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vmm: always try THP for VM RAM

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The kernel allows madvise on shared memory if
/sys/kernel/mm/transparent_hugepage/shmem_enabled is set.
Always try and configure THP via madvise when
the user requests THP be enabled.
If this fails, only a warning log is emitted and THP won't be enabled.

Signed-off-by: Champ-Goblem <cameron@northflank.com>
This commit is contained in:
Champ-Goblem 2026-02-06 17:13:07 +00:00 • committed by Rob Bradford
parent 2c2f5d2431
commit 1e0eba60af
1 changed files with 10 additions and 9 deletions
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19
vmm/src/memory_manager.rs
View file

@ -25,9 +25,7 @@ use devices::ioapic;
#[cfg(target_arch = "aarch64")]
use hypervisor::HypervisorVmError;
use libc::_SC_NPROCESSORS_ONLN;
#[cfg(all(target_arch = "x86_64", feature = "guest_debug"))]
use log::debug;
use log::{error, info, warn};
use log::{debug, error, info, warn};
use serde::{Deserialize, Serialize};
use thiserror::Error;
use tracer::trace_scoped;
@ -1490,17 +1488,20 @@ impl MemoryManager {
});
}
if region.file_offset().is_none() && thp {
info!(
"Anonymous mapping at 0x{:x} (size = 0x{:x})",
region.as_ptr() as u64,
size
);
info!(
"RAM region mapping at 0x{:x} (size = 0x{:x})",
region.as_ptr() as u64,
size
);
if thp && !hugepages {
// SAFETY: FFI call with correct arguments
let ret = unsafe { libc::madvise(region.as_ptr() as _, size, libc::MADV_HUGEPAGE) };
if ret != 0 {
let e = io::Error::last_os_error();
warn!("Failed to mark pages as THP eligible: {e}");
} else {
debug!("Successfully marked pages as THP eligible");
}
}