On Wed, Sep 27, 2017 at 2:02 PM, Adrian Hunter [off-list ref] wrote:

On 27/09/17 02:42, Linus Walleij wrote:

quoted

On Fri, Sep 22, 2017 at 2:36 PM, Adrian Hunter [off-list ref] wrote:

quoted

Until mmc has blk-mq support fully implemented and tested, add a
parameter use_blk_mq, default to false unless config option MMC_MQ_DEFAULT
is selected.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>

quoted

+config MMC_MQ_DEFAULT
+       bool "MMC: use blk-mq I/O path by default"
+       depends on MMC && BLOCK

I would say:
default y

Why not. SCSI is starting to enable this by default so IMO we should

SCSI didn't manage it yet.

quoted

not take the
intermediate step of having this as optional. Otherwise it never gets tested.

The argument that we don't have to take any responsibility for getting
things tested is a poor one.

Anyway, you can always send a patch later to change the default, so why the
hurry to do it now?

I think it should be the default so we smoke out bugs by throwing it at
users during the -rc phase and the non-mq path should be the fallback.

The -rc phase is for finding problems like this IMO.

It is partly a personality trait I guess, I'm not very cautious in general,
for good and for bad.

quoted

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+module_param_named(use_blk_mq, mmc_use_blk_mq, bool, S_IWUSR | S_IRUGO);

Are people really modprobing this so it needs to be a module parameter?

Irrespective of modprobe, the parameter can be changed without re-compiling.

quoted

Maybe I'm the only developer stupid enough to just recompile and reboot

Just change the parameter and unbind and rebind the host controller.

Ah clever. I don't do such things, I guess I should try it out.

Yours,
Linus Walleij