Re: [PATCH] percpu updates

Rusty Russell (rusty@rustcorp.com.au)
Mon, 6 May 2002 17:27:41 +1000


On Sat, 04 May 2002 21:08:34 -0700
Andrew Morton <akpm@zip.com.au> wrote:

> And again, the numbers in /proc/meminfo are whacko:
>
> LowFree: 94724 kB
> SwapTotal: 4000040 kB
> SwapFree: 3999700 kB
> Dirty: 7232 kB
> Writeback: 4294967264 kB

Hmmm.... I've just applied the page-flags.h and page_alloc.c changes,
and I don't get this problem at all on my 2xi386 box on 2.5.13. I
even changed the name of "page_states" to "xpage_states" to find any
other references, and inserted a BUG() if it was being dereferenced
before per-cpu offsets were initialized.

Here's the diff: do you see problems when booting with this?
Rusty.

-- 
   there are those who do and those who hang on and you don't see too
   many doers quoting their contemporaries.  -- Larry McVoy

diff -urN -I \$.*\$ --exclude TAGS -X /home/rusty/current-dontdiff --minimal linux-2.5.13/include/asm-generic/percpu.h working-2.5.13-page-per-cpu/include/asm-generic/percpu.h --- linux-2.5.13/include/asm-generic/percpu.h Mon Apr 15 11:47:44 2002 +++ working-2.5.13-page-per-cpu/include/asm-generic/percpu.h Mon May 6 17:00:55 2002 @@ -5,6 +5,7 @@ #include <linux/compiler.h> extern unsigned long __per_cpu_offset[NR_CPUS]; +extern int per_cpu_areas_done; /* var is in discarded region: offset to particular copy we want */ #define per_cpu(var, cpu) (*RELOC_HIDE(&var, __per_cpu_offset[cpu])) diff -urN -I \$.*\$ --exclude TAGS -X /home/rusty/current-dontdiff --minimal linux-2.5.13/include/linux/page-flags.h working-2.5.13-page-per-cpu/include/linux/page-flags.h --- linux-2.5.13/include/linux/page-flags.h Mon May 6 11:12:01 2002 +++ working-2.5.13-page-per-cpu/include/linux/page-flags.h Mon May 6 17:01:43 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 +71,21 @@ /* * 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 xpage_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); \ + if (!per_cpu_areas_done) BUG(); \ + this_cpu(xpage_states).member += (delta); \ preempt_enable(); \ } while (0) diff -urN -I \$.*\$ --exclude TAGS -X /home/rusty/current-dontdiff --minimal linux-2.5.13/init/main.c working-2.5.13-page-per-cpu/init/main.c --- linux-2.5.13/init/main.c Wed May 1 15:09:29 2002 +++ working-2.5.13-page-per-cpu/init/main.c Mon May 6 16:55:22 2002 @@ -278,6 +278,7 @@ #ifdef __GENERIC_PER_CPU unsigned long __per_cpu_offset[NR_CPUS]; +int per_cpu_areas_done; static void __init setup_per_cpu_areas(void) { @@ -297,6 +298,7 @@ __per_cpu_offset[i] = ptr - __per_cpu_start; memcpy(ptr, __per_cpu_start, size); } + per_cpu_areas_done = 1; } #endif /* !__GENERIC_PER_CPU */ diff -urN -I \$.*\$ --exclude TAGS -X /home/rusty/current-dontdiff --minimal linux-2.5.13/mm/page_alloc.c working-2.5.13-page-per-cpu/mm/page_alloc.c --- linux-2.5.13/mm/page_alloc.c Mon May 6 11:12:01 2002 +++ working-2.5.13-page-per-cpu/mm/page_alloc.c Mon May 6 17:02:20 2002 @@ -576,8 +576,8 @@ * The result is unavoidably approximate - it can change * during and after execution of this function. */ -struct page_state page_states[NR_CPUS] __cacheline_aligned; -EXPORT_SYMBOL(page_states); +struct page_state __per_cpu_data xpage_states; +EXPORT_SYMBOL(xpage_states); void get_page_state(struct page_state *ret) { @@ -590,7 +590,7 @@ for (pcpu = 0; pcpu < smp_num_cpus; pcpu++) { struct page_state *ps; - ps = &page_states[cpu_logical_map(pcpu)]; + ps = &per_cpu(xpage_states,cpu_logical_map(pcpu)); ret->nr_dirty += ps->nr_dirty; ret->nr_writeback += ps->nr_writeback; ret->nr_pagecache += ps->nr_pagecache; - 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/