RE: [PATCH V2 01/13] pm80xx : Increase request sg length.

Deepak.Ukey
2020-01-29T09:02:44Z

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On Mon, Jan 20, 2020 at 5:20 AM <Deepak.Ukey@microchip.com> wrote:
>
>
> EXTERNAL EMAIL: Do not click links or open attachments unless you know
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> On Fri, Jan 17, 2020 at 4:50 PM <Deepak.Ukey@microchip.com> wrote:
> >
> > On Fri, Jan 17, 2020 at 8:10 AM Deepak Ukey <deepak.ukey@microchip.com> wrote:
> > >
> > > From: Peter Chang <dpf@google.com>
> > >
> > > Increasing the per-request size maximum (max_sectors_kb) runs into
> > > the per-device dma scatter gather list limit (max_segments) for
> > > users of the io vector system calls (eg, readv and writev). This
> > > is because the kernel combines io vectors into dma segments when
> > > possible, but it doesn't work for our user because the vectors in
> > > the buffer cache get scrambled.
> > > This change bumps the advertised max scatter gather length to 528
> > > to cover 2M w/ x86's 4k pages and some extra for the user checksum.
> > > It trims the size of some of the tables we don't care about and
> > > exposes all of the command slots upstream to the scsi layer
> > >
> > > Signed-off-by: Peter Chang <dpf@google.com>
> > > Signed-off-by: Deepak Ukey <deepak.ukey@microchip.com>
> > > Signed-off-by: Viswas G <Viswas.G@microchip.com>
> > > Signed-off-by: Radha Ramachandran <radha@google.com>
> > > Reported-by: kbuild test robot <lkp@intel.com>
> > > ---
> > > drivers/scsi/pm8001/pm8001_defs.h | 5 +++--
> > > drivers/scsi/pm8001/pm8001_init.c | 2 +-
> > > 2 files changed, 4 insertions(+), 3 deletions(-)
> > >
> > > diff --git a/drivers/scsi/pm8001/pm8001_defs.h
> > > b/drivers/scsi/pm8001/pm8001_defs.h
> > > index 48e0624ecc68..1c7f15fd69ce 100644
> > > --- a/drivers/scsi/pm8001/pm8001_defs.h
> > > +++ b/drivers/scsi/pm8001/pm8001_defs.h
> > > @@ -75,7 +75,7 @@ enum port_type { };
> > >
> > > /* driver compile-time configuration */
> > > -#define PM8001_MAX_CCB 512 /* max ccbs supported */
> > > +#define PM8001_MAX_CCB 256 /* max ccbs supported */
> > Hi Deepack,
> >
> > Why do you reduce PM8001_MAX_CCB?
> > --- PM8001 driver has a memory limit in the machine.
> which limit, do you see allocation failure from kernel?
> -- I think it depends on machine's capability. For our machines,
> PM8001_MAX_CCB = 512 caused kernel installation failure. I saw it when
> I was debugging ncq feature Thanks
Ok, would be helpful to put this info to commit message.
> Thanks. I will add this in version 3 of the patchest.

Thanks