diff options
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/sysctl/vm.txt | 11 | ||||
| -rw-r--r-- | Documentation/vm/balance | 18 |
2 files changed, 15 insertions, 14 deletions
diff --git a/Documentation/sysctl/vm.txt b/Documentation/sysctl/vm.txt index 6fab2dcbb4d..0ea5adbc5b1 100644 --- a/Documentation/sysctl/vm.txt +++ b/Documentation/sysctl/vm.txt @@ -233,8 +233,8 @@ These protections are added to score to judge whether this zone should be used for page allocation or should be reclaimed. In this example, if normal pages (index=2) are required to this DMA zone and -pages_high is used for watermark, the kernel judges this zone should not be -used because pages_free(1355) is smaller than watermark + protection[2] +watermark[WMARK_HIGH] is used for watermark, the kernel judges this zone should +not be used because pages_free(1355) is smaller than watermark + protection[2] (4 + 2004 = 2008). If this protection value is 0, this zone would be used for normal page requirement. If requirement is DMA zone(index=0), protection[0] (=0) is used. @@ -280,9 +280,10 @@ The default value is 65536. min_free_kbytes: This is used to force the Linux VM to keep a minimum number -of kilobytes free. The VM uses this number to compute a pages_min -value for each lowmem zone in the system. Each lowmem zone gets -a number of reserved free pages based proportionally on its size. +of kilobytes free. The VM uses this number to compute a +watermark[WMARK_MIN] value for each lowmem zone in the system. +Each lowmem zone gets a number of reserved free pages based +proportionally on its size. Some minimal amount of memory is needed to satisfy PF_MEMALLOC allocations; if you set this to lower than 1024KB, your system will diff --git a/Documentation/vm/balance b/Documentation/vm/balance index bd3d31bc491..c46e68cf934 100644 --- a/Documentation/vm/balance +++ b/Documentation/vm/balance @@ -75,15 +75,15 @@ Page stealing from process memory and shm is done if stealing the page would alleviate memory pressure on any zone in the page's node that has fallen below its watermark. -pages_min/pages_low/pages_high/low_on_memory/zone_wake_kswapd: These are -per-zone fields, used to determine when a zone needs to be balanced. When -the number of pages falls below pages_min, the hysteric field low_on_memory -gets set. This stays set till the number of free pages becomes pages_high. -When low_on_memory is set, page allocation requests will try to free some -pages in the zone (providing GFP_WAIT is set in the request). Orthogonal -to this, is the decision to poke kswapd to free some zone pages. That -decision is not hysteresis based, and is done when the number of free -pages is below pages_low; in which case zone_wake_kswapd is also set. +watemark[WMARK_MIN/WMARK_LOW/WMARK_HIGH]/low_on_memory/zone_wake_kswapd: These +are per-zone fields, used to determine when a zone needs to be balanced. When +the number of pages falls below watermark[WMARK_MIN], the hysteric field +low_on_memory gets set. This stays set till the number of free pages becomes +watermark[WMARK_HIGH]. When low_on_memory is set, page allocation requests will +try to free some pages in the zone (providing GFP_WAIT is set in the request). +Orthogonal to this, is the decision to poke kswapd to free some zone pages. +That decision is not hysteresis based, and is done when the number of free +pages is below watermark[WMARK_LOW]; in which case zone_wake_kswapd is also set. (Good) Ideas that I have heard: |