for what
purporse.

Acked-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Michal Hocko <mhocko@suse.com>
---
mm/memory_hotplug.c | 10 +++-------
1 file changed, 3 insertions(+), 7 deletions(-)

diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index c9dcbe6d2ac6..b8a85c11360e 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -1593,9 +1593,9 @@ static void node_states_clear_node(int node, struct memory_notify *arg)
}

static int __ref __offline_pages(unsigned long start_pfn,
- unsigned long end_pfn, unsigned long timeout)
+ unsigned long end_pfn)
{
- unsigned long pfn, nr_pages, expire;
+ unsigned long pfn, nr_pages;
long offlined_pages;
int ret, node;
unsigned long flags;
@@ -1633,12 +1633,8 @@ static int __ref __offline_pages(unsigned long start_pfn,
goto failed_removal;

pfn = start_pfn;
- expire = jiffies + timeout;
repeat:
/* start memory hot removal */
- ret = -EBUSY;
- if (time_after(jiffies, expire))
- goto failed_removal;
ret = -EINTR;
if (signal_pending(current))
goto failed_removal;
@@ -1711,7 +1707,7 @@ static int __ref __offline_pages(unsigned long start_pfn,
/* Must be protected by mem_hotplug_begin() or a device_lock */
int offline_pages(unsigned long start_pfn, unsigned long nr_pages)
{
- return __offline_pages(start_pfn, start_pfn + nr_pages, 120 * HZ);
+ return __offline_pages(start_pfn, start_pfn + nr_pages);
}
#endif /* CONFIG_MEMORY_HOTREMOVE */

--
2.14.1
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