Messages in this thread Patch in this message |  | | Date | Sat, 04 May 2002 21:08:34 -0700 | From | Andrew Morton <> | Subject | Re: [PATCH] percpu updates |
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Brian Gerst wrote: > > These patches convert some of the existing arrays based on NR_CPUS to > use the new per cpu code. >
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) - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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