mmc: core: complete/wait_for_completion performance

[Stefan Wahren]

Hi Jörg,

> Jörg Krause <joerg.krause at embedded.rocks> hat am 15. Dezember 2016 um 14:50 geschrieben:
> 
> 
> Hi Stefan,
> 
> On Wed, 2016-12-14 at 19:57 +0100, Stefan Wahren wrote:
> > Hi Jörg,
> > 
> 
> [snip]
> 
> > > > 
> > > > did you try cyclictest [1]?
> > > 
> > > Not yet. Not sure what to measure and which values to compare here.
> > 
> > i tought you have the vendor kernel and the mainline kernel available
> > for your platform.
> > 
> > So you could compare the both kernels.
> 
> Yes, that's right. I will have a look at this tool.
> 
> > > 
> > > > 
> > > > Beside the time for a request the amount of requests for the
> > > > complete
> > > > iperf test
> > > > would we interesting. Maybe there are retries.
> > > > 
> > > > I'm still interested in your PIO mode patches for mxs-mmc even
> > > > without clean up.
> > > 
> > > Actually, the patch does not implement a PIO mode, but drops DMA
> > > and
> > > uses polling instead. I've attached the patch.
> > 
> > Thanks. I applied it, but unfortunately this breaks SD card support
> > for my Duckbill and the kernel isn't able to mount the rootfs:
> > 
> > [    2.267073] mxs-mmc 80010000.ssp: initialized
> > [    2.272624] mxs-mmc 80010000.ssp: AC command error 0xffffff92
> 
> Sorry, I messed up the branches. I attached the correct patch which is
> working for me on Linux v4.9.

i tested the second version but there isn't any performance gain with the patch.

Duckbill with class 10 SD card
Linux 4.8 without patch

dd if=/dev/zero of=test bs=1k count=10000
10000+0 records in
10000+0 records out
10240000 bytes (10 MB) copied, 2.68934 s, 3.8 MB/s

dd if=/dev/zero of=test bs=8k count=10000
10000+0 records in
10000+0 records out
81920000 bytes (82 MB) copied, 8.24305 s, 9.9 MB/s


Duckbill with class 10 SD card
Linux 4.8 with patch

dd if=/dev/zero of=test bs=1k count=10000
10000+0 records in
10000+0 records out
10240000 bytes (10 MB) copied, 3.41193 s, 3.0 MB/s

dd if=/dev/zero of=test bs=8k count=10000
10000+0 records in
10000+0 records out
81920000 bytes (82 MB) copied, 14.4564 s, 5.7 MB/s

Additionally i get these warning during boot:

[    2.278445] mxs-mmc 80010000.ssp: initialized
[    2.283996] mxs-mmc 80010000.ssp: AC command error -110
[    2.305158] mxs-mmc 80010000.ssp: AC command error -110
[    2.322975] mxs-mmc 80010000.ssp: AC command error -110
[    2.338660] mxs-mmc 80010000.ssp: AC command error -110
[    2.344289] mxs-mmc 80010000.ssp: AC command error -110
[    2.365653] mxs-mmc 80010000.ssp: AC command error -110

Regards
Stefan

> 
> Jörg