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Add memory page size alignment for madvise, mlock and munlock #19

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Add memory page size alignment for madvise, mlock and munlock #19

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b74967a
Add memory page size alignment for madvise, mlock and munlock
Eyob94 Sep 8, 2024
80b9cfa
Use Cached Page_size and test alignment function
Eyob94 Sep 11, 2024
422d653
test(addrs): :white_check_mark: add more tests for alignment function
Eyob94 Sep 11, 2024
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61 changes: 55 additions & 6 deletions src/mlock.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -2,20 +2,50 @@

#![cfg(feature = "use_os")]

use libc::_SC_PAGESIZE;

/// Retrieve page size of the system
///
/// Used for alignment
unsafe fn page_size() -> usize {
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We can use the page size cache in alloc mod.

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You're right, shouldn't be doing syscalls everytime we mlock/munlock. I've initialized the alloc_init() function and returned the PAGE_SIZE from the alloc module instead

use libc::sysconf;
sysconf(_SC_PAGESIZE) as usize
}

/// Cross-platform `mlock`.
///
/// * Unix `mlock`.
/// * Windows `VirtualLock`.
pub unsafe fn mlock(addr: *mut u8, len: usize) -> bool {
#[cfg(unix)]
{
let page_size = page_size();

// start address of the page obtained from masked the value of the page size
// with the memory address
//
let start_addr = (addr as usize) & !(page_size - 1);
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it should be put into a separate function and some tests added.

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I've refactored it out to a separate function, and added a few tests to check whether it returns the right start and end page offsets


// End address of the page
let end_addr = ((addr as usize) + len + page_size - 1) & !(page_size - 1);

let aligned_len = end_addr - start_addr;

#[cfg(target_os = "linux")]
libc::madvise(addr as *mut libc::c_void, len, libc::MADV_DONTDUMP);
libc::madvise(
start_addr as *mut libc::c_void,
aligned_len,
libc::MADV_DONTDUMP,
);

#[cfg(any(target_os = "freebsd", target_os = "dragonfly"))]
libc::madvise(addr as *mut libc::c_void, len, libc::MADV_NOCORE);
libc::madvise(
start_addr as *mut libc::c_void,
aligned_len,
libc::MADV_NOCORE,
);

libc::mlock(addr as *mut libc::c_void, len) == 0
libc::mlock(start_addr as *mut libc::c_void, aligned_len) == 0
}

#[cfg(windows)]
Expand All @@ -33,13 +63,32 @@ pub unsafe fn munlock(addr: *mut u8, len: usize) -> bool {

#[cfg(unix)]
{
let page_size = page_size();

// start address of the page obtained from masked the value of the page size
// with the memory address
//
let start_addr = (addr as usize) & !(page_size - 1);

// End address of the page
let end_addr = ((addr as usize) + len + page_size - 1) & !(page_size - 1);

let aligned_len = end_addr - start_addr;
#[cfg(target_os = "linux")]
libc::madvise(addr as *mut libc::c_void, len, libc::MADV_DODUMP);
libc::madvise(
start_addr as *mut libc::c_void,
aligned_len,
libc::MADV_DODUMP,
);

#[cfg(any(target_os = "freebsd", target_os = "dragonfly"))]
libc::madvise(addr as *mut libc::c_void, len, libc::MADV_CORE);
libc::madvise(
start_addr as *mut libc::c_void,
aligned_len,
libc::MADV_CORE,
);

libc::munlock(addr as *mut libc::c_void, len) == 0
libc::munlock(start_addr as *mut libc::c_void, aligned_len) == 0
}

#[cfg(windows)]
Expand Down