The Russian-Chinese encounter in Harbin, Manchuria, 1898-1932

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A Frugal Approach to Reduce RCU Grace Period Overhead

Grace period computation is a core part of the Read-Copy-Update (RCU) synchronization technique that determines the safe time to reclaim the deferred objects' memory. We first show that the eager grace period computation employed in the Linux kernel is appropriate only for enterprise workloads such as web and database servers where a large amount of reclaimable memory awaits the completion of a grace period. However, such memory is negligible in High-Performance Computing (HPC) and mostly idling environments due to limited OS kernel activity. Hence an eager approach is not only futile but also detrimental as the CPU cycles consumed to compute a grace period leads to jitter in HPC and frequent CPU wake-ups in idle environments. We design frugal grace periods, an economical grace period computation for non-enterprise environments that consume fewer CPU cycles. In addition, we reduce the number of grace periods either by using heuristics or by letting the memory allocator to explicitly request for a grace period only when it is running out of free objects. Our implementation in the Linux kernel reduces the number of grace periods by 68% to 99%, reduces the CPU time consumed by grace periods by 39% to 99%, improves the throughput by up to 28% for NAS parallel benchmarks and increases the CPU time spent in low power states by 2.4x when the system is idle

Smoked cannabis for chronic neuropathic pain: a randomized controlled trial

Background: Chronic neuropathic pain affects 1%–2 % of the adult population and is often refractory to standard pharmacologic treatment. Patients with chronic pain have reported using smoked cannabis to relieve pain, improve sleep and improve mood. Methods: Adults with post-traumatic or postsurgical neuropathic pain were randomly assigned to receive cannabis at four potencies (0%, 2.5%, 6 % and 9.4 % tetrahydrocannabinol) over four 14-day periods in a crossover trial. Participants inhaled a single 25-mg dose through a pipe three times daily for the first five days in each cycle, followed by a nine-day washout period. Daily average pain intensity was measured using an 11-point numeric rating scale. We recorded effects on mood, sleep and quality of life, as well as adverse events