2022-02-26 02:03:05

by Smita Koralahalli

Subject: [PATCH v4 1/3] x86/mce: Avoid unnecessary padding in struct mce_bank

Convert struct mce_bank member "init" from bool to a bitfield to get rid
of unnecessary padding.

Outputs collected before and after the change.

$ pahole -C mce_bank arch/x86/kernel/cpu/mce/core.o

before:

/* size: 16, cachelines: 1, members: 2 */
/* padding: 7 */
/* last cacheline: 16 bytes */

after:

/* size: 16, cachelines: 1, members: 3 */
/* last cacheline: 16 bytes */

No functional changes.

Signed-off-by: Smita Koralahalli <[email protected]>
---
Link:
https://lkml.kernel.org/r/[email protected]

v4:
Moved this patch to the first in the series.
---
arch/x86/kernel/cpu/mce/core.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/cpu/mce/core.c b/arch/x86/kernel/cpu/mce/core.c
index 728f3b36ce2d..c0e9aa9c8749 100644
--- a/arch/x86/kernel/cpu/mce/core.c
+++ b/arch/x86/kernel/cpu/mce/core.c
@@ -69,7 +69,9 @@ DEFINE_PER_CPU_READ_MOSTLY(unsigned int, mce_num_banks);

struct mce_bank {
u64 ctl; /* subevents to enable */
- bool init; /* initialise bank? */
+
+ __u64 init : 1, /* initialise bank? */
+ __reserved_1 : 63;
};
static DEFINE_PER_CPU_READ_MOSTLY(struct mce_bank[MAX_NR_BANKS], mce_banks_array);

--
2.17.1

2022-04-06 05:36:46

by tip-bot2 for Alexey Makhalov

Subject: [tip: ras/core] x86/mce: Avoid unnecessary padding in struct mce_bank

The following commit has been merged into the ras/core branch of tip:

Commit-ID: 9f1b19b977ee3cbd3fe9135ff63dbf221eac1d6a
Gitweb: https://git.kernel.org/tip/9f1b19b977ee3cbd3fe9135ff63dbf221eac1d6a
Author: Smita Koralahalli <[email protected]>
AuthorDate: Fri, 25 Feb 2022 13:33:40 -06:00
Committer: Borislav Petkov <[email protected]>
CommitterDate: Tue, 05 Apr 2022 21:23:34 +02:00

x86/mce: Avoid unnecessary padding in struct mce_bank

Convert struct mce_bank member "init" from bool to a bitfield to get rid
of unnecessary padding.

$ pahole -C mce_bank arch/x86/kernel/cpu/mce/core.o

before:

/* size: 16, cachelines: 1, members: 2 */
/* padding: 7 */
/* last cacheline: 16 bytes */

after:

/* size: 16, cachelines: 1, members: 3 */
/* last cacheline: 16 bytes */

No functional changes.

Signed-off-by: Smita Koralahalli <[email protected]>
Signed-off-by: Borislav Petkov <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
---
arch/x86/kernel/cpu/mce/core.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/cpu/mce/core.c b/arch/x86/kernel/cpu/mce/core.c
index 981496e..d775fcd 100644
--- a/arch/x86/kernel/cpu/mce/core.c
+++ b/arch/x86/kernel/cpu/mce/core.c
@@ -69,7 +69,9 @@ DEFINE_PER_CPU_READ_MOSTLY(unsigned int, mce_num_banks);

struct mce_bank {
u64 ctl; /* subevents to enable */
- bool init; /* initialise bank? */
+
+ __u64 init : 1, /* initialise bank? */
+ __reserved_1 : 63;
};
static DEFINE_PER_CPU_READ_MOSTLY(struct mce_bank[MAX_NR_BANKS], mce_banks_array);