diff options
Diffstat (limited to 'Documentation/admin-guide/sysctl/vm.rst')
| -rw-r--r-- | Documentation/admin-guide/sysctl/vm.rst | 42 |
1 files changed, 22 insertions, 20 deletions
diff --git a/Documentation/admin-guide/sysctl/vm.rst b/Documentation/admin-guide/sysctl/vm.rst index 586cd4b86428..8387ad0b0b83 100644 --- a/Documentation/admin-guide/sysctl/vm.rst +++ b/Documentation/admin-guide/sysctl/vm.rst @@ -64,7 +64,7 @@ Currently, these files are in /proc/sys/vm: - overcommit_ratio - page-cluster - panic_on_oom -- percpu_pagelist_fraction +- percpu_pagelist_high_fraction - stat_interval - stat_refresh - numa_stat @@ -790,22 +790,24 @@ panic_on_oom=2+kdump gives you very strong tool to investigate why oom happens. You can get snapshot. -percpu_pagelist_fraction -======================== +percpu_pagelist_high_fraction +============================= -This is the fraction of pages at most (high mark pcp->high) in each zone that -are allocated for each per cpu page list. The min value for this is 8. It -means that we don't allow more than 1/8th of pages in each zone to be -allocated in any single per_cpu_pagelist. This entry only changes the value -of hot per cpu pagelists. User can specify a number like 100 to allocate -1/100th of each zone to each per cpu page list. +This is the fraction of pages in each zone that are can be stored to +per-cpu page lists. It is an upper boundary that is divided depending +on the number of online CPUs. The min value for this is 8 which means +that we do not allow more than 1/8th of pages in each zone to be stored +on per-cpu page lists. This entry only changes the value of hot per-cpu +page lists. A user can specify a number like 100 to allocate 1/100th of +each zone between per-cpu lists. -The batch value of each per cpu pagelist is also updated as a result. It is -set to pcp->high/4. The upper limit of batch is (PAGE_SHIFT * 8) +The batch value of each per-cpu page list remains the same regardless of +the value of the high fraction so allocation latencies are unaffected. -The initial value is zero. Kernel does not use this value at boot time to set -the high water marks for each per cpu page list. If the user writes '0' to this -sysctl, it will revert to this default behavior. +The initial value is zero. Kernel uses this value to set the high pcp->high +mark based on the low watermark for the zone and the number of local +online CPUs. If the user writes '0' to this sysctl, it will revert to +this default behavior. stat_interval @@ -936,12 +938,12 @@ allocations, THP and hugetlbfs pages. To make it sensible with respect to the watermark_scale_factor parameter, the unit is in fractions of 10,000. The default value of -15,000 on !DISCONTIGMEM configurations means that up to 150% of the high -watermark will be reclaimed in the event of a pageblock being mixed due -to fragmentation. The level of reclaim is determined by the number of -fragmentation events that occurred in the recent past. If this value is -smaller than a pageblock then a pageblocks worth of pages will be reclaimed -(e.g. 2MB on 64-bit x86). A boost factor of 0 will disable the feature. +15,000 means that up to 150% of the high watermark will be reclaimed in the +event of a pageblock being mixed due to fragmentation. The level of reclaim +is determined by the number of fragmentation events that occurred in the +recent past. If this value is smaller than a pageblock then a pageblocks +worth of pages will be reclaimed (e.g. 2MB on 64-bit x86). A boost factor +of 0 will disable the feature. watermark_scale_factor |