From 90b41691b9881376fe784e13b5766ec3676fdb55 Mon Sep 17 00:00:00 2001 From: Huang Ying Date: Mon, 16 Oct 2023 13:29:59 +0800 Subject: mm: add framework for PCP high auto-tuning 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. Link: https://lkml.kernel.org/r/20231016053002.756205-7-ying.huang@intel.com Signed-off-by: "Huang, Ying" Acked-by: Mel Gorman Cc: Vlastimil Babka Cc: David Hildenbrand Cc: Johannes Weiner Cc: Dave Hansen Cc: Michal Hocko Cc: Pavel Tatashin Cc: Matthew Wilcox Cc: Christoph Lameter Cc: Arjan van de Ven Cc: Sudeep Holla Signed-off-by: Andrew Morton --- include/linux/mmzone.h | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) (limited to 'include/linux') diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h index e6cc2238c65f..775abc899e80 100644 --- a/include/linux/mmzone.h +++ b/include/linux/mmzone.h @@ -693,6 +693,8 @@ struct per_cpu_pages { spinlock_t lock; /* Protects lists field */ int count; /* number of pages in the list */ int high; /* high watermark, emptying needed */ + int high_min; /* min high watermark */ + int high_max; /* max high watermark */ int batch; /* chunk size for buddy add/remove */ u8 flags; /* protected by pcp->lock */ u8 alloc_factor; /* batch scaling factor during allocate */ @@ -852,7 +854,8 @@ struct zone { * the high and batch values are copied to individual pagesets for * faster access */ - int pageset_high; + int pageset_high_min; + int pageset_high_max; int pageset_batch; #ifndef CONFIG_SPARSEMEM -- cgit v1.2.3