On 21/06/2021 17:36, John Garry wrote:
Members of struct "llq" will be zero-inited, apart from member max_n_shift.
But we write llq.val straight after the init, so it was pointless to zero
init those other members. As such, separately init member max_n_shift
only.
In addition, struct "head" is initialised to "llq" only so that member
max_n_shift is set. But that member is never referenced for "head", so
remove any init there.
Removing these initializations is seen as a small performance optimisation,
as this code is (very) hot path.
Hi Will,
Any chance you can pick up this small optimisation?
Cheers
Signed-off-by: John Garry <john.ga...@huawei.com>
diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
index 54b2f27b81d4..8a8ad49bb7fd 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
@@ -727,11 +727,11 @@ static int arm_smmu_cmdq_issue_cmdlist(struct
arm_smmu_device *smmu,
unsigned long flags;
bool owner;
struct arm_smmu_cmdq *cmdq = &smmu->cmdq;
- struct arm_smmu_ll_queue llq = {
- .max_n_shift = cmdq->q.llq.max_n_shift,
- }, head = llq;
+ struct arm_smmu_ll_queue llq, head;
int ret = 0;
+ llq.max_n_shift = cmdq->q.llq.max_n_shift;
+
/* 1. Allocate some space in the queue */
local_irq_save(flags);
llq.val = READ_ONCE(cmdq->q.llq.val);
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