[PATCH][2/6] CPU Hotplug mm/

From: Zwane Mwaikambo (zwane@holomorphy.com)
Date: Mon Feb 03 2003 - 06:35:03 EST


 page-writeback.c | 1 +
 page_alloc.c | 3 ++-
 slab.c | 33 ++++++++++++++++++++++++++++++++-
 vmscan.c | 42 ++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 77 insertions(+), 2 deletions(-)

Index: linux-2.5.59-lch2/mm/page-writeback.c
===================================================================
RCS file: /build/cvsroot/linux-2.5.59/mm/page-writeback.c,v
retrieving revision 1.1.1.1
diff -u -r1.1.1.1 page-writeback.c
--- linux-2.5.59-lch2/mm/page-writeback.c 17 Jan 2003 11:16:41 -0000 1.1.1.1
+++ linux-2.5.59-lch2/mm/page-writeback.c 21 Jan 2003 04:48:29 -0000
@@ -350,6 +350,7 @@
 static int
 ratelimit_handler(struct notifier_block *self, unsigned long u, void *v)
 {
+ /* This should be fine for all cases */
         set_ratelimit();
         return 0;
 }
Index: linux-2.5.59-lch2/mm/slab.c
===================================================================
RCS file: /build/cvsroot/linux-2.5.59/mm/slab.c,v
retrieving revision 1.1.1.1
diff -u -r1.1.1.1 slab.c
--- linux-2.5.59-lch2/mm/slab.c 17 Jan 2003 11:16:41 -0000 1.1.1.1
+++ linux-2.5.59-lch2/mm/slab.c 3 Feb 2003 11:14:50 -0000
@@ -528,6 +528,16 @@
         }
 }
 
+static void stop_cpu_timer(int cpu)
+{
+ struct timer_list *rt = &reap_timers[cpu];
+
+ if (rt->function) {
+ del_timer_sync(rt);
+ rt->function = NULL;
+ }
+}
+
 /*
  * Note: if someone calls kmem_cache_alloc() on the new
  * cpu before the cpuup callback had a chance to allocate
@@ -584,6 +594,24 @@
                 }
                 up(&cache_chain_sem);
                 break;
+
+ case CPU_DEAD:
+ down(&cache_chain_sem);
+ list_for_each(p, &cache_chain) {
+ struct array_cache *nc;
+
+ kmem_cache_t* cachep = list_entry(p, kmem_cache_t, next);
+ spin_lock_irq(&cachep->spinlock);
+ nc = cachep->array[cpu];
+ cachep->array[cpu] = NULL;
+ cachep->free_limit = (num_online_cpus())*cachep->batchcount
+ + cachep->num;
+ kfree(nc);
+ spin_unlock_irq(&cachep->spinlock);
+ }
+ up(&cache_chain_sem);
+ stop_cpu_timer(cpu);
+ break;
         }
         return NOTIFY_OK;
 bad:
@@ -591,7 +619,7 @@
         return NOTIFY_BAD;
 }
 
-static struct notifier_block cpucache_notifier = { &cpuup_callback, NULL, 0 };
+static struct notifier_block __devinitdata cpucache_notifier = { &cpuup_callback, NULL, 0 };
 
 static inline void ** ac_entry(struct array_cache *ac)
 {
@@ -1236,6 +1264,9 @@
         }
         {
                 int i;
+ /* no cpu_online check required here since we clear the percpu
+ * array on cpu offline and set this to NULL.
+ */
                 for (i = 0; i < NR_CPUS; i++)
                         kfree(cachep->array[i]);
                 /* NUMA: free the list3 structures */
Index: linux-2.5.59-lch2/mm/vmscan.c
===================================================================
RCS file: /build/cvsroot/linux-2.5.59/mm/vmscan.c,v
retrieving revision 1.1.1.1
retrieving revision 1.1.1.1.2.1
diff -u -r1.1.1.1 -r1.1.1.1.2.1
--- linux-2.5.59-lch2/mm/vmscan.c 17 Jan 2003 11:16:41 -0000 1.1.1.1
+++ linux-2.5.59-lch2/mm/vmscan.c 20 Jan 2003 13:48:28 -0000 1.1.1.1.2.1
@@ -27,6 +27,7 @@
 #include <linux/pagevec.h>
 #include <linux/backing-dev.h>
 #include <linux/rmap-locking.h>
+#include <linux/notifier.h>
 
 #include <asm/pgalloc.h>
 #include <asm/tlbflush.h>
@@ -931,6 +932,7 @@
         daemonize();
         set_cpus_allowed(tsk, __node_to_cpu_mask(pgdat->node_id));
         sprintf(tsk->comm, "kswapd%d", pgdat->node_id);
+ printk("Set %s affinity to %08lX\n", tsk->comm, tsk->cpus_allowed);
         sigfillset(&tsk->blocked);
         
         /*
@@ -999,6 +1001,45 @@
 }
 #endif
 
+/* It's optimal to keep kswapds on the same CPUs as their memory, but
+ not required for correctness. So if the last cpu in a node goes
+ away, let them run anywhere, and as the first one comes back,
+ restore their cpu bindings. */
+static int __devinit cpu_callback(struct notifier_block *nfb,
+ unsigned long action,
+ void *hcpu)
+{
+ pg_data_t *pgdat;
+ unsigned int hotcpu = (unsigned long)hcpu;
+ unsigned long mask;
+
+ if (action == CPU_OFFLINE) {
+ /* Make sure that kswapd never becomes unschedulable. */
+ for_each_pgdat(pgdat) {
+ mask = __node_to_cpu_mask(pgdat->node_id);
+ if (any_online_cpu(mask) < 0) {
+ mask = ~0UL;
+ set_cpus_allowed(pgdat->kswapd, mask);
+ }
+ }
+ }
+
+ if (action == CPU_ONLINE) {
+ for_each_pgdat(pgdat) {
+ mask = __node_to_cpu_mask(pgdat->node_id);
+ mask &= ~(1UL << hotcpu);
+ if (any_online_cpu(mask) < 0) {
+ mask |= (1UL << hotcpu);
+ /* One of our CPUs came back: restore mask */
+ set_cpus_allowed(pgdat->kswapd, mask);
+ }
+ }
+ }
+ return NOTIFY_OK;
+}
+
+static struct notifier_block cpu_nfb = { &cpu_callback, NULL, 0 };
+
 static int __init kswapd_init(void)
 {
         pg_data_t *pgdat;
@@ -1006,6 +1047,7 @@
         for_each_pgdat(pgdat)
                 kernel_thread(kswapd, pgdat, CLONE_KERNEL);
         total_memory = nr_free_pagecache_pages();
+ register_cpu_notifier(&cpu_nfb);
         return 0;
 }
 

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