Annotate mmap ranges using PR_SET_VMA (#1236)

We demand that every invocation of `mmap` within mmtk-core to be
accompanied with an "annotation" for the purpose of the mmap. On Linux,
we will use `PR_SET_VMA_ANON_NAME` to set the attribute after `mmap` so
that it can be seen in `/proc/pid/maps`. This will greatly improve the
debugging experience.

Author: wks

Cargo.toml

@@ -179,6 +179,13 @@ count_live_bytes_in_gc = []
 # capture the type names of work packets.
 bpftrace_workaround = []
 
+# Disable mmap annotations.
+# All invocations of `mmap` in mmtk-core are accompanied by calls of `prctl` with
+# `PR_SET_VMA_ANON_NAME` to annotate the mmap ranges with human-readable names.  It is enabled by
+# default and should work fine even with large heap sizes.  However, if this is causing problems,
+# users can disable such annotations by enabling this Cargo feature.
+no_mmap_annotation = []
+
 # Do not modify the following line - ci-common.sh matches it
 # -- Mutally exclusive features --
 # Only one feature from each group can be provided. Otherwise build will fail.

docs/userguide/src/migration/prefix.md

@@ -30,6 +30,22 @@ Notes for the mmtk-core developers:
 
 <!-- Insert new versions here -->
 
+## 0.30.0
+
+### mmap-related functions require annotation
+
+```admonish tldr
+Memory-mapping functions in `mmtk::util::memory` now take an additional `MmapAnnotation` argument.
+```
+
+API changes:
+
+-   module `util::memory`
+    +   The following functions take an additional `MmapAnnotation` argument.
+        *   `dzmmap`
+        *   `dzmmap_noreplace`
+        *   `mmap_noreserve`
+
 ## 0.28.0
 
 ### `handle_user_collection_request` returns `bool`

src/policy/lockfreeimmortalspace.rs

@@ -13,6 +13,7 @@ use crate::util::heap::gc_trigger::GCTrigger;
 use crate::util::heap::layout::vm_layout::vm_layout;
 use crate::util::heap::PageResource;
 use crate::util::heap::VMRequest;
+use crate::util::memory::MmapAnnotation;
 use crate::util::memory::MmapStrategy;
 use crate::util::metadata::side_metadata::SideMetadataContext;
 use crate::util::metadata::side_metadata::SideMetadataSanity;
@@ -241,15 +242,22 @@ impl<VM: VMBinding> LockFreeImmortalSpace<VM> {
             *args.options.transparent_hugepages,
             crate::util::memory::MmapProtection::ReadWrite,
         );
-        crate::util::memory::dzmmap_noreplace(start, aligned_total_bytes, strategy).unwrap();
-        if space
+        crate::util::memory::dzmmap_noreplace(
+            start,
+            aligned_total_bytes,
+            strategy,
+            &MmapAnnotation::Space {
+                name: space.get_name(),
+            },
+        )
+        .unwrap();
+        space
             .metadata
-            .try_map_metadata_space(start, aligned_total_bytes)
-            .is_err()
-        {
-            // TODO(Javad): handle meta space allocation failure
-            panic!("failed to mmap meta memory");
-        }
+            .try_map_metadata_space(start, aligned_total_bytes, space.get_name())
+            .unwrap_or_else(|e| {
+                // TODO(Javad): handle meta space allocation failure
+                panic!("failed to mmap meta memory: {e}")
+            });
 
         space
     }

src/policy/marksweepspace/malloc_ms/global.rs

@@ -439,7 +439,7 @@ impl<VM: VMBinding> MallocSpace<VM> {
 
     fn map_metadata_and_update_bound(&self, addr: Address, size: usize) {
         // Map the metadata space for the range [addr, addr + size)
-        map_meta_space(&self.metadata, addr, size);
+        map_meta_space(&self.metadata, addr, size, self.get_name());
 
         // Update the bounds of the max and min chunk addresses seen -- this is used later in the sweep
         // Lockless compare-and-swap loops perform better than a locking variant

src/policy/marksweepspace/malloc_ms/metadata.rs

@@ -76,7 +76,7 @@ fn is_meta_space_mapped_for_address(address: Address) -> bool {
 }
 
 /// Eagerly map the active chunk metadata surrounding `chunk_start`
-fn map_active_chunk_metadata(chunk_start: Address) {
+fn map_active_chunk_metadata(chunk_start: Address, space_name: &str) {
     debug_assert!(chunk_start.is_aligned_to(BYTES_IN_CHUNK));
     // We eagerly map 16Gb worth of space for the chunk mark bytes on 64-bits
     // We require saturating subtractions in order to not overflow the chunk_start by
@@ -99,16 +99,20 @@ fn map_active_chunk_metadata(chunk_start: Address) {
         chunk_start + (size / 2)
     );
 
-    assert!(
-        CHUNK_METADATA.try_map_metadata_space(start, size).is_ok(),
-        "failed to mmap meta memory"
-    );
+    CHUNK_METADATA
+        .try_map_metadata_space(start, size, space_name)
+        .unwrap_or_else(|e| panic!("failed to mmap meta memory: {e}"));
 }
 
 /// We map the active chunk metadata (if not previously mapped), as well as the VO bit metadata
 /// and active page metadata here. Note that if [addr, addr + size) crosses multiple chunks, we
 /// will map for each chunk.
-pub(super) fn map_meta_space(metadata: &SideMetadataContext, addr: Address, size: usize) {
+pub(super) fn map_meta_space(
+    metadata: &SideMetadataContext,
+    addr: Address,
+    size: usize,
+    space_name: &str,
+) {
     // In order to prevent race conditions, we synchronize on the lock first and then
     // check if we need to map the active chunk metadata for `chunk_start`
     let _lock = CHUNK_MAP_LOCK.lock().unwrap();
@@ -118,7 +122,7 @@ pub(super) fn map_meta_space(metadata: &SideMetadataContext, addr: Address, size
         // Check if the chunk bit metadata is mapped. If it is not mapped, map it.
         // Note that the chunk bit metadata is global. It may have been mapped because other policy mapped it.
         if !is_chunk_mapped(start) {
-            map_active_chunk_metadata(start);
+            map_active_chunk_metadata(start, space_name);
         }
 
         // If we have set the chunk bit, return. This is needed just in case another thread has done this before
@@ -131,7 +135,8 @@ pub(super) fn map_meta_space(metadata: &SideMetadataContext, addr: Address, size
         // Note that this might fail. For example, we have marked a chunk as active but later we freed all
         // the objects in it, and unset its chunk bit. However, we do not free its metadata. So for the chunk,
         // its chunk bit is mapped, but not marked, and all its local metadata is also mapped.
-        let mmap_metadata_result = metadata.try_map_metadata_space(start, BYTES_IN_CHUNK);
+        let mmap_metadata_result =
+            metadata.try_map_metadata_space(start, BYTES_IN_CHUNK, space_name);
         debug_assert!(
             mmap_metadata_result.is_ok(),
             "mmap sidemetadata failed for chunk_start ({})",

src/policy/sft_map.rs

@@ -378,9 +378,11 @@ mod dense_chunk_map {
                 global: vec![SFT_DENSE_CHUNK_MAP_INDEX],
                 local: vec![],
             };
-            if context.try_map_metadata_space(start, bytes).is_err() {
-                panic!("failed to mmap metadata memory");
-            }
+            context
+                .try_map_metadata_space(start, bytes, "SFTDenseChunkMap")
+                .unwrap_or_else(|e| {
+                    panic!("failed to mmap metadata memory: {e}");
+                });
 
             self.update(space, start, bytes);
         }

src/policy/space.rs

@@ -144,12 +144,19 @@ pub trait Space<VM: VMBinding>: 'static + SFT + Sync + Downcast {
                         if let Err(mmap_error) = self
                             .common()
                             .mmapper
-                            .ensure_mapped(res.start, res.pages, self.common().mmap_strategy())
-                            .and(
-                                self.common()
-                                    .metadata
-                                    .try_map_metadata_space(res.start, bytes),
+                            .ensure_mapped(
+                                res.start,
+                                res.pages,
+                                self.common().mmap_strategy(),
+                                &memory::MmapAnnotation::Space {
+                                    name: self.get_name(),
+                                },
                             )
+                            .and(self.common().metadata.try_map_metadata_space(
+                                res.start,
+                                bytes,
+                                self.get_name(),
+                            ))
                         {
                             memory::handle_mmap_error::<VM>(mmap_error, tls, res.start, bytes);
                         }
@@ -293,15 +300,13 @@ pub trait Space<VM: VMBinding>: 'static + SFT + Sync + Downcast {
     /// Ensure this space is marked as mapped -- used when the space is already
     /// mapped (e.g. for a vm image which is externally mmapped.)
     fn ensure_mapped(&self) {
-        if self
-            .common()
+        self.common()
             .metadata
-            .try_map_metadata_space(self.common().start, self.common().extent)
-            .is_err()
-        {
-            // TODO(Javad): handle meta space allocation failure
-            panic!("failed to mmap meta memory");
-        }
+            .try_map_metadata_space(self.common().start, self.common().extent, self.get_name())
+            .unwrap_or_else(|e| {
+                // TODO(Javad): handle meta space allocation failure
+                panic!("failed to mmap meta memory: {e}");
+            });
 
         self.common()
             .mmapper
@@ -609,14 +614,12 @@ impl<VM: VMBinding> CommonSpace<VM> {
         }
 
         // For contiguous space, we know its address range so we reserve metadata memory for its range.
-        if rtn
-            .metadata
-            .try_map_metadata_address_range(rtn.start, rtn.extent)
-            .is_err()
-        {
-            // TODO(Javad): handle meta space allocation failure
-            panic!("failed to mmap meta memory");
-        }
+        rtn.metadata
+            .try_map_metadata_address_range(rtn.start, rtn.extent, rtn.name)
+            .unwrap_or_else(|e| {
+                // TODO(Javad): handle meta space allocation failure
+                panic!("failed to mmap meta memory: {e}");
+            });
 
         debug!(
             "Created space {} [{}, {}) for {} bytes",

src/policy/vmspace.rs

@@ -229,7 +229,7 @@ impl<VM: VMBinding> VMSpace<VM> {
         // Map side metadata
         self.common
             .metadata
-            .try_map_metadata_space(chunk_start, chunk_size)
+            .try_map_metadata_space(chunk_start, chunk_size, self.get_name())
             .unwrap();
         // Insert to vm map: it would be good if we can make VM map aware of the region. However, the region may be outside what we can map in our VM map implementation.
         // self.common.vm_map.insert(chunk_start, chunk_size, self.common.descriptor);

src/util/heap/layout/byte_map_mmapper.rs

@@ -1,5 +1,6 @@
 use super::mmapper::MapState;
 use super::Mmapper;
+use crate::util::memory::MmapAnnotation;
 use crate::util::Address;
 
 use crate::util::constants::*;
@@ -44,7 +45,13 @@ impl Mmapper for ByteMapMmapper {
         }
     }
 
-    fn ensure_mapped(&self, start: Address, pages: usize, strategy: MmapStrategy) -> Result<()> {
+    fn ensure_mapped(
+        &self,
+        start: Address,
+        pages: usize,
+        strategy: MmapStrategy,
+        anno: &MmapAnnotation,
+    ) -> Result<()> {
         let start_chunk = Self::address_to_mmap_chunks_down(start);
         let end_chunk = Self::address_to_mmap_chunks_up(start + pages_to_bytes(pages));
         trace!(
@@ -62,7 +69,8 @@ impl Mmapper for ByteMapMmapper {
 
             let mmap_start = Self::mmap_chunks_to_address(chunk);
             let _guard = self.lock.lock().unwrap();
-            MapState::transition_to_mapped(&self.mapped[chunk], mmap_start, strategy).unwrap();
+            MapState::transition_to_mapped(&self.mapped[chunk], mmap_start, strategy, anno)
+                .unwrap();
         }
 
         Ok(())
@@ -73,6 +81,7 @@ impl Mmapper for ByteMapMmapper {
         start: Address,
         pages: usize,
         strategy: MmapStrategy,
+        anno: &MmapAnnotation,
     ) -> Result<()> {
         let start_chunk = Self::address_to_mmap_chunks_down(start);
         let end_chunk = Self::address_to_mmap_chunks_up(start + pages_to_bytes(pages));
@@ -91,7 +100,8 @@ impl Mmapper for ByteMapMmapper {
 
             let mmap_start = Self::mmap_chunks_to_address(chunk);
             let _guard = self.lock.lock().unwrap();
-            MapState::transition_to_quarantined(&self.mapped[chunk], mmap_start, strategy).unwrap();
+            MapState::transition_to_quarantined(&self.mapped[chunk], mmap_start, strategy, anno)
+                .unwrap();
         }
 
         Ok(())
@@ -172,6 +182,7 @@ impl Default for ByteMapMmapper {
 #[cfg(test)]
 mod tests {
     use super::ByteMapMmapper;
+    use crate::mmap_anno_test;
     use crate::util::heap::layout::Mmapper;
     use crate::util::Address;
 
@@ -237,7 +248,7 @@ mod tests {
                 || {
                     let mmapper = ByteMapMmapper::new();
                     mmapper
-                        .ensure_mapped(FIXED_ADDRESS, pages, MmapStrategy::TEST)
+                        .ensure_mapped(FIXED_ADDRESS, pages, MmapStrategy::TEST, mmap_anno_test!())
                         .unwrap();
 
                     for chunk in start_chunk..end_chunk {
@@ -266,7 +277,7 @@ mod tests {
                 || {
                     let mmapper = ByteMapMmapper::new();
                     mmapper
-                        .ensure_mapped(FIXED_ADDRESS, pages, MmapStrategy::TEST)
+                        .ensure_mapped(FIXED_ADDRESS, pages, MmapStrategy::TEST, mmap_anno_test!())
                         .unwrap();
 
                     for chunk in start_chunk..end_chunk {
@@ -295,7 +306,7 @@ mod tests {
                 || {
                     let mmapper = ByteMapMmapper::new();
                     mmapper
-                        .ensure_mapped(FIXED_ADDRESS, pages, MmapStrategy::TEST)
+                        .ensure_mapped(FIXED_ADDRESS, pages, MmapStrategy::TEST, mmap_anno_test!())
                         .unwrap();
 
                     let start_chunk = ByteMapMmapper::address_to_mmap_chunks_down(FIXED_ADDRESS);
@@ -329,7 +340,12 @@ mod tests {
                     // map 2 chunks
                     let mmapper = ByteMapMmapper::new();
                     mmapper
-                        .ensure_mapped(FIXED_ADDRESS, test_memory_pages, MmapStrategy::TEST)
+                        .ensure_mapped(
+                            FIXED_ADDRESS,
+                            test_memory_pages,
+                            MmapStrategy::TEST,
+                            mmap_anno_test!(),
+                        )
                         .unwrap();
 
                     // protect 1 chunk
@@ -364,7 +380,12 @@ mod tests {
                     // map 2 chunks
                     let mmapper = ByteMapMmapper::new();
                     mmapper
-                        .ensure_mapped(FIXED_ADDRESS, test_memory_pages, MmapStrategy::TEST)
+                        .ensure_mapped(
+                            FIXED_ADDRESS,
+                            test_memory_pages,
+                            MmapStrategy::TEST,
+                            mmap_anno_test!(),
+                        )
                         .unwrap();
 
                     // protect 1 chunk
@@ -382,7 +403,12 @@ mod tests {
 
                     // ensure mapped - this will unprotect the previously protected chunk
                     mmapper
-                        .ensure_mapped(FIXED_ADDRESS, protect_memory_pages_2, MmapStrategy::TEST)
+                        .ensure_mapped(
+                            FIXED_ADDRESS,
+                            protect_memory_pages_2,
+                            MmapStrategy::TEST,
+                            mmap_anno_test!(),
+                        )
                         .unwrap();
                     assert_eq!(
                         mmapper.mapped[chunk].load(Ordering::Relaxed),