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Diffstat (limited to 'Documentation/vm')
| -rw-r--r-- | Documentation/vm/transhuge.txt | 17 |
1 files changed, 17 insertions, 0 deletions
diff --git a/Documentation/vm/transhuge.txt b/Documentation/vm/transhuge.txt index 0dc8632aa01e..d9cb65cf5cfd 100644 --- a/Documentation/vm/transhuge.txt +++ b/Documentation/vm/transhuge.txt @@ -113,9 +113,26 @@ guaranteed, but it may be more likely in case the allocation is for a MADV_HUGEPAGE region. echo always >/sys/kernel/mm/transparent_hugepage/defrag +echo defer >/sys/kernel/mm/transparent_hugepage/defrag echo madvise >/sys/kernel/mm/transparent_hugepage/defrag echo never >/sys/kernel/mm/transparent_hugepage/defrag +"always" means that an application requesting THP will stall on allocation +failure and directly reclaim pages and compact memory in an effort to +allocate a THP immediately. This may be desirable for virtual machines +that benefit heavily from THP use and are willing to delay the VM start +to utilise them. + +"defer" means that an application will wake kswapd in the background +to reclaim pages and wake kcompact to compact memory so that THP is +available in the near future. It's the responsibility of khugepaged +to then install the THP pages later. + +"madvise" will enter direct reclaim like "always" but only for regions +that are have used madvise(MADV_HUGEPAGE). This is the default behaviour. + +"never" should be self-explanatory. + By default kernel tries to use huge zero page on read page fault. It's possible to disable huge zero page by writing 0 or enable it back by writing 1: |