From: Zhen Lei <thunder.leizhen@huawei.com>
To: Robin Murphy <robin.murphy@arm.com>,
Will Deacon <will.deacon@arm.com>, Joerg Roedel <joro@8bytes.org>,
linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
iommu <iommu@lists.linux-foundation.org>,
linux-kernel <linux-kernel@vger.kernel.org>
Cc: Zhen Lei <thunder.leizhen@huawei.com>,
LinuxArm <linuxarm@huawei.com>, Hanjun Guo <guohanjun@huawei.com>,
Libin <huawei.libin@huawei.com>
Subject: [PATCH v2 2/2] iommu/arm-smmu-v3: avoid redundant CMD_SYNCs if possible
Date: Thu, 9 Aug 2018 19:48:53 +0800 [thread overview]
Message-ID: <1533815333-17320-3-git-send-email-thunder.leizhen@huawei.com> (raw)
In-Reply-To: <1533815333-17320-1-git-send-email-thunder.leizhen@huawei.com>
More than two CMD_SYNCs maybe adjacent in the command queue, and the first
one has done what others want to do. Drop the redundant CMD_SYNCs can
improve IO performance especially under the pressure scene.
I did the statistics in my test environment, the number of CMD_SYNCs can
be reduced about 1/3. See below:
CMD_SYNCs reduced: 19542181
CMD_SYNCs total: 58098548 (include reduced)
CMDs total: 116197099 (TLBI:SYNC about 1:1)
Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
---
drivers/iommu/arm-smmu-v3.c | 22 +++++++++++++++++++---
1 file changed, 19 insertions(+), 3 deletions(-)
diff --git a/drivers/iommu/arm-smmu-v3.c b/drivers/iommu/arm-smmu-v3.c
index d17a9a7..b96d2d2 100644
--- a/drivers/iommu/arm-smmu-v3.c
+++ b/drivers/iommu/arm-smmu-v3.c
@@ -567,6 +567,7 @@ struct arm_smmu_device {
int gerr_irq;
int combined_irq;
u32 sync_nr;
+ u8 prev_cmd_opcode;
unsigned long ias; /* IPA */
unsigned long oas; /* PA */
@@ -775,6 +776,11 @@ static int queue_remove_raw(struct arm_smmu_queue *q, u64 *ent)
return 0;
}
+static inline u8 arm_smmu_cmd_opcode_get(u64 *cmd)
+{
+ return cmd[0] & CMDQ_0_OP;
+}
+
/* High-level queue accessors */
static int arm_smmu_cmdq_build_cmd(u64 *cmd, struct arm_smmu_cmdq_ent *ent)
{
@@ -900,6 +906,8 @@ static void arm_smmu_cmdq_insert_cmd(struct arm_smmu_device *smmu, u64 *cmd)
struct arm_smmu_queue *q = &smmu->cmdq.q;
bool wfe = !!(smmu->features & ARM_SMMU_FEAT_SEV);
+ smmu->prev_cmd_opcode = arm_smmu_cmd_opcode_get(cmd);
+
while (queue_insert_raw(q, cmd) == -ENOSPC) {
if (queue_poll_cons(q, false, wfe))
dev_err_ratelimited(smmu->dev, "CMDQ timeout\n");
@@ -952,9 +960,17 @@ static int __arm_smmu_cmdq_issue_sync_msi(struct arm_smmu_device *smmu)
};
spin_lock_irqsave(&smmu->cmdq.lock, flags);
- ent.sync.msidata = ++smmu->sync_nr;
- arm_smmu_cmdq_build_cmd(cmd, &ent);
- arm_smmu_cmdq_insert_cmd(smmu, cmd);
+ if (smmu->prev_cmd_opcode == CMDQ_OP_CMD_SYNC) {
+ /*
+ * Previous command is CMD_SYNC also, there is no need to add
+ * one more. Just poll it.
+ */
+ ent.sync.msidata = smmu->sync_nr;
+ } else {
+ ent.sync.msidata = ++smmu->sync_nr;
+ arm_smmu_cmdq_build_cmd(cmd, &ent);
+ arm_smmu_cmdq_insert_cmd(smmu, cmd);
+ }
spin_unlock_irqrestore(&smmu->cmdq.lock, flags);
return __arm_smmu_sync_poll_msi(smmu, ent.sync.msidata);
--
1.8.3
next prev parent reply other threads:[~2018-08-09 11:50 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-08-09 11:48 [PATCH v2 0/2] bugfix and optimization about CMD_SYNC Zhen Lei
2018-08-09 11:48 ` [PATCH v2 1/2] iommu/arm-smmu-v3: fix unexpected CMD_SYNC timeout Zhen Lei
2018-08-09 11:48 ` Zhen Lei [this message]
2018-08-09 12:02 ` [PATCH v2 2/2] iommu/arm-smmu-v3: avoid redundant CMD_SYNCs if possible Robin Murphy
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