From: John Garry <john.garry@huawei.com>
To: <will@kernel.org>, <robin.murphy@arm.com>
Cc: <joro@8bytes.org>, <linux-arm-kernel@lists.infradead.org>,
<iommu@lists.linux-foundation.org>,
<linux-kernel@vger.kernel.org>, <linuxarm@huawei.com>,
John Garry <john.garry@huawei.com>
Subject: [PATCH] iommu/arm-smmu-v3: Remove some unneeded init in arm_smmu_cmdq_issue_cmdlist()
Date: Tue, 22 Jun 2021 00:36:34 +0800 [thread overview]
Message-ID: <1624293394-202509-1-git-send-email-john.garry@huawei.com> (raw)
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.
Signed-off-by: John Garry <john.garry@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);
--
2.26.2
next reply other threads:[~2021-06-21 16:46 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-21 16:36 John Garry [this message]
2021-08-05 10:22 ` [PATCH] iommu/arm-smmu-v3: Remove some unneeded init in arm_smmu_cmdq_issue_cmdlist() John Garry
2021-08-05 11:21 ` Will Deacon
2021-08-05 11:24 ` Robin Murphy
2021-08-05 12:18 ` Robin Murphy
2021-08-05 13:40 ` John Garry
2021-08-05 14:41 ` Robin Murphy
2021-08-05 15:16 ` John Garry
2021-08-05 17:14 ` Robin Murphy
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