Brian, I tested this patch (rediffed against 2.5.13, below)
on the quad Xeon and it failed.
The machine died when bringing up the secondary CPUs
("CPU#3 already started!" and "Unable to handle kernel...")
I backed out the sched.c part and the machine booted. So
I guess the secondary CPU bringup code uses the scheduler
somehow.
And again, the numbers in /proc/meminfo are whacko:
LowFree: 94724 kB
SwapTotal: 4000040 kB
SwapFree: 3999700 kB
Dirty: 7232 kB
Writeback: 4294967264 kB
Which never happens with the open-coded per-cpu accumulators.
After a normal boot I see:
LowFree: 95804 kB
SwapTotal: 4000040 kB
SwapFree: 3999940 kB
Dirty: 1356 kB
Writeback: 0 kB
Now, it may be that some pages are being marked dirty before
the per-cpu areas are set up, but there's no way in which
any pages will have been marked for writeback by that time, so
that "-32" value is definitely wrong.
'fraid I have to do a whine-and-run on this problem, but
it does still appear that there is something fishy with
the percpu infrastructure.
--- 2.5.13/include/linux/page-flags.h~bgerst-pcpu Thu May 2 19:21:12 2002
+++ 2.5.13-akpm/include/linux/page-flags.h Thu May 2 19:23:11 2002
@@ -42,6 +42,8 @@
* address space...
*/
+#include <linux/percpu.h>
+
/*
* Don't use the *_dontuse flags. Use the macros. Otherwise you'll break
* locked- and dirty-page accounting. The top eight bits of page->flags are
@@ -69,18 +71,20 @@
/*
* Global page accounting. One instance per CPU.
*/
-extern struct page_state {
+struct page_state {
unsigned long nr_dirty;
unsigned long nr_writeback;
unsigned long nr_pagecache;
-} ____cacheline_aligned_in_smp page_states[NR_CPUS];
+};
+
+extern struct page_state __per_cpu_data page_states;
extern void get_page_state(struct page_state *ret);
#define mod_page_state(member, delta) \
do { \
preempt_disable(); \
- page_states[smp_processor_id()].member += (delta); \
++ this_cpu(page_states).member += (delta); \
preempt_enable(); \
} while (0)
--- 2.5.13/kernel/sched.c~bgerst-pcpu Thu May 2 19:21:12 2002
+++ 2.5.13-akpm/kernel/sched.c Thu May 2 19:21:12 2002
@@ -22,6 +22,7 @@
#include <linux/interrupt.h>
#include <linux/completion.h>
#include <linux/kernel_stat.h>
+#include <linux/percpu.h>
/*
* Priority of a process goes from 0 to 139. The 0-99
@@ -154,10 +155,18 @@ struct runqueue {
list_t migration_queue;
} ____cacheline_aligned;
-static struct runqueue runqueues[NR_CPUS] __cacheline_aligned;
+static struct runqueue __per_cpu_data runqueues;
+
+static inline struct runqueue *cpu_rq(int cpu)
+{
+ return &per_cpu(runqueues, cpu);
+}
+
+static inline struct runqueue *this_rq(void)
+{
+ return &this_cpu(runqueues);
+}
-#define cpu_rq(cpu) (runqueues + (cpu))
-#define this_rq() cpu_rq(smp_processor_id())
#define task_rq(p) cpu_rq((p)->thread_info->cpu)
#define cpu_curr(cpu) (cpu_rq(cpu)->curr)
#define rt_task(p) ((p)->prio < MAX_RT_PRIO)
--- 2.5.13/mm/page_alloc.c~bgerst-pcpu Thu May 2 19:21:12 2002
+++ 2.5.13-akpm/mm/page_alloc.c Thu May 2 19:21:12 2002
@@ -576,7 +576,7 @@ unsigned long nr_buffermem_pages(void)
* The result is unavoidably approximate - it can change
* during and after execution of this function.
*/
-struct page_state page_states[NR_CPUS] __cacheline_aligned;
+struct page_state __per_cpu_data page_states;
EXPORT_SYMBOL(page_states);
void get_page_state(struct page_state *ret)
@@ -590,7 +590,7 @@ void get_page_state(struct page_state *r
for (pcpu = 0; pcpu < smp_num_cpus; pcpu++) {
struct page_state *ps;
- ps = &page_states[cpu_logical_map(pcpu)];
+ ps = &per_cpu(page_states,cpu_logical_map(pcpu));
ret->nr_dirty += ps->nr_dirty;
ret->nr_writeback += ps->nr_writeback;
ret->nr_pagecache += ps->nr_pagecache;
--- 2.5.13/mm/page-writeback.c~bgerst-pcpu Thu May 2 19:21:12 2002
+++ 2.5.13-akpm/mm/page-writeback.c Thu May 2 19:22:25 2002
@@ -20,6 +20,7 @@
#include <linux/writeback.h>
#include <linux/init.h>
#include <linux/sysrq.h>
+#include <linux/percpu.h>
/*
* Memory thresholds, in percentages
@@ -103,15 +104,12 @@ void balance_dirty_pages(struct address_
*/
void balance_dirty_pages_ratelimited(struct address_space *mapping)
{
- static struct rate_limit_struct {
- int count;
- } ____cacheline_aligned ratelimits[NR_CPUS];
- int cpu;
+ static int __per_cpu_data ratelimits;
preempt_disable();
cpu = smp_processor_id();
- if (ratelimits[cpu].count++ >= 1000) {
- ratelimits[cpu].count = 0;
+ if (this_cpu(ratelimits)++ >= 1000) {
+ this_cpu(ratelimits) = 0;
preempt_enable();
balance_dirty_pages(mapping);
return;
--- 2.5.13/net/socket.c~bgerst-pcpu Thu May 2 19:21:12 2002
+++ 2.5.13-akpm/net/socket.c Thu May 2 19:21:12 2002
@@ -74,6 +74,7 @@
#include <linux/cache.h>
#include <linux/module.h>
#include <linux/highmem.h>
+#include <linux/percpu.h>
#if defined(CONFIG_KMOD) && defined(CONFIG_NET)
#include <linux/kmod.h>
@@ -181,10 +182,7 @@ static __inline__ void net_family_read_u
* Statistics counters of the socket lists
*/
-static union {
- int counter;
- char __pad[SMP_CACHE_BYTES];
-} sockets_in_use[NR_CPUS] __cacheline_aligned = {{0}};
+static int __per_cpu_data sockets_in_use;
/*
* Support routines. Move socket addresses back and forth across the kernel/user
@@ -498,7 +496,7 @@ struct socket *sock_alloc(void)
inode->i_uid = current->fsuid;
inode->i_gid = current->fsgid;
- sockets_in_use[smp_processor_id()].counter++;
+ this_cpu(sockets_in_use)++;
return sock;
}
@@ -530,7 +528,7 @@ void sock_release(struct socket *sock)
if (sock->fasync_list)
printk(KERN_ERR "sock_release: fasync list not empty!\n");
- sockets_in_use[smp_processor_id()].counter--;
+ this_cpu(sockets_in_use)--;
if (!sock->file) {
iput(SOCK_INODE(sock));
return;
@@ -1774,7 +1772,7 @@ int socket_get_info(char *buffer, char *
int counter = 0;
for (cpu=0; cpu<smp_num_cpus; cpu++)
- counter += sockets_in_use[cpu_logical_map(cpu)].counter;
+ counter += per_cpu(sockets_in_use,cpu_logical_map(cpu));
/* It can be negative, by the way. 8) */
if (counter < 0)
-
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