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 <[email protected]> --- 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 ac6d6df..f3a56e1 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 */ @@ -786,6 +787,11 @@ void arm_smmu_cmdq_build_sync_msi_cmd(u64 *cmd, struct arm_smmu_cmdq_ent *ent) cmd[1] = ent->sync.msiaddr & CMDQ_SYNC_1_MSIADDR_MASK; } +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) { @@ -906,6 +912,8 @@ 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"); @@ -958,9 +966,17 @@ 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_sync_msi_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_sync_msi_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 _______________________________________________ iommu mailing list [email protected] https://lists.linuxfoundation.org/mailman/listinfo/iommu
