RE: [PATCH V9 09/15] mmc: core: Add parameter use_blk_mq

[Avri Altman]

> -----Original Message-----
> From: linux-mmc-owner@xxxxxxxxxxxxxxx [mailto:linux-mmc-
> owner@xxxxxxxxxxxxxxx] On Behalf Of Linus Walleij
> Sent: Wednesday, September 27, 2017 2:42 AM
> To: Adrian Hunter <adrian.hunter@xxxxxxxxx>
> Cc: Ulf Hansson <ulf.hansson@xxxxxxxxxx>; linux-mmc <linux-
> mmc@xxxxxxxxxxxxxxx>; linux-block <linux-block@xxxxxxxxxxxxxxx>; linux-
> kernel <linux-kernel@xxxxxxxxxxxxxxx>; Bough Chen <haibo.chen@xxxxxxx>;
> Alex Lemberg <Alex.Lemberg@xxxxxxx>; Mateusz Nowak
> <mateusz.nowak@xxxxxxxxx>; Yuliy Izrailov <Yuliy.Izrailov@xxxxxxx>;
> Jaehoon Chung <jh80.chung@xxxxxxxxxxx>; Dong Aisheng
> <dongas86@xxxxxxxxx>; Das Asutosh <asutoshd@xxxxxxxxxxxxxx>; Zhangfei
> Gao <zhangfei.gao@xxxxxxxxx>; Sahitya Tummala
> <stummala@xxxxxxxxxxxxxx>; Harjani Ritesh <riteshh@xxxxxxxxxxxxxx>;
> Venu Byravarasu <vbyravarasu@xxxxxxxxxx>; Shawn Lin <shawn.lin@rock-
> chips.com>; Christoph Hellwig <hch@xxxxxx>
> Subject: Re: [PATCH V9 09/15] mmc: core: Add parameter use_blk_mq
> 
> On Fri, Sep 22, 2017 at 2:36 PM, Adrian Hunter <adrian.hunter@xxxxxxxxx>
> wrote:
> 
> > 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@xxxxxxxxx>
> 
> > +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 not take
> the intermediate step of having this as optional. Otherwise it never gets
> tested.
> 
> Set it to default y and after two kernel releases, if nothing happens, we simply
> delete the old block layer path.
> 
> > +#ifdef CONFIG_MMC_MQ_DEFAULT
> > +bool mmc_use_blk_mq = true;
> > +#else
> > +bool mmc_use_blk_mq = false;
> > +#endif
> > +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?


Module param can be changed in runtime

> 
> Maybe I'm the only developer stupid enough to just recompile and reboot the
> whole kernel, I guess this makes sense if you're testing on the same machine
> you're developing on (no cross-compilation and remote target) which I guess
> is what some Intel people are doing with their laptops.
> 
> Yours,
> Linus Walleij
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