On Tue, Jan 27, 2015 at 12:52:12AM +0300, Sergei Rogachev wrote:
> Page owner uses the page_ext structure to keep meta-information
> for every page in the system. The structure also contains a field
> of type 'struct stack_trace', page owner uses this field during
> invocation of the function save_stack_trace. It is easy to notice
> that keeping a copy of this structure for every page in the system
> is very inefficiently in terms of memory.
>
> The patch removes this unnecessary field of page_ext and forces
> page owner to use a stack_trace structure allocated on the stack.
>
> Signed-off-by: Sergei Rogachev <rogachevser...@gmail.com>
> ---
> include/linux/page_ext.h | 2 +-
> mm/page_owner.c | 21 ++++++++++++---------
> 2 files changed, 13 insertions(+), 10 deletions(-)
>
> diff --git a/include/linux/page_ext.h b/include/linux/page_ext.h
> index d2a2c84..c42981c 100644
> --- a/include/linux/page_ext.h
> +++ b/include/linux/page_ext.h
> @@ -40,7 +40,7 @@ struct page_ext {
> #ifdef CONFIG_PAGE_OWNER
> unsigned int order;
> gfp_t gfp_mask;
> - struct stack_trace trace;
> + unsigned int nr_entries;
> unsigned long trace_entries[8];
> #endif
> };
> diff --git a/mm/page_owner.c b/mm/page_owner.c
> index 9ab4a9b..f7f3318 100644
> --- a/mm/page_owner.c
> +++ b/mm/page_owner.c
> @@ -60,19 +60,19 @@ void __reset_page_owner(struct page *page, unsigned int
> order)
> void __set_page_owner(struct page *page, unsigned int order, gfp_t gfp_mask)
> {
> struct page_ext *page_ext;
> - struct stack_trace *trace;
> + struct stack_trace trace;
>
> page_ext = lookup_page_ext(page);
>
> - trace = &page_ext->trace;
> - trace->nr_entries = 0;
> - trace->max_entries = ARRAY_SIZE(page_ext->trace_entries);
> - trace->entries = &page_ext->trace_entries[0];
> - trace->skip = 3;
> - save_stack_trace(&page_ext->trace);
> + trace.nr_entries = 0;
> + trace.max_entries = ARRAY_SIZE(page_ext->trace_entries);
> + trace.entries = &page_ext->trace_entries[0];
> + trace.skip = 3;
> + save_stack_trace(&trace);
>
> page_ext->order = order;
> page_ext->gfp_mask = gfp_mask;
> + page_ext->nr_entries = trace.nr_entries;
>
> __set_bit(PAGE_EXT_OWNER, &page_ext->flags);
> }
> @@ -83,6 +83,7 @@ print_page_owner(char __user *buf, size_t count, unsigned
> long pfn,
> {
> int ret;
> int pageblock_mt, page_mt;
> + struct stack_trace trace;
> char *kbuf;
>
> kbuf = kmalloc(count, GFP_KERNEL);
> @@ -121,8 +122,10 @@ print_page_owner(char __user *buf, size_t count,
> unsigned long pfn,
> if (ret >= count)
> goto err;
>
> - ret += snprint_stack_trace(kbuf + ret, count - ret,
> - &page_ext->trace, 0);
> + trace.nr_entries = page_ext->nr_entries;
> + trace.entries = &page_ext->trace_entries[0];
> +
> + ret += snprint_stack_trace(kbuf + ret, count - ret, &trace, 0);
> if (ret >= count)
> goto err;
Acked-by: Joonsoo Kim <iamjoonsoo....@lge.com>
Thanks.
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