From 2ed53c0d6cc99fc712f7c037e41d9ec4eb8d6b08 Mon Sep 17 00:00:00 2001 From: Lan Tianyu Date: Tue, 26 Aug 2014 15:43:45 +0800 Subject: [PATCH] x86/smpboot: Speed up suspend/resume by avoiding 100ms sleep for CPU offline during S3 With certain kernel configurations, CPU offline consumes more than 100ms during S3. It's a timing related issue: native_cpu_die() would occasionally fall into a 100ms sleep when the CPU idle loop thread marked the CPU state to DEAD too slowly. What native_cpu_die() does is that it polls the CPU state and waits for 100ms if CPU state hasn't been marked to DEAD. The 100ms sleep doesn't make sense and is purely historic. To avoid such long sleeping, this patch adds a 'struct completion' to each CPU, waits for the completion in native_cpu_die() and wakes up the completion when the CPU state is marked to DEAD. Tested on an Intel Xeon server with 48 cores, Ivybridge and on Haswell laptops. The CPU offlining cost on these machines is reduced from more than 100ms to less than 5ms. The system suspend time is reduced by 2.3s on the servers. Borislav and Prarit also helped to test the patch on an AMD machine and a few systems of various sizes and configurations (multi-socket, single-socket, no hyper threading, etc.). No issues were seen. Tested-by: Prarit Bhargava Signed-off-by: Lan Tianyu Acked-by: Borislav Petkov Cc: Peter Zijlstra Cc: srostedt@redhat.com Cc: toshi.kani@hp.com Cc: imammedo@redhat.com Cc: Linus Torvalds Link: http://lkml.kernel.org/r/1409039025-32310-1-git-send-email-tianyu.lan@intel.com [ Improved a few minor details in the code, cleaned up the changelog. ] Signed-off-by: Ingo Molnar --- Reading git-format-patch failed