On Mon, Oct 16, 2023 at 01:29:59PM +0800, Huang Ying wrote: > The page allocation performance requirements of different workloads > are usually different. So, we need to tune PCP (per-CPU pageset) high > to optimize the workload page allocation performance. Now, we have a > system wide sysctl knob (percpu_pagelist_high_fraction) to tune PCP > high by hand. But, it's hard to find out the best value by hand. And > one global configuration may not work best for the different workloads > that run on the same system. One solution to these issues is to tune > PCP high of each CPU automatically. > > This patch adds the framework for PCP high auto-tuning. With it, > pcp->high of each CPU will be changed automatically by tuning > algorithm at runtime. The minimal high (pcp->high_min) is the > original PCP high value calculated based on the low watermark pages. > While the maximal high (pcp->high_max) is the PCP high value when > percpu_pagelist_high_fraction sysctl knob is set to > MIN_PERCPU_PAGELIST_HIGH_FRACTION. That is, the maximal pcp->high > that can be set via sysctl knob by hand. > > It's possible that PCP high auto-tuning doesn't work well for some > workloads. So, when PCP high is tuned by hand via the sysctl knob, > the auto-tuning will be disabled. The PCP high set by hand will be > used instead. > > This patch only adds the framework, so pcp->high will be set to > pcp->high_min (original default) always. We will add actual > auto-tuning algorithm in the following patches in the series. > > Signed-off-by: "Huang, Ying" <ying.huang@xxxxxxxxx> Acked-by: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx> -- Mel Gorman SUSE Labs
