implement MappedPageBox by RajeshRk18 · Pull Request #2688 · hermit-os/kernel

RajeshRk18 · 2026-08-30T15:24:15Z

Added MappedPageBox and used it in two call sites.

Also removed #[expect(dead_code)] in src/arch/aarch64/mm/paging.rs because new public API makes it externally reachable.

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Benchmark Results

Details

Benchmark	Current: `60d883d`	Previous: `2e23902`	Performance Ratio
startup_benchmark Build Time	`90.69` s	`80.34` s	`1.13` ❗
startup_benchmark File Size	`0.81` MB	`0.80` MB	`1.01` ❗
Startup Time - 1 core	`0.71` s (`±0.02` s)	`0.75` s (`±0.02` s)	`0.96` ❗
Startup Time - 2 cores	`0.72` s (`±0.03` s)	`0.74` s (`±0.02` s)	`0.98`
Startup Time - 4 cores	`0.74` s (`±0.02` s)	`0.74` s (`±0.02` s)	`1.00`
multithreaded_benchmark Build Time	`91.57` s	`82.11` s	`1.12` ❗
multithreaded_benchmark File Size	`0.94` MB	`0.86` MB	`1.10` ❗
Multithreaded Pi Efficiency - 2 Threads	`88.53` % (`±8.22` %)	`85.89` % (`±6.61` %)	`1.03`
Multithreaded Pi Efficiency - 4 Threads	`43.98` % (`±2.89` %)	`43.43` % (`±2.56` %)	`1.01`
Multithreaded Pi Efficiency - 8 Threads	`25.69` % (`±1.79` %)	`25.76` % (`±1.53` %)	`1.00`
micro_benchmarks Build Time	`87.62` s	`80.40` s	`1.09` ❗
micro_benchmarks File Size	`0.94` MB	`0.86` MB	`1.09` ❗
Scheduling time - 1 thread	`64.85` ticks (`±2.43` ticks)	`62.65` ticks (`±4.06` ticks)	`1.03`
Scheduling time - 2 threads	`35.46` ticks (`±4.28` ticks)	`34.08` ticks (`±4.10` ticks)	`1.04`
Micro - Time for syscall (getpid)	`3.65` ticks (`±0.63` ticks)	`3.45` ticks (`±0.58` ticks)	`1.06`
Memcpy speed - (built_in) block size 4096	`81552.28` MByte/s (`±56589.09` MByte/s)	`82448.38` MByte/s (`±56997.13` MByte/s)	`0.99`
Memcpy speed - (built_in) block size 1048576	`30177.17` MByte/s (`±24389.45` MByte/s)	`30585.98` MByte/s (`±24707.84` MByte/s)	`0.99`
Memcpy speed - (built_in) block size 16777216	`26201.14` MByte/s (`±21675.53` MByte/s)	`26340.06` MByte/s (`±21720.96` MByte/s)	`0.99`
Memset speed - (built_in) block size 4096	`81128.27` MByte/s (`±56295.48` MByte/s)	`82292.76` MByte/s (`±56891.50` MByte/s)	`0.99`
Memset speed - (built_in) block size 1048576	`30954.88` MByte/s (`±24847.07` MByte/s)	`31323.85` MByte/s (`±25145.86` MByte/s)	`0.99`
Memset speed - (built_in) block size 16777216	`26996.62` MByte/s (`±22202.46` MByte/s)	`27104.68` MByte/s (`±22209.94` MByte/s)	`1.00`
Memcpy speed - (rust) block size 4096	`74466.68` MByte/s (`±52086.33` MByte/s)	`74097.96` MByte/s (`±51811.44` MByte/s)	`1.00`
Memcpy speed - (rust) block size 1048576	`30025.33` MByte/s (`±24350.52` MByte/s)	`30361.60` MByte/s (`±24602.37` MByte/s)	`0.99`
Memcpy speed - (rust) block size 16777216	`26740.98` MByte/s (`±22157.28` MByte/s)	`27625.34` MByte/s (`±22806.88` MByte/s)	`0.97`
Memset speed - (rust) block size 4096	`74956.38` MByte/s (`±52454.30` MByte/s)	`74373.47` MByte/s (`±51976.48` MByte/s)	`1.01`
Memset speed - (rust) block size 1048576	`30773.55` MByte/s (`±24807.76` MByte/s)	`31110.89` MByte/s (`±25033.24` MByte/s)	`0.99`
Memset speed - (rust) block size 16777216	`27542.57` MByte/s (`±22677.26` MByte/s)	`28386.93` MByte/s (`±23265.03` MByte/s)	`0.97`
alloc_benchmarks Build Time	`83.62` s	`74.76` s	`1.12` ❗
alloc_benchmarks File Size	`0.89` MB	`0.87` MB	`1.01` ❗
Allocations - Allocation success	`91.37` %	`91.31` %	`1.00` ❗
Allocations - Deallocation success	`100.00` %	`100.00` %	`1`
Allocations - Pre-fail Allocations	`61.61` %	`61.44` %	`1.00` ❗
Allocations - Average Allocation time	`2705.78` Ticks (`±756.99` Ticks)	`5860.58` Ticks (`±98.43` Ticks)	`0.46` ❗
Allocations - Average Allocation time (no fail)	`3726.23` Ticks (`±660.87` Ticks)	`6554.81` Ticks (`±92.86` Ticks)	`0.57` ❗
Allocations - Average Deallocation time	`737.77` Ticks (`±118.96` Ticks)	`1805.01` Ticks (`±250.35` Ticks)	`0.41` ❗
mutex_benchmark Build Time	`100.31` s	`79.82` s	`1.26` ❗
mutex_benchmark File Size	`0.94` MB	`0.86` MB	`1.09` ❗
Mutex Stress Test Average Time per Iteration - 1 Threads	`12.46` ns (`±0.57` ns)	`12.10` ns (`±0.41` ns)	`1.03`
Mutex Stress Test Average Time per Iteration - 2 Threads	`71.76` ns (`±3.85` ns)	`40.26` ns (`±1.68` ns)	`1.78` ❗

This comment was automatically generated by workflow using github-action-benchmark.

mkroening

Thanks! Did you use any AI assistance? :)

mkroening · 2026-08-30T16:58:05Z

+		// `paging::unmap` only flushes the TLB of this CPU. Request the flush on
+		// all other CPUs before the frames can be reused.
+		#[cfg(all(target_arch = "x86_64", feature = "smp"))]
+		crate::arch::kernel::apic::ipi_tlb_flush();


This seems costly. Is this necessary? We do an IPI TLB flush on mapping after all.

will see how i can come with a better drop

@mkroening I removed the call now. But the ipi sent on mapping flushes TLB on other cpus only if the entry is present in the page table. since we delete the entry on unmap, stale TLB can still remains on other cpus.

mkroening · 2026-08-30T17:03:38Z

+impl Deref for MappedPageBox {
+	type Target = PageRange;
+
+	fn deref(&self) -> &Self::Target {
+		&self.pages
+	}
+}


This seems non-obvious to me, since there are two types of ranges inside. If we need something like this, I'd prefer accessor methods.

mkroening · 2026-08-30T17:04:05Z

+fn page_count(pages: &PageBox) -> usize {
+	pages.len().get() / BasePageSize::SIZE as usize
+}


Please remove this helper function.

mkroening · 2026-08-30T17:04:20Z

+fn map(pages: &PageBox, phys_addr: PhysAddr, flags: PageTableEntryFlags) {
+	paging::map::<BasePageSize>(
+		VirtAddr::from(pages.start()),
+		phys_addr,
+		page_count(pages),
+		flags,
+	);
+}


Please remove this helper function.

RajeshRk18 · 2026-08-31T07:04:32Z

Thanks! Did you use any AI assistance? :)

yeah i am clearing unwanted stuff it added here!

mkroening

Thanks, this looks good to me. One more suggestion, though.

mkroening · 2026-09-06T18:13:25Z

+		})
+	}
+
+	pub fn pages(&self) -> &PageBox {


Suggested change

pub fn pages(&self) -> &PageBox {

pub fn pages(&self) -> &PageRange {

@RajeshRk18, friendly ping. :)

mkroening · 2026-09-12T08:36:07Z

Could you also add attribution to the AI coding assistants to your commits as described here? AI Coding Assistants — The Linux Kernel documentation

Assisted-by: Claude:claude-fable-5 Assisted-by: Claude:claude-fable-5-1

RajeshRk18 · 2026-10-10T18:27:32Z

@mkroening please check! And sorry i totally forgot to push the changes

mkroening

Thanks! :)

github-actions Bot added x86_64 mm aarch64 labels Aug 30, 2026

github-actions Bot reviewed Aug 30, 2026

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mkroening requested changes Aug 30, 2026

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RajeshRk18 marked this pull request as draft August 31, 2026 08:55

RajeshRk18 force-pushed the feat/mapped-page-box branch from d3ab508 to afb2fd0 Compare September 3, 2026 14:28

RajeshRk18 marked this pull request as ready for review September 3, 2026 15:06

RajeshRk18 requested a review from mkroening September 5, 2026 12:23

mkroening requested changes Sep 6, 2026

View reviewed changes

feat(mm): introduce MappedPageBox

60d883d

Assisted-by: Claude:claude-fable-5 Assisted-by: Claude:claude-fable-5-1

RajeshRk18 force-pushed the feat/mapped-page-box branch from afb2fd0 to 60d883d Compare October 10, 2026 08:30

mkroening self-requested a review October 10, 2026 09:21

mkroening approved these changes Oct 13, 2026

View reviewed changes

mkroening added this pull request to the merge queue Oct 13, 2026

Merged via the queue into hermit-os:main with commit e9d916a Oct 13, 2026
25 checks passed

	pub fn pages(&self) -> &PageBox {
	pub fn pages(&self) -> &PageRange {

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mkroening commented Sep 12, 2026

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