LKML Archive on lore.kernel.org
help / color / mirror / Atom feed
From: "Leizhen (ThunderTown)" <thunder.leizhen@huawei.com>
To: John Garry <john.garry@huawei.com>,
	Robin Murphy <robin.murphy@arm.com>,
	Will Deacon <will@kernel.org>, Joerg Roedel <joro@8bytes.org>,
	linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
	iommu <iommu@lists.linux-foundation.org>,
	<linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 1/4] iommu/arm-smmu-v3: Use command queue batching helpers to improve performance
Date: Mon, 16 Aug 2021 15:47:58 +0800	[thread overview]
Message-ID: <e8b71423-e827-f141-1203-00aca2e70834@huawei.com> (raw)
In-Reply-To: <a3cdd5df-c028-5484-ce99-928a689d341a@huawei.com>



On 2021/8/16 15:24, John Garry wrote:
>> In addition, I find that function arm_smmu_cmdq_build_cmd() can also be optimized
>> slightly, three useless instructions can be reduced.
> 
> I think that you could optimise further by pre-building commonly used commands.
> 
> For example, CMD_SYNC without MSI polling is always the same. And then only different in 1 field for MSI polling.
> 
> But you need to check if the performance gain is worth the change.

Good advice. I can give it a try.

> 
>>
>> Case 1):
>> void arm_smmu_cmdq_build_cmd_tst1(u64 *cmd, struct arm_smmu_cmdq_ent *ent)
>> {
>>          memset(cmd, 0, 1 << CMDQ_ENT_SZ_SHIFT);
>>          cmd[0] |= FIELD_PREP(CMDQ_0_OP, ent->opcode);
>> }
>> 0000000000004608 <arm_smmu_cmdq_build_cmd_tst1>:
>>      4608:       a9007c1f        stp     xzr, xzr, [x0]
>>      460c:       39400022        ldrb    w2, [x1]
>>      4610:       f9400001        ldr     x1, [x0]
>>      4614:       aa020021        orr     x1, x1, x2
>>      4618:       f9000001        str     x1, [x0]
>>      461c:       d65f03c0        ret
>>
>> Case 2):
>> void arm_smmu_cmdq_build_cmd_tst2(u64 *cmd, struct arm_smmu_cmdq_ent *ent)
>> {
>>          int i;
>>
>>          cmd[0] = FIELD_PREP(CMDQ_0_OP, ent->opcode);
>>          for (i = 1; i < CMDQ_ENT_DWORDS; i++)
>>                  cmd[i] = 0;
>> }
>> 0000000000004620 <arm_smmu_cmdq_build_cmd_tst2>:
>>      4620:       39400021        ldrb    w1, [x1]
>>      4624:       a9007c01        stp     x1, xzr, [x0]
>>      4628:       d65f03c0        ret
>>      462c:       d503201f        nop
>>
>> Case 3):
>> void arm_smmu_cmdq_build_cmd_tst3(u64 *cmd, struct arm_smmu_cmdq_ent *ent)
>> {
>>          memset(cmd, 0, 1 << CMDQ_ENT_SZ_SHIFT);
>>          cmd[0] = FIELD_PREP(CMDQ_0_OP, ent->opcode);
>> }
>> 0000000000004630 <arm_smmu_cmdq_build_cmd_tst3>:
>>      4630:       a9007c1f        stp     xzr, xzr, [x0]
>>      4634:       39400021        ldrb    w1, [x1]
>>      4638:       f9000001        str     x1, [x0]
>>      463c:       d65f03c0        ret
>>
> 
> .
> 

  reply	other threads:[~2021-08-16  7:48 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-11 11:48 [PATCH 0/4] Prepare for ECMDQ support Zhen Lei
2021-08-11 11:48 ` [PATCH 1/4] iommu/arm-smmu-v3: Use command queue batching helpers to improve performance Zhen Lei
2021-08-13 16:01   ` Robin Murphy
2021-08-13 16:45     ` John Garry
2021-08-16  2:15       ` Leizhen (ThunderTown)
2021-08-16  4:05         ` Leizhen (ThunderTown)
2021-08-16  7:24           ` John Garry
2021-08-16  7:47             ` Leizhen (ThunderTown) [this message]
2021-08-16  8:21               ` Will Deacon
2021-08-16  8:41                 ` Leizhen (ThunderTown)
2021-08-11 11:48 ` [PATCH 2/4] iommu/arm-smmu-v3: Add and use static helper function arm_smmu_cmdq_issue_cmd_with_sync() Zhen Lei
2021-08-11 11:48 ` [PATCH 3/4] iommu/arm-smmu-v3: Add and use static helper function arm_smmu_get_cmdq() Zhen Lei
2021-08-11 11:48 ` [PATCH 4/4] iommu/arm-smmu-v3: Extract reusable function __arm_smmu_cmdq_skip_err() Zhen Lei
2021-08-13 14:33 ` [PATCH 0/4] Prepare for ECMDQ support Will Deacon

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=e8b71423-e827-f141-1203-00aca2e70834@huawei.com \
    --to=thunder.leizhen@huawei.com \
    --cc=iommu@lists.linux-foundation.org \
    --cc=john.garry@huawei.com \
    --cc=joro@8bytes.org \
    --cc=linux-arm-kernel@lists.infradead.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=robin.murphy@arm.com \
    --cc=will@kernel.org \
    --subject='Re: [PATCH 1/4] iommu/arm-smmu-v3: Use command queue batching helpers to improve performance' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).