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//! Early global allocator construction.
pub(crate) fn init_allocator() {
use ax_hal::mem::{MemRegionFlags, memory_regions, phys_to_virt};
info!("Initialize global memory allocator...");
info!(" use {} allocator.", ax_alloc::global_allocator().name());
// The page allocator (which backs user-space page population via
// `alloc_pages`) is initialized from a single contiguous region by
// `global_init`; every other free region is handed to the byte/heap
// allocator by `global_add_memory` (the bitmap page allocator does not
// support `add_memory`). So the region chosen for `global_init` *is* the
// entire pool available for user memory.
//
// Pick the LARGEST free region for the page allocator. Platforms with a
// single contiguous RAM region (x86/aarch64/riscv64 qemu-virt) are
// unaffected (largest == the only region). Platforms with disjoint regions
// (loongarch64 qemu-virt: a small ~248 MB low region below the MMIO hole
// plus the multi-GB high region at 0x8000_0000) previously picked the small
// low region — the "first free region after .bss" heuristic — which capped
// all user allocations at ~248 MB regardless of total RAM, OOM'ing large
// workloads (e.g. the gradle build JVM) even with gigabytes free.
let mut max_region_size = 0;
let mut max_region_paddr = 0.into();
for region in memory_regions() {
if region.flags.contains(MemRegionFlags::FREE) && region.size > max_region_size {
max_region_size = region.size;
max_region_paddr = region.paddr;
}
}
for region in memory_regions() {
if region.flags.contains(MemRegionFlags::FREE) && region.paddr == max_region_paddr {
ax_alloc::global_init(phys_to_virt(region.paddr).as_usize(), region.size)
.expect("initialize global allocator failed");
break;
}
}
for region in memory_regions() {
if region.flags.contains(MemRegionFlags::FREE) && region.paddr != max_region_paddr {
ax_alloc::global_add_memory(phys_to_virt(region.paddr).as_usize(), region.size)
.expect("add heap memory region failed");
}
}
}