From: "Leizhen (ThunderTown)" <thunder.leizhen@huawei.com>
To: Will Deacon <will.deacon@arm.com>
Cc: Joerg Roedel <joro@8bytes.org>,
linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
iommu <iommu@lists.linux-foundation.org>,
Robin Murphy <robin.murphy@arm.com>,
linux-kernel <linux-kernel@vger.kernel.org>,
Hanjun Guo <guohanjun@huawei.com>,
Libin <huawei.libin@huawei.com>, Jinyue Li <lijinyue@huawei.com>,
Kefeng Wang <wangkefeng.wang@huawei.com>
Subject: Re: [PATCH v2 1/3] iommu/arm-smmu-v3: put off the execution of TLBI* to reduce lock confliction
Date: Thu, 19 Oct 2017 11:00:45 +0800 [thread overview]
Message-ID: <59E8155D.2070102@huawei.com> (raw)
In-Reply-To: <20171018125849.GD4077@arm.com>
On 2017/10/18 20:58, Will Deacon wrote:
> Hi Thunder,
>
> On Tue, Sep 12, 2017 at 09:00:36PM +0800, Zhen Lei wrote:
>> Because all TLBI commands should be followed by a SYNC command, to make
>> sure that it has been completely finished. So we can just add the TLBI
>> commands into the queue, and put off the execution until meet SYNC or
>> other commands. To prevent the followed SYNC command waiting for a long
>> time because of too many commands have been delayed, restrict the max
>> delayed number.
>>
>> According to my test, I got the same performance data as I replaced writel
>> with writel_relaxed in queue_inc_prod.
>>
>> Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
>> ---
>> drivers/iommu/arm-smmu-v3.c | 42 +++++++++++++++++++++++++++++++++++++-----
>> 1 file changed, 37 insertions(+), 5 deletions(-)
>
> If we want to go down the route of explicit command batching, I'd much
> rather do it by implementing the iotlb_range_add callback in the driver,
> and have a fixed-length array of batched ranges on the domain. We could
I think even if iotlb_range_add callback is implemented, this patch is still valuable. The main purpose
of this patch is to reduce dsb operation. So in the scenario with iotlb_range_add implemented:
.iotlb_range_add:
spin_lock_irqsave(&smmu->cmdq.lock, flags);
...
add tlbi range-1 to cmq-queue
...
add tlbi range-n to cmq-queue //n
dsb
...
spin_unlock_irqrestore(&smmu->cmdq.lock, flags);
.iotlb_sync
spin_lock_irqsave(&smmu->cmdq.lock, flags);
...
add cmd_sync to cmq-queue
dsb
...
spin_unlock_irqrestore(&smmu->cmdq.lock, flags);
Although iotlb_range_add can reduce n-1 dsb operations, but there are still 1 left. If n is not large enough,
this patch is helpful.
> potentially toggle this function pointer based on the compatible string too,
> if it shows only to benefit some systems.
[
On 2017/9/19 12:31, Nate Watterson wrote:
I tested these (2) patches on QDF2400 hardware and saw performance
improvements in line with those I reported when testing the original
series.
]
I'm not sure whether this patch can improve performance on QDF2400, because there are two patches. But at least
it seems harmless, maybe the other hardware platforms are the same.
>
> Will
>
> .
>
--
Thanks!
BestRegards
next prev parent reply other threads:[~2017-10-19 3:02 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-09-12 13:00 [PATCH v2 0/3] arm-smmu: performance optimization Zhen Lei
2017-09-12 13:00 ` [PATCH v2 1/3] iommu/arm-smmu-v3: put off the execution of TLBI* to reduce lock confliction Zhen Lei
2017-10-18 12:58 ` Will Deacon
2017-10-19 3:00 ` Leizhen (ThunderTown) [this message]
2017-10-19 9:12 ` Will Deacon
2017-09-12 13:00 ` [PATCH v2 2/3] iommu/arm-smmu-v3: add support for unmap an iova range with only one tlb sync Zhen Lei
2017-10-18 13:00 ` Will Deacon
2017-10-19 3:17 ` Leizhen (ThunderTown)
2017-09-12 13:00 ` [PATCH v2 3/3] iommu/arm-smmu: add support for unmap a memory " Zhen Lei
2017-09-19 4:31 ` [PATCH v2 0/3] arm-smmu: performance optimization Nate Watterson
2017-09-19 6:26 ` Leizhen (ThunderTown)
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=59E8155D.2070102@huawei.com \
--to=thunder.leizhen@huawei.com \
--cc=guohanjun@huawei.com \
--cc=huawei.libin@huawei.com \
--cc=iommu@lists.linux-foundation.org \
--cc=joro@8bytes.org \
--cc=lijinyue@huawei.com \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-kernel@vger.kernel.org \
--cc=robin.murphy@arm.com \
--cc=wangkefeng.wang@huawei.com \
--cc=will.deacon@arm.com \
/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
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
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).