linux-kernel - Re: [PATCH] memory tier: Remove unused default_dram_perf_ref

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Message-ID: <87y13mvo0n.fsf@yhuang6-desk2.ccr.corp.intel.com>
Date: Fri, 20 Sep 2024 14:26:48 +0800
From: "Huang, Ying" <ying.huang@...el.com>
To: Waiman Long <longman@...hat.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,  Alistair Popple
 <apopple@...dia.com>,  Dave Jiang <dave.jiang@...el.com>,
  linux-mm@...ck.org,  linux-kernel@...r.kernel.org
Subject: Re: [PATCH] memory tier: Remove unused default_dram_perf_ref_source

Hi, Waiman,

Waiman Long <longman@...hat.com> writes:

> Commit 3718c02dbd4c ("acpi, hmat: calculate abstract distance with HMAT")
> added a default_dram_perf_ref_source variable that was initialized but
> never used. This causes kmemleak to report the following memory leak:
>
> unreferenced object 0xff11000225a47b60 (size 16):
>   comm "swapper/0", pid 1, jiffies 4294761654
>   hex dump (first 16 bytes):
>     41 43 50 49 20 48 4d 41 54 00 c1 4b 7d b7 75 7c  ACPI HMAT..K}.u|
>   backtrace (crc e6d0e7b2):
>     [<ffffffff95d5afdb>] __kmalloc_node_track_caller_noprof+0x36b/0x440
>     [<ffffffff95c276d6>] kstrdup+0x36/0x60
>     [<ffffffff95dfabfa>] mt_set_default_dram_perf+0x23a/0x2c0
>     [<ffffffff9ad64733>] hmat_init+0x2b3/0x660
>     [<ffffffff95203cec>] do_one_initcall+0x11c/0x5c0
>     [<ffffffff9ac9cfc4>] do_initcalls+0x1b4/0x1f0
>     [<ffffffff9ac9d52e>] kernel_init_freeable+0x4ae/0x520
>     [<ffffffff97c789cc>] kernel_init+0x1c/0x150
>     [<ffffffff952aecd1>] ret_from_fork+0x31/0x70
>     [<ffffffff9520b18a>] ret_from_fork_asm+0x1a/0x30

Good catch!

> Fix this memory leak by removing default_dram_perf_ref_source.

We should have used that information.  So, I suggest the fix as below.
Is it OK for you?

---------------------------8<---------------------------------------
>From 32e6d70f531718cf99064a43fdffc8639aedcc5c Mon Sep 17 00:00:00 2001
From: Huang Ying <ying.huang@...el.com>
Date: Fri, 20 Sep 2024 09:47:40 +0800
Subject: [PATCH] memory tiers: use default_dram_perf_ref_source in log message

Commit 3718c02dbd4c ("acpi, hmat: calculate abstract distance with HMAT")
added a default_dram_perf_ref_source variable that was initialized but
never used. This causes kmemleak to report the following memory leak:

unreferenced object 0xff11000225a47b60 (size 16):
  comm "swapper/0", pid 1, jiffies 4294761654
  hex dump (first 16 bytes):
    41 43 50 49 20 48 4d 41 54 00 c1 4b 7d b7 75 7c  ACPI HMAT..K}.u|
  backtrace (crc e6d0e7b2):
    [<ffffffff95d5afdb>] __kmalloc_node_track_caller_noprof+0x36b/0x440
    [<ffffffff95c276d6>] kstrdup+0x36/0x60
    [<ffffffff95dfabfa>] mt_set_default_dram_perf+0x23a/0x2c0
    [<ffffffff9ad64733>] hmat_init+0x2b3/0x660
    [<ffffffff95203cec>] do_one_initcall+0x11c/0x5c0
    [<ffffffff9ac9cfc4>] do_initcalls+0x1b4/0x1f0
    [<ffffffff9ac9d52e>] kernel_init_freeable+0x4ae/0x520
    [<ffffffff97c789cc>] kernel_init+0x1c/0x150
    [<ffffffff952aecd1>] ret_from_fork+0x31/0x70
    [<ffffffff9520b18a>] ret_from_fork_asm+0x1a/0x30

This reminds us that we forget to use the performance data source
information.  So, use the variable in the error log message to help
identify the root cause of inconsistent performance number.

Fixes: 3718c02dbd4c ("acpi, hmat: calculate abstract distance with HMAT")
Signed-off-by: "Huang, Ying" <ying.huang@...el.com>
Reported-by: Waiman Long <longman@...hat.com>
---
 mm/memory-tiers.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/mm/memory-tiers.c b/mm/memory-tiers.c
index 4775b3a3dabe..0f5ba5c6e0c6 100644
--- a/mm/memory-tiers.c
+++ b/mm/memory-tiers.c
@@ -749,10 +749,10 @@ int mt_set_default_dram_perf(int nid, struct access_coordinate *perf,
 		pr_info(
 "memory-tiers: the performance of DRAM node %d mismatches that of the reference\n"
 "DRAM node %d.\n", nid, default_dram_perf_ref_nid);
-		pr_info("  performance of reference DRAM node %d:\n",
-			default_dram_perf_ref_nid);
+		pr_info("  performance of reference DRAM node %d from %s:\n",
+			default_dram_perf_ref_nid, default_dram_perf_ref_source);
 		dump_hmem_attrs(&default_dram_perf, "    ");
-		pr_info("  performance of DRAM node %d:\n", nid);
+		pr_info("  performance of DRAM node %d from %s:\n", nid, source);
 		dump_hmem_attrs(perf, "    ");
 		pr_info(
 "  disable default DRAM node performance based abstract distance algorithm.\n");
-- 
2.39.2