linux-kernel - [PATCH 2/2] mm, page_owner: Skip unnecessary stack

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Date:   Wed, 30 Aug 2017 13:02:23 +0530
From:   Prakash Gupta <guptap@...eaurora.org>
To:     akpm@...ux-foundation.org, mhocko@...e.com, vbabka@...e.cz,
        will.deacon@....com, catalin.marinas@....com,
        iamjoonsoo.kim@....com, rmk+kernel@....linux.org.uk,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org
Cc:     Prakash Gupta <guptap@...eaurora.org>
Subject: [PATCH 2/2] mm, page_owner: Skip unnecessary stack_trace entries

The page_owner stacktrace always begin as follows:

[<ffffff987bfd48f4>] save_stack+0x40/0xc8
[<ffffff987bfd4da8>] __set_page_owner+0x3c/0x6c

These two entries do not provide any useful information and limits the
available stacktrace depth.  The page_owner stacktrace was skipping caller
function from stack entries but this was missed with commit f2ca0b557107
("mm/page_owner: use stackdepot to store stacktrace")

Example page_owner entry after the patch:

Page allocated via order 0, mask 0x8(ffffff80085fb714)
PFN 654411 type Movable Block 639 type CMA Flags 0x0(ffffffbe5c7f12c0)
[<ffffff9b64989c14>] post_alloc_hook+0x70/0x80
...
[<ffffff9b651216e8>] msm_comm_try_state+0x5f8/0x14f4
[<ffffff9b6512486c>] msm_vidc_open+0x5e4/0x7d0
[<ffffff9b65113674>] msm_v4l2_open+0xa8/0x224

Fixes: f2ca0b557107 ("mm/page_owner: use stackdepot to store stacktrace")
Signed-off-by: Prakash Gupta <guptap@...eaurora.org>
---
 mm/page_owner.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/page_owner.c b/mm/page_owner.c
index 10d16fc45bd9..75b7c39bf1df 100644
--- a/mm/page_owner.c
+++ b/mm/page_owner.c
@@ -139,7 +139,7 @@ static noinline depot_stack_handle_t save_stack(gfp_t flags)
 		.nr_entries = 0,
 		.entries = entries,
 		.max_entries = PAGE_OWNER_STACK_DEPTH,
-		.skip = 0
+		.skip = 2
 	};
 	depot_stack_handle_t handle;
 
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