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SubjectRe: [PATCH 2/2] mm, memory_hotplug: remove timeout from __offline_memory
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On 09/04/2017 10:21 AM, Michal Hocko wrote:
> 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.
>
> Signed-off-by: Michal Hocko <mhocko@suse.com>

Makes sense to me.

Acked-by: Vlastimil Babka <vbabka@suse.cz>

> ---
> 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 */
>
>

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