Patchwork [01/11] slavio_timer: avoid structure holes spotted by pahole

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Submitter Blue Swirl
Date Aug. 7, 2011, 8:57 p.m.
Message ID <CAAu8pHu1fRJJoWB3kRhXEaTxNOgGE5bVsdQuSJ1-OfxCzL2wyA@mail.gmail.com>
Download mbox | patch
Permalink /patch/108851/
State New
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Comments

Blue Swirl - Aug. 7, 2011, 8:57 p.m.
Report from pahole on amd64 host:
struct SLAVIO_TIMERState {
	SysBusDevice               busdev;               /*     0  5648 */
	/* --- cacheline 88 boundary (5632 bytes) was 16 bytes ago --- */
	uint32_t                   num_cpus;             /*  5648     4 */

	/* XXX 4 bytes hole, try to pack */

	CPUTimerState              cputimer[17];         /*  5656   816 */
	/* --- cacheline 101 boundary (6464 bytes) was 8 bytes ago --- */
	uint32_t                   cputimer_mode;        /*  6472     4 */

	/* size: 6480, cachelines: 102 */
	/* sum members: 6472, holes: 1, sum holes: 4 */
	/* padding: 4 */
	/* last cacheline: 16 bytes */
};	/* definitions: 1 */

struct CPUTimerState {
	qemu_irq                   irq;                  /*     0     8 */
	ptimer_state *             timer;                /*     8     8 */
	uint32_t                   count;                /*    16     4 */
	uint32_t                   counthigh;            /*    20     4 */
	uint32_t                   reached;              /*    24     4 */

	/* XXX 4 bytes hole, try to pack */

	uint64_t                   limit;                /*    32     8 */
	uint32_t                   running;              /*    40     4 */

	/* size: 48, cachelines: 1 */
	/* sum members: 40, holes: 1, sum holes: 4 */
	/* padding: 4 */
	/* last cacheline: 48 bytes */
};	/* definitions: 1 */

Fix by rearranging the structures to avoid padding.

Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
---
 hw/slavio_timer.c |    6 +++---
 1 files changed, 3 insertions(+), 3 deletions(-)

Patch

From 54eae070f9056790fa41b468360d23cdd17503f4 Mon Sep 17 00:00:00 2001
Message-Id: <54eae070f9056790fa41b468360d23cdd17503f4.1312750600.git.blauwirbel@gmail.com>
From: Blue Swirl <blauwirbel@gmail.com>
Date: Sun, 7 Aug 2011 19:00:23 +0000
Subject: [PATCH 01/11] slavio_timer: avoid structure holes spotted by pahole

Report from pahole on amd64 host:
struct SLAVIO_TIMERState {
	SysBusDevice               busdev;               /*     0  5648 */
	/* --- cacheline 88 boundary (5632 bytes) was 16 bytes ago --- */
	uint32_t                   num_cpus;             /*  5648     4 */

	/* XXX 4 bytes hole, try to pack */

	CPUTimerState              cputimer[17];         /*  5656   816 */
	/* --- cacheline 101 boundary (6464 bytes) was 8 bytes ago --- */
	uint32_t                   cputimer_mode;        /*  6472     4 */

	/* size: 6480, cachelines: 102 */
	/* sum members: 6472, holes: 1, sum holes: 4 */
	/* padding: 4 */
	/* last cacheline: 16 bytes */
};	/* definitions: 1 */

struct CPUTimerState {
	qemu_irq                   irq;                  /*     0     8 */
	ptimer_state *             timer;                /*     8     8 */
	uint32_t                   count;                /*    16     4 */
	uint32_t                   counthigh;            /*    20     4 */
	uint32_t                   reached;              /*    24     4 */

	/* XXX 4 bytes hole, try to pack */

	uint64_t                   limit;                /*    32     8 */
	uint32_t                   running;              /*    40     4 */

	/* size: 48, cachelines: 1 */
	/* sum members: 40, holes: 1, sum holes: 4 */
	/* padding: 4 */
	/* last cacheline: 48 bytes */
};	/* definitions: 1 */

Fix by rearranging structures to avoid padding.

Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
---
 hw/slavio_timer.c |    6 +++---
 1 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/hw/slavio_timer.c b/hw/slavio_timer.c
index 5511313..f18c8d7 100644
--- a/hw/slavio_timer.c
+++ b/hw/slavio_timer.c
@@ -48,16 +48,16 @@  typedef struct CPUTimerState {
     qemu_irq irq;
     ptimer_state *timer;
     uint32_t count, counthigh, reached;
-    uint64_t limit;
-    // processor only
+    /* processor only */
     uint32_t running;
+    uint64_t limit;
 } CPUTimerState;
 
 typedef struct SLAVIO_TIMERState {
     SysBusDevice busdev;
     uint32_t num_cpus;
-    CPUTimerState cputimer[MAX_CPUS + 1];
     uint32_t cputimer_mode;
+    CPUTimerState cputimer[MAX_CPUS + 1];
 } SLAVIO_TIMERState;
 
 typedef struct TimerContext {
-- 
1.7.2.5