Add per-CPU counters and track RSS for each Vmar

kernel/src/fs/procfs/pid/status.rs

@@ -9,6 +9,7 @@ use crate::{
     },
     prelude::*,
     process::posix_thread::AsPosixThread,
+    vm::vmar::RssType,
     Process,
 };
 
@@ -97,6 +98,20 @@ impl FileOps for StatusFileOps {
             process.tasks().lock().as_slice().len()
         )
         .unwrap();
+
+        {
+            let vmar = process.lock_root_vmar();
+            let anon = vmar.unwrap().get_rss_counter(RssType::RSS_ANONPAGES) * (PAGE_SIZE / 1024);
+            let file = vmar.unwrap().get_rss_counter(RssType::RSS_FILEPAGES) * (PAGE_SIZE / 1024);
+            let rss = anon + file;
+            writeln!(
+                status_output,
+                "VmRSS:\t{} kB\nRssAnon:\t{} kB\nRssFile:\t{} kB",
+                rss, anon, file
+            )
+            .unwrap();
+        }
+
         Ok(status_output.into_bytes())
     }
 }

kernel/src/util/mod.rs

@@ -2,6 +2,7 @@
 
 mod iovec;
 pub mod net;
+pub mod per_cpu_counter;
 pub mod random;
 pub mod ring_buffer;
 

kernel/src/util/per_cpu_counter.rs

@@ -0,0 +1,54 @@
+// SPDX-License-Identifier: MPL-2.0
+
+//! A fast and scalable per-CPU counter.
+
+use core::sync::atomic::{AtomicIsize, Ordering};
+
+use osdk_heap_allocator::{alloc_cpu_local, CpuLocalBox};
+use ostd::cpu::{all_cpus, CpuId};
+
+/// A fast, SMP-friendly, dynamically allocated, per-CPU counter.
+///
+/// Updating it is fast and scalable, but reading is slow and inaccurate.
+///
+// TODO: Reuse the code from [`osdk_frame_allocator::fast_smp_counter`],
+// which may need to extract that code into a separate crate that needs
+// to be published. Do that after we somehow stabilize the per-CPU counter.
+pub struct PerCpuCounter {
+    per_cpu_counter: CpuLocalBox<AtomicIsize>,
+}
+
+impl PerCpuCounter {
+    /// Creates a new, zero-valued per-CPU counter.
+    pub fn new() -> Self {
+        Self {
+            per_cpu_counter: alloc_cpu_local(|_| AtomicIsize::new(0)).unwrap(),
+        }
+    }
+
+    /// Adds `increment` to the counter on the given CPU.
+    pub fn add(&self, on_cpu: CpuId, increment: isize) {
+        self.per_cpu_counter
+            .get_on_cpu(on_cpu)
+            .fetch_add(increment, Ordering::Relaxed);
+    }
+
+    /// Gets the total counter value.
+    ///
+    /// This function may be inaccurate since other CPUs may be
+    /// updating the counter.
+    pub fn get(&self) -> usize {
+        let mut total: isize = 0;
+        for cpu in all_cpus() {
+            total =
+                total.wrapping_add(self.per_cpu_counter.get_on_cpu(cpu).load(Ordering::Relaxed));
+        }
+        if total < 0 {
+            // The counter is unsigned. But an observer may see a negative
+            // value due to race conditions. We return zero if it happens.
+            0
+        } else {
+            total as usize
+        }
+    }
+}

kernel/src/vm/vmar/mod.rs

@@ -7,11 +7,12 @@ mod interval_set;
 mod static_cap;
 pub mod vm_mapping;
 
-use core::{num::NonZeroUsize, ops::Range};
+use core::{array, num::NonZeroUsize, ops::Range};
 
 use align_ext::AlignExt;
 use aster_rights::Rights;
 use ostd::{
+    cpu::CpuId,
     mm::{tlb::TlbFlushOp, PageFlags, PageProperty, VmSpace, MAX_USERSPACE_VADDR},
     task::disable_preempt,
 };
@@ -24,6 +25,7 @@ use crate::{
     prelude::*,
     process::{Process, ResourceType},
     thread::exception::PageFaultInfo,
+    util::per_cpu_counter::PerCpuCounter,
     vm::{
         perms::VmPerms,
         vmo::{Vmo, VmoRightsOp},
@@ -102,6 +104,8 @@ pub(super) struct Vmar_ {
     size: usize,
     /// The attached `VmSpace`
     vm_space: Arc<VmSpace>,
+    /// The RSS counters.
+    rss_counters: [PerCpuCounter; NUM_RSS_COUNTERS],
 }
 
 struct VmarInner {
@@ -195,6 +199,7 @@ impl VmarInner {
         vm_space: &VmSpace,
         offset: Vaddr,
         size: usize,
+        rss_delta: &mut RssDelta,
     ) -> Result<Range<Vaddr>> {
         let range = offset..offset + size;
         let mut mappings_to_remove = Vec::new();
@@ -215,7 +220,7 @@ impl VmarInner {
                 self.insert(right);
             }
 
-            taken.unmap(vm_space)?;
+            rss_delta.add(taken.rss_type(), -(taken.unmap(vm_space)? as isize));
         }
 
         Ok(offset..(offset + size))
@@ -280,19 +285,32 @@ impl Interval<usize> for Arc<Vmar_> {
 }
 
 impl Vmar_ {
-    fn new(inner: VmarInner, vm_space: Arc<VmSpace>, base: usize, size: usize) -> Arc<Self> {
+    fn new(
+        inner: VmarInner,
+        vm_space: Arc<VmSpace>,
+        base: usize,
+        size: usize,
+        rss_counters: [PerCpuCounter; NUM_RSS_COUNTERS],
+    ) -> Arc<Self> {
         Arc::new(Vmar_ {
             inner: RwMutex::new(inner),
             base,
             size,
             vm_space,
+            rss_counters,
         })
     }
 
     fn new_root() -> Arc<Self> {
         let vmar_inner = VmarInner::new();
         let vm_space = VmSpace::new();
-        Vmar_::new(vmar_inner, Arc::new(vm_space), 0, ROOT_VMAR_CAP_ADDR)
+        Vmar_::new(
+            vmar_inner,
+            Arc::new(vm_space),
+            0,
+            ROOT_VMAR_CAP_ADDR,
+            array::from_fn(|_| PerCpuCounter::new()),
+        )
     }
 
     fn protect(&self, perms: VmPerms, range: Range<usize>) -> Result<()> {
@@ -350,7 +368,10 @@ impl Vmar_ {
 
         if let Some(vm_mapping) = inner.vm_mappings.find_one(&address) {
             debug_assert!(vm_mapping.range().contains(&address));
-            return vm_mapping.handle_page_fault(&self.vm_space, page_fault_info);
+
+            let rss_increment = vm_mapping.handle_page_fault(&self.vm_space, page_fault_info)?;
+            self.add_rss_counter(vm_mapping.rss_type(), rss_increment as isize);
+            return Ok(());
         }
 
         return_errno_with_message!(Errno::EACCES, "page fault addr is not in current vmar");
@@ -376,7 +397,14 @@ impl Vmar_ {
 
     pub fn remove_mapping(&self, range: Range<usize>) -> Result<()> {
         let mut inner = self.inner.write();
-        inner.alloc_free_region_exact_truncate(&self.vm_space, range.start, range.len())?;
+        let mut rss_delta = RssDelta::new();
+        inner.alloc_free_region_exact_truncate(
+            &self.vm_space,
+            range.start,
+            range.len(),
+            &mut rss_delta,
+        )?;
+        self.add_rss_delta(rss_delta);
         Ok(())
     }
 
@@ -426,7 +454,13 @@ impl Vmar_ {
         let new_vmar_ = {
             let vmar_inner = VmarInner::new();
             let new_space = VmSpace::new();
-            Vmar_::new(vmar_inner, Arc::new(new_space), self.base, self.size)
+            Vmar_::new(
+                vmar_inner,
+                Arc::new(new_space),
+                self.base,
+                self.size,
+                array::from_fn(|_| PerCpuCounter::new()),
+            )
         };
 
         {
@@ -440,6 +474,8 @@ impl Vmar_ {
             let mut new_cursor = new_vmspace.cursor_mut(&preempt_guard, &range).unwrap();
             let cur_vmspace = self.vm_space();
             let mut cur_cursor = cur_vmspace.cursor_mut(&preempt_guard, &range).unwrap();
+            let mut rss_delta = RssDelta::new();
+
             for vm_mapping in inner.vm_mappings.iter() {
                 let base = vm_mapping.map_to_addr();
 
@@ -453,8 +489,12 @@ impl Vmar_ {
                 let mut op = |page: &mut PageProperty| {
                     page.flags -= PageFlags::W;
                 };
-                new_cursor.copy_from(&mut cur_cursor, vm_mapping.map_size(), &mut op);
+                let num_mapped =
+                    new_cursor.copy_from(&mut cur_cursor, vm_mapping.map_size(), &mut op);
+                rss_delta.add(vm_mapping.rss_type(), num_mapped as isize);
             }
+            new_vmar_.add_rss_delta(rss_delta);
+
             cur_cursor.flusher().issue_tlb_flush(TlbFlushOp::All);
             cur_cursor.flusher().dispatch_tlb_flush();
             cur_cursor.flusher().sync_tlb_flush();
@@ -462,6 +502,24 @@ impl Vmar_ {
 
         Ok(new_vmar_)
     }
+
+    pub fn get_rss_counter(&self, rss_type: RssType) -> usize {
+        self.rss_counters[rss_type as usize].get()
+    }
+
+    fn add_rss_counter(&self, rss_type: RssType, val: isize) {
+        // There are races but updating a remote counter won't cause any problems.
+        let cpu_id = CpuId::current_racy();
+        self.rss_counters[rss_type as usize].add(cpu_id, val);
+    }
+
+    fn add_rss_delta(&self, rss_delta: RssDelta) {
+        for i in 0..NUM_RSS_COUNTERS {
+            let rss_type = RssType::try_from(i).unwrap();
+            let delta = rss_delta.get(rss_type);
+            self.add_rss_counter(rss_type, delta);
+        }
+    }
 }
 
 impl<R> Vmar<R> {
@@ -476,6 +534,11 @@ impl<R> Vmar<R> {
     pub fn size(&self) -> usize {
         self.0.size
     }
+
+    /// Returns the current RSS count for the given RSS type.
+    pub fn get_rss_counter(&self, rss_type: RssType) -> usize {
+        self.0.get_rss_counter(rss_type)
+    }
 }
 
 /// Options for creating a new mapping. The mapping is not allowed to overlap
@@ -659,7 +722,14 @@ where
                 Errno::EINVAL,
                 "offset cannot be None since can overwrite is set",
             ))?;
-            inner.alloc_free_region_exact_truncate(parent.vm_space(), offset, map_size)?;
+            let mut rss_delta = RssDelta::new();
+            inner.alloc_free_region_exact_truncate(
+                parent.vm_space(),
+                offset,
+                map_size,
+                &mut rss_delta,
+            )?;
+            parent.0.add_rss_delta(rss_delta);
             offset
         } else if let Some(offset) = offset {
             inner.alloc_free_region_exact(offset, map_size)?;
@@ -735,3 +805,32 @@ pub fn get_intersected_range(range1: &Range<usize>, range2: &Range<usize>) -> Ra
     debug_assert!(is_intersected(range1, range2));
     range1.start.max(range2.start)..range1.end.min(range2.end)
 }
+
+/// The type representing categories of Resident Set Size (RSS).
+///
+/// See <https://github.com/torvalds/linux/blob/fac04efc5c793dccbd07e2d59af9f90b7fc0dca4/include/linux/mm_types_task.h#L26..L32>
+#[repr(usize)]
+#[expect(non_camel_case_types)]
+#[derive(Debug, Clone, Copy, TryFromInt)]
+pub enum RssType {
+    RSS_FILEPAGES = 0,
+    RSS_ANONPAGES = 1,
+}
+
+const NUM_RSS_COUNTERS: usize = 2;
+
+struct RssDelta([isize; NUM_RSS_COUNTERS]);
+
+impl RssDelta {
+    pub(self) fn new() -> Self {
+        Self([0; NUM_RSS_COUNTERS])
+    }
+
+    pub(self) fn add(&mut self, rss_type: RssType, increment: isize) {
+        self.0[rss_type as usize] += increment;
+    }
+
+    pub(self) fn get(&self, rss_type: RssType) -> isize {
+        self.0[rss_type as usize]
+    }
+}

kernel/src/vm/vmar/vm_mapping.rs

@@ -15,7 +15,7 @@ use ostd::{
     task::disable_preempt,
 };
 
-use super::interval_set::Interval;
+use super::{interval_set::Interval, RssType};
 use crate::{
     prelude::*,
     thread::exception::PageFaultInfo,
@@ -124,16 +124,26 @@ impl VmMapping {
     pub fn perms(&self) -> VmPerms {
         self.perms
     }
+
+    // Returns the mapping's RSS type.
+    pub fn rss_type(&self) -> RssType {
+        if self.vmo.is_none() {
+            RssType::RSS_ANONPAGES
+        } else {
+            RssType::RSS_FILEPAGES
+        }
+    }
 }
 
 /****************************** Page faults **********************************/
 
 impl VmMapping {
+    /// Handles a page fault and returns the number of pages mapped.
     pub fn handle_page_fault(
         &self,
         vm_space: &VmSpace,
         page_fault_info: &PageFaultInfo,
-    ) -> Result<()> {
+    ) -> Result<usize> {
         if !self.perms.contains(page_fault_info.required_perms) {
             trace!(
                 "self.perms {:?}, page_fault_info.required_perms {:?}, self.range {:?}",
@@ -150,7 +160,7 @@ impl VmMapping {
         let is_write = page_fault_info.required_perms.contains(VmPerms::WRITE);
 
         if !is_write && self.vmo.is_some() && self.handle_page_faults_around {
-            let res = self.handle_page_faults_around(vm_space, address);
+            let (rss_increment, res) = self.handle_page_faults_around(vm_space, address);
 
             // Errors caused by the "around" pages should be ignored, so here we
             // only return the error if the faulting page is still not mapped.
@@ -161,13 +171,14 @@ impl VmMapping {
                     &(page_aligned_addr..page_aligned_addr + PAGE_SIZE),
                 )?;
                 if let VmItem::Mapped { .. } = cursor.query().unwrap() {
-                    return Ok(());
+                    return Ok(rss_increment);
                 }
             }
 
-            return res;
+            return res.map(|_| rss_increment);
         }
 
+        let mut rss_increment: usize = 0;
         'retry: loop {
             let preempt_guard = disable_preempt();
             let mut cursor = vm_space.cursor_mut(
@@ -185,14 +196,14 @@ impl VmMapping {
                         // The page fault is already handled maybe by other threads.
                         // Just flush the TLB and return.
                         TlbFlushOp::Address(va).perform_on_current();
-                        return Ok(());
+                        return Ok(0);
                     }
                     assert!(is_write);
                     // Perform COW if it is a write access to a shared mapping.
 
                     // Skip if the page fault is already handled.
                     if prop.flags.contains(PageFlags::W) {
-                        return Ok(());
+                        return Ok(0);
                     }
 
                     // If the forked child or parent immediately unmaps the page after
@@ -212,6 +223,7 @@ impl VmMapping {
                         let new_frame = duplicate_frame(&frame)?;
                         prop.flags |= new_flags;
                         cursor.map(new_frame.into(), prop);
+                        rss_increment += 1;
                     }
                     cursor.flusher().sync_tlb_flush();
                 }
@@ -248,11 +260,13 @@ impl VmMapping {
                     let map_prop = PageProperty::new_user(page_flags, CachePolicy::Writeback);
 
                     cursor.map(frame, map_prop);
+                    rss_increment += 1;
                 }
             }
             break 'retry;
         }
-        Ok(())
+
+        Ok(rss_increment)
     }
 
     fn prepare_page(
@@ -285,7 +299,15 @@ impl VmMapping {
         }
     }
 
-    fn handle_page_faults_around(&self, vm_space: &VmSpace, page_fault_addr: Vaddr) -> Result<()> {
+    /// Handles a page fault and maps additional surrounding pages.
+    ///
+    /// Returns a tuple `(mapped_pages, result)`, where `mapped_pages` is the number
+    /// of pages mapped successfully, even if the `result` is some error.
+    fn handle_page_faults_around(
+        &self,
+        vm_space: &VmSpace,
+        page_fault_addr: Vaddr,
+    ) -> (usize, Result<()>) {
         const SURROUNDING_PAGE_NUM: usize = 16;
         const SURROUNDING_PAGE_ADDR_MASK: usize = !(SURROUNDING_PAGE_NUM * PAGE_SIZE - 1);
 
@@ -300,9 +322,19 @@ impl VmMapping {
         );
 
         let vm_perms = self.perms - VmPerms::WRITE;
+        let mut rss_increment: usize = 0;
+
         'retry: loop {
             let preempt_guard = disable_preempt();
-            let mut cursor = vm_space.cursor_mut(&preempt_guard, &(start_addr..end_addr))?;
+
+            let mut cursor = match vm_space.cursor_mut(&preempt_guard, &(start_addr..end_addr)) {
+                Ok(cursor) => cursor,
+                Err(e) => {
+                    return (rss_increment, Err(e.into()));
+                }
+            };
+
+            let rss_increment_ref = &mut rss_increment;
             let operate =
                 move |commit_fn: &mut dyn FnMut()
                     -> core::result::Result<UFrame, VmoCommitError>| {
@@ -314,6 +346,7 @@ impl VmMapping {
                         let page_prop = PageProperty::new_user(page_flags, CachePolicy::Writeback);
                         let frame = commit_fn()?;
                         cursor.map(frame, page_prop);
+                        *rss_increment_ref += 1;
                     } else {
                         let next_addr = cursor.virt_addr() + PAGE_SIZE;
                         if next_addr < end_addr {
@@ -326,14 +359,16 @@ impl VmMapping {
             let start_offset = start_addr - self.map_to_addr;
             let end_offset = end_addr - self.map_to_addr;
             match vmo.try_operate_on_range(&(start_offset..end_offset), operate) {
-                Ok(_) => return Ok(()),
+                Ok(_) => return (rss_increment, Ok(())),
                 Err(VmoCommitError::NeedIo(index)) => {
                     drop(preempt_guard);
-                    vmo.commit_on(index, CommitFlags::empty())?;
+                    if let Err(e) = vmo.commit_on(index, CommitFlags::empty()) {
+                        return (rss_increment, Err(e));
+                    }
                     start_addr = index * PAGE_SIZE + self.map_to_addr;
                     continue 'retry;
                 }
-                Err(VmoCommitError::Err(e)) => return Err(e),
+                Err(VmoCommitError::Err(e)) => return (rss_increment, Err(e)),
             }
         }
     }
@@ -429,17 +464,18 @@ impl VmMapping {
 /************************** VM Space operations ******************************/
 
 impl VmMapping {
-    /// Unmaps the mapping from the VM space.
+    /// Unmaps the mapping from the VM space,
-    pub(super) fn unmap(self, vm_space: &VmSpace) -> Result<()> {
+    /// and returns the number of unmapped pages.
+    pub(super) fn unmap(self, vm_space: &VmSpace) -> Result<usize> {
         let preempt_guard = disable_preempt();
         let range = self.range();
         let mut cursor = vm_space.cursor_mut(&preempt_guard, &range)?;
 
-        cursor.unmap(range.len());
+        let num_unmapped = cursor.unmap(range.len());
         cursor.flusher().dispatch_tlb_flush();
         cursor.flusher().sync_tlb_flush();
 
-        Ok(())
+        Ok(num_unmapped)
     }
 
     /// Change the perms of the mapping.

ostd/src/mm/page_table/cursor/locking.rs

@@ -246,7 +246,8 @@ unsafe fn dfs_release_lock<'rcu, E: PageTableEntryTrait, C: PagingConstsTrait>(
     }
 }
 
-/// Marks all the nodes in the sub-tree rooted at the node as stray.
+/// Marks all the nodes in the sub-tree rooted at the node as stray, and
+/// returns the num of pages mapped within the sub-tree.
 ///
 /// This function must be called upon the node after the node is removed
 /// from the parent page table.
@@ -263,13 +264,15 @@ unsafe fn dfs_release_lock<'rcu, E: PageTableEntryTrait, C: PagingConstsTrait>(
 pub(super) unsafe fn dfs_mark_stray_and_unlock<E: PageTableEntryTrait, C: PagingConstsTrait>(
     rcu_guard: &dyn InAtomicMode,
     mut sub_tree: PageTableGuard<E, C>,
-) {
+) -> usize {
     *sub_tree.stray_mut() = true;
 
     if sub_tree.level() == 1 {
-        return;
+        return sub_tree.nr_children() as usize;
     }
 
+    let mut num_pages = 0;
+
     for i in (0..nr_subpage_per_huge::<C>()).rev() {
         let child = sub_tree.entry(i);
         match child.to_ref() {
@@ -278,11 +281,13 @@ pub(super) unsafe fn dfs_mark_stray_and_unlock<E: PageTableEntryTrait, C: Paging
                 let locked_pt = unsafe { pt.make_guard_unchecked(rcu_guard) };
                 // SAFETY: The caller ensures that all the nodes in the sub-tree are locked and all
                 // guards are forgotten.
-                unsafe { dfs_mark_stray_and_unlock(rcu_guard, locked_pt) };
+                num_pages += unsafe { dfs_mark_stray_and_unlock(rcu_guard, locked_pt) };
             }
             Child::None | Child::Frame(_, _) | Child::Untracked(_, _, _) | Child::PageTable(_) => {}
         }
     }
+
+    num_pages
 }
 
 fn dfs_get_idx_range<C: PagingConstsTrait>(

ostd/src/mm/page_table/cursor/mod.rs

@@ -102,6 +102,7 @@ pub enum PageTableItem {
         pt: Frame<dyn AnyFrameMeta>,
         va: Vaddr,
         len: usize,
+        num_pages: usize,
     },
 }
 
@@ -600,12 +601,14 @@ impl<'rcu, M: PageTableMode, E: PageTableEntryTrait, C: PagingConstsTrait>
                     // SAFETY:
                     //  - We checked that we are not unmapping shared kernel page table nodes.
                     //  - We must have locked the entire sub-tree since the range is locked.
-                    unsafe { locking::dfs_mark_stray_and_unlock(rcu_guard, locked_pt) };
+                    let num_pages =
+                        unsafe { locking::dfs_mark_stray_and_unlock(rcu_guard, locked_pt) };
 
                     PageTableItem::StrayPageTable {
                         pt: (*pt).clone().into(),
                         va: self.0.va,
                         len: page_size::<C>(self.0.level),
+                        num_pages,
                     }
                 }
                 Child::None | Child::PageTableRef(_) => unreachable!(),
@@ -705,7 +708,8 @@ impl<'rcu, M: PageTableMode, E: PageTableEntryTrait, C: PagingConstsTrait>
         None
     }
 
-    /// Copies the mapping from the given cursor to the current cursor.
+    /// Copies the mapping from the given cursor to the current cursor,
+    /// and returns the num of pages mapped by the current cursor.
     ///
     /// All the mappings in the current cursor's range must be empty. The
     /// function allows the source cursor to operate on the mapping before
@@ -737,7 +741,7 @@ impl<'rcu, M: PageTableMode, E: PageTableEntryTrait, C: PagingConstsTrait>
         src: &mut Self,
         len: usize,
         op: &mut impl FnMut(&mut PageProperty),
-    ) {
+    ) -> usize {
         assert!(len % page_size::<C>(1) == 0);
         let this_end = self.0.va + len;
         assert!(this_end <= self.0.barrier_va.end);
@@ -746,6 +750,7 @@ impl<'rcu, M: PageTableMode, E: PageTableEntryTrait, C: PagingConstsTrait>
 
         let rcu_guard = self.0.rcu_guard;
 
+        let mut num_mapped: usize = 0;
         while self.0.va < this_end && src.0.va < src_end {
             let src_va = src.0.va;
             let mut src_entry = src.0.cur_entry();
@@ -789,9 +794,13 @@ impl<'rcu, M: PageTableMode, E: PageTableEntryTrait, C: PagingConstsTrait>
                     // This assertion is to ensure that they move by the same length.
                     debug_assert_eq!(mapped_page_size, page_size::<C>(src.0.level));
                     src.0.move_forward();
+
+                    num_mapped += 1;
                 }
             }
         }
+
+        num_mapped
     }
 }
 

ostd/src/mm/vm_space.rs

@@ -289,7 +289,8 @@ impl<'a> CursorMut<'a> {
         }
     }
 
-    /// Clear the mapping starting from the current slot.
+    /// Clears the mapping starting from the current slot,
+    /// and returns the number of unmapped pages.
     ///
     /// This method will bring the cursor forward by `len` bytes in the virtual
     /// address space after the modification.
@@ -305,15 +306,16 @@ impl<'a> CursorMut<'a> {
     /// # Panics
     ///
     /// This method will panic if `len` is not page-aligned.
-    pub fn unmap(&mut self, len: usize) {
+    pub fn unmap(&mut self, len: usize) -> usize {
         assert!(len % super::PAGE_SIZE == 0);
         let end_va = self.virt_addr() + len;
-
+        let mut num_unmapped: usize = 0;
         loop {
             // SAFETY: It is safe to un-map memory in the userspace.
             let result = unsafe { self.pt_cursor.take_next(end_va - self.virt_addr()) };
             match result {
                 PageTableItem::Mapped { va, page, .. } => {
+                    num_unmapped += 1;
                     self.flusher
                         .issue_tlb_flush_with(TlbFlushOp::Address(va), page);
                 }
@@ -323,7 +325,13 @@ impl<'a> CursorMut<'a> {
                 PageTableItem::MappedUntracked { .. } => {
                     panic!("found untracked memory mapped into `VmSpace`");
                 }
-                PageTableItem::StrayPageTable { pt, va, len } => {
+                PageTableItem::StrayPageTable {
+                    pt,
+                    va,
+                    len,
+                    num_pages,
+                } => {
+                    num_unmapped += num_pages;
                     self.flusher
                         .issue_tlb_flush_with(TlbFlushOp::Range(va..va + len), pt);
                 }
@@ -331,6 +339,7 @@ impl<'a> CursorMut<'a> {
         }
 
         self.flusher.dispatch_tlb_flush();
+        num_unmapped
     }
 
     /// Applies the operation to the next slot of mapping within the range.
@@ -365,7 +374,8 @@ impl<'a> CursorMut<'a> {
         unsafe { self.pt_cursor.protect_next(len, &mut op) }
     }
 
-    /// Copies the mapping from the given cursor to the current cursor.
+    /// Copies the mapping from the given cursor to the current cursor,
+    /// and returns the num of pages mapped by the current cursor.
     ///
     /// All the mappings in the current cursor's range must be empty. The
     /// function allows the source cursor to operate on the mapping before
@@ -391,7 +401,7 @@ impl<'a> CursorMut<'a> {
         src: &mut Self,
         len: usize,
         op: &mut impl FnMut(&mut PageProperty),
-    ) {
+    ) -> usize {
         // SAFETY: Operations on user memory spaces are safe if it doesn't
         // involve dropping any pages.
         unsafe { self.pt_cursor.copy_from(&mut src.pt_cursor, len, op) }

test/apps/mmap/mmap_vmrss.c

@@ -0,0 +1,152 @@
+// SPDX-License-Identifier: MPL-2.0
+
+#define _GNU_SOURCE
+
+#include "../network/test.h"
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <sys/mman.h>
+#include <fcntl.h>
+
+#define PAGE_SIZE 4096
+#define NUM_PAGES 1024
+#define TOTAL_SIZE (PAGE_SIZE * NUM_PAGES)
+
+typedef enum rss_type {
+	anon,
+	file,
+	total,
+} rss_type;
+
+long get_vm_rss_kb(rss_type type)
+{
+	pid_t pid = getpid();
+	char path[64];
+	snprintf(path, sizeof(path), "/proc/%d/status", pid);
+
+	FILE *f = fopen(path, "r");
+	if (!f) {
+		perror("fopen /proc/[pid]/status");
+		exit(1);
+	}
+
+	char line[256];
+	long rss_kb = -1;
+	const char *target_field = NULL;
+	switch (type) {
+	case anon:
+		target_field = "RssAnon:";
+		break;
+	case file:
+		target_field = "RssFile:";
+		break;
+	case total:
+		target_field = "VmRSS:";
+		break;
+	default:
+		perror("Unknown rss_type\n");
+		exit(1);
+	}
+
+	while (fgets(line, sizeof(line), f)) {
+		if (strncmp(line, target_field, strlen(target_field)) == 0) {
+			sscanf(line + strlen(target_field), "%ld", &rss_kb);
+			break;
+		}
+	}
+
+	fclose(f);
+
+	if (rss_kb < 0) {
+		fprintf(stderr, "Failed to parse VmRSS\n");
+		exit(1);
+	}
+
+	return rss_kb;
+}
+
+FN_TEST(rss_anon)
+{
+	void *mem = mmap(NULL, TOTAL_SIZE, PROT_READ | PROT_WRITE,
+			 MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
+	if (mem == MAP_FAILED) {
+		perror("mmap");
+		exit(1);
+	}
+
+	// The first call to `TEST_SUCC` and `get_vm_rss_kb()` may trigger
+	// lazy mapping of additional pages, such as shared libraries or files.
+	// These pages are not counted in RSS until they are actually accessed.
+	TEST_SUCC(get_vm_rss_kb(anon));
+
+	long rss_anon_before = TEST_SUCC(get_vm_rss_kb(anon));
+	long rss_file_before = TEST_SUCC(get_vm_rss_kb(file));
+	long rss_before = TEST_SUCC(get_vm_rss_kb(total));
+
+	// Trigger page faults
+	for (int i = 0; i < NUM_PAGES; ++i) {
+		volatile char *p = (char *)mem + i * PAGE_SIZE;
+		*p = 42;
+	}
+
+	TEST_RES(get_vm_rss_kb(anon),
+		 _ret - rss_anon_before == NUM_PAGES * (PAGE_SIZE / 1024));
+	TEST_RES(get_vm_rss_kb(file), _ret == rss_file_before);
+	TEST_RES(get_vm_rss_kb(total),
+		 _ret - rss_before == NUM_PAGES * (PAGE_SIZE / 1024));
+
+	TEST_SUCC(munmap(mem, TOTAL_SIZE));
+
+	TEST_RES(get_vm_rss_kb(anon), _ret == rss_anon_before);
+	TEST_RES(get_vm_rss_kb(file), _ret == rss_file_before);
+	TEST_RES(get_vm_rss_kb(total), _ret == rss_before);
+}
+END_TEST()
+
+FN_TEST(rss_file)
+{
+	const char *filename = "rss_test_file";
+	int fd = TEST_SUCC(open(filename, O_CREAT | O_RDWR, 0600));
+
+	TEST_SUCC(ftruncate(fd, TOTAL_SIZE));
+
+	// The first call to `TEST_SUCC` and `get_vm_rss_kb()` may trigger
+	// lazy mapping of additional pages, such as shared libraries or files.
+	// These pages are not counted in RSS until they are actually accessed.
+	TEST_SUCC(get_vm_rss_kb(anon));
+
+	long rss_anon_before = TEST_SUCC(get_vm_rss_kb(anon));
+	long rss_file_before = TEST_SUCC(get_vm_rss_kb(file));
+	long rss_before = TEST_SUCC(get_vm_rss_kb(total));
+
+	void *mem = mmap(NULL, TOTAL_SIZE, PROT_READ, MAP_PRIVATE, fd, 0);
+	if (mem == MAP_FAILED) {
+		perror("mmap");
+		exit(1);
+	}
+
+	// Trigger page faults
+	for (int i = 0; i < NUM_PAGES; ++i) {
+		volatile char x = *((char *)mem + i * PAGE_SIZE);
+		x++;
+	}
+
+	TEST_RES(get_vm_rss_kb(file),
+		 _ret - rss_file_before == NUM_PAGES * (PAGE_SIZE / 1024));
+	TEST_RES(get_vm_rss_kb(anon), _ret == rss_anon_before);
+	TEST_RES(get_vm_rss_kb(total),
+		 _ret - rss_before == NUM_PAGES * (PAGE_SIZE / 1024));
+
+	TEST_SUCC(munmap(mem, TOTAL_SIZE));
+
+	TEST_RES(get_vm_rss_kb(anon), _ret == rss_anon_before);
+	TEST_RES(get_vm_rss_kb(file), _ret == rss_file_before);
+	TEST_RES(get_vm_rss_kb(total), _ret == rss_before);
+
+	close(fd);
+	unlink(filename);
+}
+END_TEST()

test/apps/scripts/process.sh

@@ -30,6 +30,7 @@ itimer/timer_create
 mmap/mmap_and_fork
 mmap/mmap_shared_filebacked
 mmap/mmap_readahead
+mmap/mmap_vmrss
 process/group_session
 process/job_control
 pthread/pthread_test