Re: [PATCH 1/1] mmc: Set optimal I/O size when mmc_setip_queue

[Shawn Lin]

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@xxxxxxxxxxxx> wrote:
> > > From: Sharp Xia <Sharp.Xia@xxxxxxxxxxxx>
> > >
> > > 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@xxxxxxxxxxxx>
> > > ---
> > >   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