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;
--
1.9.1
--
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