RE: [PATCH v3 4/6] x86/MCE: Make number of MCA banks per_cpu

[Ghannam, Yazen]

> -----Original Message-----
> From: linux-edac-owner@xxxxxxxxxxxxxxx <linux-edac-owner@xxxxxxxxxxxxxxx> On Behalf Of Borislav Petkov
> Sent: Tuesday, May 21, 2019 6:09 PM
> To: Luck, Tony <tony.luck@xxxxxxxxx>
> Cc: Ghannam, Yazen <Yazen.Ghannam@xxxxxxx>; linux-edac@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; x86@xxxxxxxxxx
> Subject: Re: [PATCH v3 4/6] x86/MCE: Make number of MCA banks per_cpu
> 
> 
> On Tue, May 21, 2019 at 01:42:40PM -0700, Luck, Tony wrote:
> > On Tue, May 21, 2019 at 10:29:02PM +0200, Borislav Petkov wrote:
> > >
> > > Can we do instead:
> > >
> > > -static DEFINE_PER_CPU_READ_MOSTLY(struct mce_bank *, mce_banks_array);
> > > +static DEFINE_PER_CPU_READ_MOSTLY(struct mce_bank, mce_banks_array[MAX_NR_BANKS]);
> > >
> > > which should be something like 9*32 = 288 bytes per CPU.
> > >
> >
> > Where did you get the "9" from?  struct mce_bank looks to
> > be over 50 bytes.
> 
> Patch 2/6 changes that:
> 
>  struct mce_bank {
>         u64                     ctl;                    /* subevents to enable */
>         bool                    init;                   /* initialise bank? */
> +};
> +static DEFINE_PER_CPU_READ_MOSTLY(struct mce_bank *, mce_banks_percpu);
> +
> +#define ATTR_LEN               16
> +/* One object for each MCE bank, shared by all CPUs */
> +struct mce_bank_dev {
>         struct device_attribute attr;                   /* device attribute */
>         char                    attrname[ATTR_LEN];     /* attribute name */
> +       u8                      bank;                   /* bank number */
>  };
> +static struct mce_bank_dev mce_bank_devs[MAX_NR_BANKS];
> 
> > Still only 1.5K per cpu though.
> 
> Yah, I think that using static per-CPU memory should be better than
> GFP_ATOMIC.
> 

Okay, makes sense. I'll send a patch soon.

Thanks,
Yazen