Author: gallatin Date: Mon May 7 15:24:03 2018 New Revision: 333325 URL: https://svnweb.freebsd.org/changeset/base/333325
Log: Boost thread priority while changing CPU frequency Boost the priority of user-space threads when they set their affinity to a core to adjust its frequency. This avoids a situation where a CPU bound kernel thread with the same affinity is running on a down-clocked core, and will "block" powerd from up-clocking the core until the kernel thread yields. This can lead to poor perfomance, and to things potentially getting stuck on Giant. Reviewed by: kib (imp reviewed earlier version) Sponsored by: Netflix Differential Revision: https://reviews.freebsd.org/D15246 Modified: head/sys/kern/kern_cpu.c Modified: head/sys/kern/kern_cpu.c ============================================================================== --- head/sys/kern/kern_cpu.c Mon May 7 15:07:28 2018 (r333324) +++ head/sys/kern/kern_cpu.c Mon May 7 15:24:03 2018 (r333325) @@ -245,6 +245,7 @@ cf_set_method(device_t dev, const struct cf_level *lev struct cf_saved_freq *saved_freq, *curr_freq; struct pcpu *pc; int error, i; + u_char pri; sc = device_get_softc(dev); error = 0; @@ -333,6 +334,8 @@ cf_set_method(device_t dev, const struct cf_level *lev /* Bind to the target CPU before switching. */ pc = cpu_get_pcpu(set->dev); thread_lock(curthread); + pri = curthread->td_priority; + sched_prio(curthread, PRI_MIN); sched_bind(curthread, pc->pc_cpuid); thread_unlock(curthread); CF_DEBUG("setting abs freq %d on %s (cpu %d)\n", set->freq, @@ -340,6 +343,7 @@ cf_set_method(device_t dev, const struct cf_level *lev error = CPUFREQ_DRV_SET(set->dev, set); thread_lock(curthread); sched_unbind(curthread); + sched_prio(curthread, pri); thread_unlock(curthread); if (error) { goto out; @@ -357,6 +361,8 @@ cf_set_method(device_t dev, const struct cf_level *lev /* Bind to the target CPU before switching. */ pc = cpu_get_pcpu(set->dev); thread_lock(curthread); + pri = curthread->td_priority; + sched_prio(curthread, PRI_MIN); sched_bind(curthread, pc->pc_cpuid); thread_unlock(curthread); CF_DEBUG("setting rel freq %d on %s (cpu %d)\n", set->freq, @@ -364,6 +370,7 @@ cf_set_method(device_t dev, const struct cf_level *lev error = CPUFREQ_DRV_SET(set->dev, set); thread_lock(curthread); sched_unbind(curthread); + sched_prio(curthread, pri); thread_unlock(curthread); if (error) { /* XXX Back out any successful setting? */ _______________________________________________ svn-src-head@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/svn-src-head To unsubscribe, send any mail to "svn-src-head-unsubscr...@freebsd.org"
