mmap: try THP via madvise

src/guest_memory.rs

@@ -159,6 +159,15 @@ impl FileOffset {
     }
 }
 
+/// Configurations options usable for Guest Memory
+#[derive(Copy, Clone, Debug, Default, Eq, PartialEq, Ord, PartialOrd)]
+pub struct GuestMemoryOptions {
+    /// Use huge pages to back guest memory
+    pub huge_page: bool,
+    /// Use transparent huge pages to back guest memory
+    pub transparent_huge_page: bool,
+}
+
 /// Represents a continuous region of guest physical memory.
 #[allow(clippy::len_without_is_empty)]
 pub trait GuestMemoryRegion: Bytes<MemoryRegionAddress, E = Error> {

src/mmap.rs

@@ -22,7 +22,7 @@ use std::sync::Arc;
 
 use crate::address::Address;
 use crate::guest_memory::{
-    self, FileOffset, GuestAddress, GuestMemory, GuestMemoryRegion, GuestUsize, MemoryRegionAddress,
+    self, FileOffset, GuestAddress, GuestMemory, GuestMemoryOptions, GuestMemoryRegion, GuestUsize, MemoryRegionAddress,
 };
 use crate::volatile_memory::{VolatileMemory, VolatileSlice};
 use crate::Bytes;
@@ -391,6 +391,7 @@ impl GuestMemoryRegion for GuestRegionMmap {
 /// virtual address space of the calling process.
 #[derive(Clone, Debug, Default)]
 pub struct GuestMemoryMmap {
+    options: GuestMemoryOptions,
     regions: Vec<Arc<GuestRegionMmap>>,
 }
 
@@ -416,6 +417,7 @@ impl GuestMemoryMmap {
         A: Borrow<(GuestAddress, usize, Option<FileOffset>)>,
         T: IntoIterator<Item = A>,
     {
+        let options = GuestMemoryOptions {huge_page : false, transparent_huge_page : false};
         Self::from_regions(
             ranges
                 .into_iter()
@@ -424,9 +426,9 @@ impl GuestMemoryMmap {
                     let size = x.borrow().1;
 
                     if let Some(ref f_off) = x.borrow().2 {
-                        MmapRegion::from_file(f_off.clone(), size)
+                        MmapRegion::from_file(f_off.clone(), size, options)
                     } else {
-                        MmapRegion::new(size)
+                        MmapRegion::new(size, options)
                     }
                     .map_err(Error::MmapRegion)
                     .and_then(|r| GuestRegionMmap::new(r, guest_base))
@@ -476,7 +478,7 @@ impl GuestMemoryMmap {
             }
         }
 
-        Ok(Self { regions })
+        Ok(Self { regions, options: GuestMemoryOptions {huge_page : false, transparent_huge_page : false} })
     }
 
     /// Insert a region into the `GuestMemoryMmap` object and return a new `GuestMemoryMmap`.
@@ -509,7 +511,7 @@ impl GuestMemoryMmap {
             if self.regions.get(region_index).unwrap().size() as GuestUsize == size {
                 let mut regions = self.regions.clone();
                 let region = regions.remove(region_index);
-                return Ok((Self { regions }, region));
+                return Ok((Self { regions, options: GuestMemoryOptions {huge_page : false, transparent_huge_page : false} }, region));
             }
         }
 

src/mmap_unix.rs

@@ -20,6 +20,7 @@ use std::result;
 use libc;
 
 use crate::guest_memory::FileOffset;
+use crate::guest_memory::GuestMemoryOptions;
 use crate::mmap::{check_file_offset, AsSlice};
 use crate::volatile_memory::{self, compute_offset, VolatileMemory, VolatileSlice};
 
@@ -93,12 +94,13 @@ impl MmapRegion {
     ///
     /// # Arguments
     /// * `size` - The size of the memory region in bytes.
-    pub fn new(size: usize) -> Result<Self> {
+    pub fn new(size: usize, options: GuestMemoryOptions) -> Result<Self> {
         Self::build(
             None,
             size,
             libc::PROT_READ | libc::PROT_WRITE,
             libc::MAP_ANONYMOUS | libc::MAP_NORESERVE | libc::MAP_PRIVATE,
+            options
         )
     }
 
@@ -108,12 +110,13 @@ impl MmapRegion {
     /// * `file_offset` - The mapping will be created at offset `file_offset.start` in the file
     ///                   referred to by `file_offset.file`.
     /// * `size` - The size of the memory region in bytes.
-    pub fn from_file(file_offset: FileOffset, size: usize) -> Result<Self> {
+    pub fn from_file(file_offset: FileOffset, size: usize, options: GuestMemoryOptions) -> Result<Self> {
         Self::build(
             Some(file_offset),
             size,
             libc::PROT_READ | libc::PROT_WRITE,
             libc::MAP_NORESERVE | libc::MAP_SHARED,
+            options
         )
     }
 
@@ -132,6 +135,7 @@ impl MmapRegion {
         size: usize,
         prot: i32,
         flags: i32,
+        options: GuestMemoryOptions,
     ) -> Result<Self> {
         // Forbid MAP_FIXED, as it doesn't make sense in this context, and is pretty dangerous
         // in general.
@@ -154,6 +158,14 @@ impl MmapRegion {
             return Err(Error::Mmap(io::Error::last_os_error()));
         }
 
+        if options.huge_page {
+            if options.transparent_huge_page {
+                if size > 2 * 1024 * 4096 {
+                    let _ret = unsafe { libc::madvise(addr, size, libc::MADV_HUGEPAGE) };
+                }
+            }
+        }
+
         Ok(Self {
             addr: addr as *mut u8,
             size,