diff options
| author | Junaid Shahid <junaids@google.com> | 2021-10-20 04:06:27 +0300 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2021-10-22 12:19:28 +0300 |
| commit | 4dfe4f40d845cdca655b27bf207959855f3e2d62 (patch) | |
| tree | 552cf71e45bec2a7bf0ce07519e5d10b3e75f236 /Documentation/admin-guide | |
| parent | 540c7abe61cc5e81a3d17fe02bce94f6cbf9dce0 (diff) | |
| download | linux-4dfe4f40d845cdca655b27bf207959855f3e2d62.tar.xz | |
kvm: x86: mmu: Make NX huge page recovery period configurable
Currently, the NX huge page recovery thread wakes up every minute and
zaps 1/nx_huge_pages_recovery_ratio of the total number of split NX
huge pages at a time. This is intended to ensure that only a
relatively small number of pages get zapped at a time. But for very
large VMs (or more specifically, VMs with a large number of
executable pages), a period of 1 minute could still result in this
number being too high (unless the ratio is changed significantly,
but that can result in split pages lingering on for too long).
This change makes the period configurable instead of fixing it at
1 minute. Users of large VMs can then adjust the period and/or the
ratio to reduce the number of pages zapped at one time while still
maintaining the same overall duration for cycling through the
entire list. By default, KVM derives a period from the ratio such
that a page will remain on the list for 1 hour on average.
Signed-off-by: Junaid Shahid <junaids@google.com>
Message-Id: <20211020010627.305925-1-junaids@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'Documentation/admin-guide')
| -rw-r--r-- | Documentation/admin-guide/kernel-parameters.txt | 9 |
1 files changed, 8 insertions, 1 deletions
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 91ba391f9b32..f780844c8390 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -2353,7 +2353,14 @@ [KVM] Controls how many 4KiB pages are periodically zapped back to huge pages. 0 disables the recovery, otherwise if the value is N KVM will zap 1/Nth of the 4KiB pages every - minute. The default is 60. + period (see below). The default is 60. + + kvm.nx_huge_pages_recovery_period_ms= + [KVM] Controls the time period at which KVM zaps 4KiB pages + back to huge pages. If the value is a non-zero N, KVM will + zap a portion (see ratio above) of the pages every N msecs. + If the value is 0 (the default), KVM will pick a period based + on the ratio, such that a page is zapped after 1 hour on average. kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM. Default is 1 (enabled) |