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Patch series "mm/memcg: Address PREEMPT_RT problems instead of disabling it", v5. This series aims to address the memcg related problem on PREEMPT_RT. I tested them on CONFIG_PREEMPT and CONFIG_PREEMPT_RT with the tools/testing/selftests/cgroup/* tests and I haven't observed any regressions (other than the lockdep report that is already there). This patch (of 6): The optimisation is based on a micro benchmark where local_irq_save() is more expensive than a preempt_disable(). There is no evidence that it is visible in a real-world workload and there are CPUs where the opposite is true (local_irq_save() is cheaper than preempt_disable()). Based on micro benchmarks, the optimisation makes sense on PREEMPT_NONE where preempt_disable() is optimized away. There is no improvement with PREEMPT_DYNAMIC since the preemption counter is always available. The optimization makes also the PREEMPT_RT integration more complicated since most of the assumption are not true on PREEMPT_RT. Revert the optimisation since it complicates the PREEMPT_RT integration and the improvement is hardly visible. [bigeasy@linutronix.de: patch body around Michal's diff] Link: https://lkml.kernel.org/r/20220226204144.1008339-1-bigeasy@linutronix.de Link: https://lore.kernel.org/all/YgOGkXXCrD%2F1k+p4@dhcp22.suse.cz Link: https://lkml.kernel.org/r/YdX+INO9gQje6d0S@linutronix.de Link: https://lkml.kernel.org/r/20220226204144.1008339-2-bigeasy@linutronix.de Signed-off-by: Michal Hocko <mhocko@suse.com> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Acked-by: Roman Gushchin <guro@fb.com> Acked-by: Johannes Weiner <hannes@cmpxchg.org> Reviewed-by: Shakeel Butt <shakeelb@google.com> Acked-by: Michal Hocko <mhocko@suse.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Vladimir Davydov <vdavydov.dev@gmail.com> Cc: Waiman Long <longman@redhat.com> Cc: kernel test robot <oliver.sang@intel.com> Cc: Michal Hocko <mhocko@kernel.org> Cc: Michal Koutný <mkoutny@suse.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
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https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.