From 9326bf8d0df3dc8033766d32c3244f26a890b9a8 Mon Sep 17 00:00:00 2001 From: mpi Date: Sun, 18 Aug 2024 08:18:49 +0000 Subject: [PATCH] Do not cache pages belonging to memory ranges with a `use' count. Such pages belong to the DMA or ISA memory ranges and caching them accelerate their exhaustion. On amd64, at least, the kernel relies on having low pages available at any time and cannot recover from their exhaustion. Should prevent livelocks reported by jsg@ and tb@ on amd64. ok deraadt@ --- sys/uvm/uvm_pmemrange.c | 13 ++++++++++++- 1 file changed, 12 insertions(+), 1 deletion(-) diff --git a/sys/uvm/uvm_pmemrange.c b/sys/uvm/uvm_pmemrange.c index 04abd46fe77..0830fd49875 100644 --- a/sys/uvm/uvm_pmemrange.c +++ b/sys/uvm/uvm_pmemrange.c @@ -1,4 +1,4 @@ -/* $OpenBSD: uvm_pmemrange.c,v 1.66 2024/05/01 12:54:27 mpi Exp $ */ +/* $OpenBSD: uvm_pmemrange.c,v 1.67 2024/08/18 08:18:49 mpi Exp $ */ /* * Copyright (c) 2024 Martin Pieuchot @@ -2303,8 +2303,19 @@ uvm_pmr_cache_put(struct vm_page *pg) { struct uvm_pmr_cache *upc = &curcpu()->ci_uvm; struct uvm_pmr_cache_item *upci; + struct uvm_pmemrange *pmr; int s; + /* + * Always give back low pages to the allocator to not accelerate + * their exhaustion. + */ + pmr = uvm_pmemrange_find(atop(VM_PAGE_TO_PHYS(pg))); + if (pmr->use > 0) { + uvm_pmr_freepages(pg, 1); + return; + } + s = splvm(); upci = &upc->upc_magz[upc->upc_actv]; if (upci->upci_npages >= UVM_PMR_CACHEMAGSZ) { -- 2.20.1