From: Timur Tabi <timur@codeaurora.org>
To: Will Deacon <will.deacon@arm.com>,
Ganesh Mahendran <opensource.ganesh@gmail.com>
Cc: catalin.marinas@arm.com, stable@vger.kernel.org,
linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org, tchalamarla@cavium.com,
rrichter@cavium.com, apinski@cavium.com,
Shanker Donthineni <shankerd@codeaurora.org>
Subject: Re: [PATCH] Revert "arm64: Increase the max granular size"
Date: Wed, 16 Mar 2016 08:06:22 -0500 [thread overview]
Message-ID: <56E95A4E.4050709@codeaurora.org> (raw)
In-Reply-To: <20160316100759.GA18387@arm.com>
Will Deacon wrote:
> [adding Cavium folk and Timur]
>
> On Wed, Mar 16, 2016 at 05:32:23PM +0800, Ganesh Mahendran wrote:
>> Reverts commit 97303480753e ("arm64: Increase the max granular size").
>>
>> The commit 97303480753e ("arm64: Increase the max granular size") will
>> degrade system performente in some cpus.
>>
>> We test wifi network throughput with iperf on Qualcomm msm8996 CPU:
>> ----------------
>> run on host:
>> # iperf -s
>> run on device:
>> # iperf -c <device-ip-addr> -t 100 -i 1
>> ----------------
>>
>> Test result:
>> ----------------
>> with commit 97303480753e ("arm64: Increase the max granular size"):
>> 172MBits/sec
>>
>> without commit 97303480753e ("arm64: Increase the max granular size"):
>> 230MBits/sec
>> ----------------
>>
>> Some module like slab/net will use the L1_CACHE_SHIFT, so if we do not
>> set the parameter correctly, it may affect the system performance.
>>
>> So revert the commit.
>
> Unfortunately, the original patch is required to support the 128-byte L1
> cache lines of Cavium ThunderX, so we can't simply revert it like this.
> Similarly, the desire for a single, multiplatform kernel image prevents
> us from reasonably fixing this at compile time to anything other than
> the expected maximum value.
>
> Furthermore, Timur previously said that the change is also required
> "on our [Qualcomm] silicon", but I'm not sure if this is msm9886 or not:
>
> http://lkml.kernel.org/r/CAOZdJXUiRMAguDV+HEJqPg57MyBNqEcTyaH+ya=U93NHb-pdJA@mail.gmail.com
I was talking about our server part, the QDF2432. At the time, I wasn't
allowed to mention it by name.
> You could look into making ARCH_DMA_MINALIGN a runtime value, but that
> looks like an uphill struggle to me. Alternatively, we could only warn
> if the CWG is bigger than L1_CACHE_BYTES *and* we have a non-coherent
> DMA master, but that doesn't solve any performance issues from having
> things like locks sharing cachelines, not that I think we ever got any
> data on that (afaik, we don't pad locks to cacheline boundaries anyway).
> I'm also not sure what it would mean for PCI NoSnoop transactions.
Our internal version of this patch made it a Kconfig option. Perhaps
that would at least be an improvement over just reverting it? We
already have to have our own defconfig for the QDF2432.
--
Sent by an employee of the Qualcomm Innovation Center, Inc.
The Qualcomm Innovation Center, Inc. is a member of the
Code Aurora Forum, hosted by The Linux Foundation.
next prev parent reply other threads:[~2016-03-16 13:07 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-03-16 9:32 [PATCH] Revert "arm64: Increase the max granular size" Ganesh Mahendran
2016-03-16 10:07 ` Will Deacon
2016-03-16 13:06 ` Timur Tabi [this message]
2016-03-16 14:03 ` Mark Rutland
2016-03-16 14:35 ` Will Deacon
2016-03-16 14:54 ` Mark Rutland
2016-03-16 14:18 ` Catalin Marinas
2016-03-16 15:26 ` Timur Tabi
2016-03-17 14:27 ` Catalin Marinas
2016-03-17 14:49 ` Timur Tabi
2016-03-17 15:37 ` Catalin Marinas
2016-03-17 16:03 ` Marc Zyngier
2016-03-17 18:07 ` Andrew Pinski
2016-03-17 18:34 ` Timur Tabi
2016-03-17 18:37 ` Catalin Marinas
2016-03-18 21:05 ` Chalamarla, Tirumalesh
2016-03-21 1:56 ` Ganesh Mahendran
2016-03-21 17:14 ` Catalin Marinas
2016-03-21 17:23 ` Will Deacon
2016-03-21 17:33 ` Catalin Marinas
2016-03-21 17:39 ` Chalamarla, Tirumalesh
[not found] ` <CAPub14-sFgx=oCHzJPb9h9b_V0rbn5UAMDNJ-yTkjhz38JPqMQ@mail.gmail.com>
[not found] ` <10fef112-37f1-0a1b-b5af-435acd032f01@codeaurora.org>
2017-04-06 7:22 ` Imran Khan
2017-04-06 15:58 ` Catalin Marinas
2017-04-07 2:06 ` Ganesh Mahendran
2017-04-07 8:59 ` Catalin Marinas
2017-04-12 5:13 ` Imran Khan
2017-04-12 14:00 ` Chalamarla, Tirumalesh
2017-04-17 7:35 ` Imran Khan
2017-04-17 10:38 ` Sunil Kovvuri
2017-04-18 14:48 ` Catalin Marinas
2017-04-18 17:05 ` Sunil Kovvuri
2017-04-19 12:01 ` Catalin Marinas
2017-04-19 13:11 ` Sunil Kovvuri
2017-04-25 6:42 ` Ding Tianhong
2017-04-18 18:21 ` Chalamarla, Tirumalesh
2017-04-11 4:40 ` Jon Masters
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