linux-kernel - Re: [PATCH v2] riscv: enable THP

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Message-ID: <4037b310-47c4-ca30-d4b6-a284e87da437@microchip.com>
Date:   Mon, 29 Aug 2022 17:27:48 +0000
From:   <Conor.Dooley@...rochip.com>
To:     <jszhang@...nel.org>
CC:     <paul.walmsley@...ive.com>, <palmer@...belt.com>,
        <aou@...s.berkeley.edu>, <linux-riscv@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <ajones@...tanamicro.com>
Subject: Re: [PATCH v2] riscv: enable THP_SWAP for RV64

On 29/08/2022 15:10, Jisheng Zhang wrote:
> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
> 
> On Sat, Aug 27, 2022 at 09:13:03PM +0000, Conor.Dooley@...rochip.com wrote:
>> Hey Jisheng,
> 
> Hi Conor,
> 
>> On 27/08/2022 10:58, Jisheng Zhang wrote:
>>> I have a Sipeed Lichee RV dock board which only has 512MB DDR, so
>>> memory optimizations such as swap on zram are helpful. As is seen
>>> in commit d0637c505f8a ("arm64: enable THP_SWAP for arm64") and
>>> commit bd4c82c22c367e ("mm, THP, swap: delay splitting THP after
>>> swapped out"), THP_SWAP can improve the swap throughput significantly.
>>>
>>> Enable THP_SWAP for RV64, testing the micro-benchmark which is
>>> introduced by commit d0637c505f8a ("arm64: enable THP_SWAP for arm64")
>>> shows below numbers on the Lichee RV dock board:
>>>
>>> thp swp throughput w/o patch: 66908 bytes/ms (mean of 10 tests)
>>> thp swp throughput w/ patch: 322638 bytes/ms (mean of 10 tests)
>>
>> I know the original commit message contains this, but it's a little
>> odd. If the patch /enables/ THP then how would there be THP swap
>> prior to the patch?
> 
> hmm, it's swap I'll send a v3 to correct the description.
> 
>>
>>>
>>> Improved by 382%!
>>
>> I could not replicate the after numbers on my nezha, so I suspect
>> I am missing something in my config/setup. zswap is enabled and is
> 
> swap on zram rather than zswap ;)

I think I tried about 30 different config variations, initially not
using zswap and later using it.
My zramctl looks like so (although I did try zstd too) after running
the demo application from that commit:

NAME       ALGORITHM DISKSIZE DATA COMPR TOTAL STREAMS MOUNTPOINT
/dev/zram0 lzo-rle       241M  22M  8.4M  9.1M       1 [SWAP]

I am using the default riscv defconfig + the following:
CONFIG_ZRAM=y
CONFIG_CRYPTO_DEFLATE=y
CONFIG_CRYPTO_LZO=y
CONFIG_CRYPTO_ZSTD=y
CONFIG_ZRAM_MEMORY_TRACKING=y
CONFIG_TRANSPARENT_HUGEPAGE=y
CONFIG_TRANSPARENT_HUGEPAGE_MADVISE=y
CONFIG_THP_SWAP=y

Am I just missing something obvious here?
Sorry,
Conor.