Module Name: src
Committed By: chs
Date: Sun Oct 18 18:31:31 UTC 2020
Modified Files:
src/sys/uvm: uvm_page.c uvm_pgflcache.c
Log Message:
In the current code, CPU_COUNT_FREEPAGES counts pages in the global
freelists AND the per-CPU pgflcache free pages caches, and that is the
number of pages that the pagedaemon considers to be available.
However, most pages in the pgflcache per-CPU free page caches are NOT
actually available for any particular allocation, and thus allocating
a page can fail even though the pagedaemon thinks enough pages are
available. This change makes CPU_COUNT_FREEPAGES only count pages in
the global freelists and not pages in the pgflcache per-CPU free page
caches, thus better aligning the pagedaemon's view of how many pages
are available with the number of pages that can actually be allocated
by any particular request. This fixes a hang that Christos was hitting.
To generate a diff of this commit:
cvs rdiff -u -r1.248 -r1.249 src/sys/uvm/uvm_page.c
cvs rdiff -u -r1.5 -r1.6 src/sys/uvm/uvm_pgflcache.c
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/sys/uvm/uvm_page.c
diff -u src/sys/uvm/uvm_page.c:1.248 src/sys/uvm/uvm_page.c:1.249
--- src/sys/uvm/uvm_page.c:1.248 Sun Oct 18 18:22:29 2020
+++ src/sys/uvm/uvm_page.c Sun Oct 18 18:31:31 2020
@@ -1,4 +1,4 @@
-/* $NetBSD: uvm_page.c,v 1.248 2020/10/18 18:22:29 chs Exp $ */
+/* $NetBSD: uvm_page.c,v 1.249 2020/10/18 18:31:31 chs Exp $ */
/*-
* Copyright (c) 2019, 2020 The NetBSD Foundation, Inc.
@@ -95,7 +95,7 @@
*/
#include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: uvm_page.c,v 1.248 2020/10/18 18:22:29 chs Exp $");
+__KERNEL_RCSID(0, "$NetBSD: uvm_page.c,v 1.249 2020/10/18 18:31:31 chs Exp $");
#include "opt_ddb.h"
#include "opt_uvm.h"
@@ -1069,6 +1069,7 @@ uvm_pagealloc_pgb(struct uvm_cpu *ucpu,
KASSERT(pg->flags == PG_FREE);
pg->flags = PG_BUSY | PG_CLEAN | PG_FAKE;
pgb->pgb_nfree--;
+ CPU_COUNT(CPU_COUNT_FREEPAGES, -1);
/*
* While we have the bucket locked and our data
@@ -1270,7 +1271,6 @@ uvm_pagealloc_strat(struct uvm_object *o
* while still at IPL_VM, update allocation statistics.
*/
- CPU_COUNT(CPU_COUNT_FREEPAGES, -1);
if (anon) {
CPU_COUNT(CPU_COUNT_ANONCLEAN, 1);
}
@@ -1567,7 +1567,6 @@ uvm_pagefree(struct vm_page *pg)
/* Try to send the page to the per-CPU cache. */
s = splvm();
- CPU_COUNT(CPU_COUNT_FREEPAGES, 1);
ucpu = curcpu()->ci_data.cpu_uvm;
bucket = uvm_page_get_bucket(pg);
if (bucket == ucpu->pgflbucket && uvm_pgflcache_free(ucpu, pg)) {
@@ -1585,6 +1584,7 @@ uvm_pagefree(struct vm_page *pg)
pg->flags = PG_FREE;
LIST_INSERT_HEAD(&pgb->pgb_colors[VM_PGCOLOR(pg)], pg, pageq.list);
pgb->pgb_nfree++;
+ CPU_COUNT(CPU_COUNT_FREEPAGES, 1);
mutex_spin_exit(lock);
splx(s);
}
Index: src/sys/uvm/uvm_pgflcache.c
diff -u src/sys/uvm/uvm_pgflcache.c:1.5 src/sys/uvm/uvm_pgflcache.c:1.6
--- src/sys/uvm/uvm_pgflcache.c:1.5 Sun Jun 14 21:41:42 2020
+++ src/sys/uvm/uvm_pgflcache.c Sun Oct 18 18:31:31 2020
@@ -1,4 +1,4 @@
-/* $NetBSD: uvm_pgflcache.c,v 1.5 2020/06/14 21:41:42 ad Exp $ */
+/* $NetBSD: uvm_pgflcache.c,v 1.6 2020/10/18 18:31:31 chs Exp $ */
/*-
* Copyright (c) 2019 The NetBSD Foundation, Inc.
@@ -43,7 +43,7 @@
*/
#include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: uvm_pgflcache.c,v 1.5 2020/06/14 21:41:42 ad Exp $");
+__KERNEL_RCSID(0, "$NetBSD: uvm_pgflcache.c,v 1.6 2020/10/18 18:31:31 chs Exp $");
#include "opt_uvm.h"
#include "opt_multiprocessor.h"
@@ -151,6 +151,7 @@ uvm_pgflcache_fill(struct uvm_cpu *ucpu,
pg->pageq.list.le_prev = &head->lh_first;
}
pgb->pgb_nfree -= (count - pcc->count);
+ CPU_COUNT(CPU_COUNT_FREEPAGES, -(count - pcc->count));
pcc->count = count;
}
@@ -188,6 +189,7 @@ uvm_pgflcache_spill(struct uvm_cpu *ucpu
LIST_INSERT_HEAD(head, pcc->pages[pcc->count], pageq.list);
}
pgb->pgb_nfree += adj;
+ CPU_COUNT(CPU_COUNT_FREEPAGES, adj);
mutex_spin_exit(lock);
}
