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Subject: Re: [f2fs-dev] [PATCH v3] f2fs: change virtual mapping way for
 compression pages
From:   Chao Yu <yuchao0@huawei.com>
To:     Daeho Jeong <daeho43@gmail.com>, <linux-kernel@vger.kernel.org>,
        <linux-f2fs-devel@lists.sourceforge.net>, <kernel-team@android.com>
CC:     Daeho Jeong <daehojeong@google.com>
References: <20200812051711.2147716-1-daeho43@gmail.com>
 <b201452d-b1dd-146c-3a1a-c199d9a5974c@huawei.com>
Message-ID: <f7de60a9-c1bc-1c45-1d1e-e6c79406a387@huawei.com>
Date:   Fri, 4 Sep 2020 15:11:26 +0800
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Hi Daeho,

Could you please clean up a bit on this patch, we can wrap vm_map_ram
loop logic into f2fs_vmap() as below:

f2fs_vmap()
{
	for (i = 0; i < MAX_VMAP_RETRIES; i++) {
		cc->cbuf = vm_map_ram(cc->cpages, cc->nr_cpages, -1);
		if (cc->cbuf)
			break;
		vm_unmap_aliases();
	}
}

How do you think of this?

Thanks,

On 2020/8/13 17:09, Chao Yu wrote:
> On 2020/8/12 13:17, Daeho Jeong wrote:
>> From: Daeho Jeong <daehojeong@google.com>
>>
>> By profiling f2fs compression works, I've found vmap() callings have
>> unexpected hikes in the execution time in our test environment and
>> those are bottlenecks of f2fs decompression path. Changing these with
>> vm_map_ram(), we can enhance f2fs decompression speed pretty much.
>>
>> [Verification]
>> Android Pixel 3(ARM64, 6GB RAM, 128GB UFS)
>> Turned on only 0-3 little cores(at 1.785GHz)
>>
>> dd if=/dev/zero of=dummy bs=1m count=1000
>> echo 3 > /proc/sys/vm/drop_caches
>> dd if=dummy of=/dev/zero bs=512k
>>
>> - w/o compression -
>> 1048576000 bytes (0.9 G) copied, 2.082554 s, 480 M/s
>> 1048576000 bytes (0.9 G) copied, 2.081634 s, 480 M/s
>> 1048576000 bytes (0.9 G) copied, 2.090861 s, 478 M/s
>>
>> - before patch -
>> 1048576000 bytes (0.9 G) copied, 7.407527 s, 135 M/s
>> 1048576000 bytes (0.9 G) copied, 7.283734 s, 137 M/s
>> 1048576000 bytes (0.9 G) copied, 7.291508 s, 137 M/s
>>
>> - after patch -
>> 1048576000 bytes (0.9 G) copied, 1.998959 s, 500 M/s
>> 1048576000 bytes (0.9 G) copied, 1.987554 s, 503 M/s
>> 1048576000 bytes (0.9 G) copied, 1.986380 s, 503 M/s
>>
>> Signed-off-by: Daeho Jeong <daehojeong@google.com>
> 
> Reviewed-by: Chao Yu <yuchao0@huawei.com>
> 
> Thanks,
> 
> 
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