linux-kernel - Re: [PATCH 1/1] mmc: Set optimal I/O size when mmc_setip

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Date:   Fri, 25 Aug 2023 16:11:49 +0800
From:   Shawn Lin <shawn.lin@...k-chips.com>
To:     Sharp Xia (夏宇彬) <Sharp.Xia@...iatek.com>,
        "ulf.hansson@...aro.org" <ulf.hansson@...aro.org>
Cc:     shawn.lin@...k-chips.com,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "matthias.bgg@...il.com" <matthias.bgg@...il.com>,
        wsd_upstream <wsd_upstream@...iatek.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "angelogioacchino.delregno@...labora.com" 
        <angelogioacchino.delregno@...labora.com>,
        "linux-mediatek@...ts.infradead.org" 
        <linux-mediatek@...ts.infradead.org>,
        "linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>
Subject: Re: [PATCH 1/1] mmc: Set optimal I/O size when mmc_setip_queue

Hi Sharp,

On 2023/8/25 15:10, Sharp Xia (夏宇彬) wrote:
> On Thu, 2023-08-24 at 12:55 +0200, Ulf Hansson wrote:
>>   	
>> External email : Please do not click links or open attachments until
>> you have verified the sender or the content.
>>   On Fri, 18 Aug 2023 at 04:45, <Sharp.Xia@...iatek.com> wrote:
>>>
>>> From: Sharp Xia <Sharp.Xia@...iatek.com>
>>>
>>> MMC does not set readahead and uses the default VM_READAHEAD_PAGES
>>> resulting in slower reading speed.
>>> Use the max_req_size reported by host driver to set the optimal
>>> I/O size to improve performance.
>>
>> This seems reasonable to me. However, it would be nice if you could
>> share some performance numbers too - comparing before and after
>> $subject patch.
>>
>> Kind regards
>> Uffe
>>
>>>
>>> Signed-off-by: Sharp Xia <Sharp.Xia@...iatek.com>
>>> ---
>>>   drivers/mmc/core/queue.c | 1 +
>>>   1 file changed, 1 insertion(+)
>>>
>>> diff --git a/drivers/mmc/core/queue.c b/drivers/mmc/core/queue.c
>>> index b396e3900717..fc83c4917360 100644
>>> --- a/drivers/mmc/core/queue.c
>>> +++ b/drivers/mmc/core/queue.c
>>> @@ -359,6 +359,7 @@ static void mmc_setup_queue(struct mmc_queue
>> *mq, struct mmc_card *card)
>>>                  blk_queue_bounce_limit(mq->queue, BLK_BOUNCE_HIGH);
>>>          blk_queue_max_hw_sectors(mq->queue,
>>>                  min(host->max_blk_count, host->max_req_size /
>> 512));
>>> +       blk_queue_io_opt(mq->queue, host->max_req_size);
>>>          if (host->can_dma_map_merge)
>>>                  WARN(!blk_queue_can_use_dma_map_merging(mq->queue,
>>>                                                          mmc_dev(hos
>> t)),
>>> --
>>> 2.18.0
>>>
> 
> I test this patch on internal platform(kernel-5.15).

I patched this one and the test shows me a stable 11% performance drop.

Before:
echo 3 > proc/sys/vm/drop_caches && dd if=/data/1GB.img of=/dev/null 

2048000+0 records in
2048000+0 records out
1048576000 bytes (0.9 G) copied, 3.912249 s, 256 M/s

After:
echo 3 > proc/sys/vm/drop_caches && dd if=/data/1GB.img of=/dev/null
2048000+0 records in
2048000+0 records out
1048576000 bytes (0.9 G) copied, 4.436271 s, 225 M/s

> 
> Before:
> console:/ # echo 3 > /proc/sys/vm/drop_caches
> console:/ # dd if=/mnt/media_rw/8031-130D/super.img of=/dev/null
> 4485393+1 records in
> 4485393+1 records out
> 2296521564 bytes (2.1 G) copied, 37.124446 s, 59 M/s
> console:/ # cat /sys/block/mmcblk0/queue/read_ahead_kb
> 128
> 
> After:
> console:/ # echo 3 > /proc/sys/vm/drop_caches
> console:/ # dd if=/mnt/media_rw/8031-130D/super.img of=/dev/null
> 4485393+1 records in
> 4485393+1 records out
> 2296521564 bytes (2.1 G) copied, 28.956049 s, 76 M/s
> console:/ # cat /sys/block/mmcblk0/queue/read_ahead_kb
> 1024
>