linux-kernel - Re: [PATCH v3 4/6] x86/MCE: Make number of MCA banks per

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Date:   Wed, 22 May 2019 01:09:27 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     "Luck, Tony" <tony.luck@...el.com>
Cc:     "Ghannam, Yazen" <Yazen.Ghannam@....com>,
        "linux-edac@...r.kernel.org" <linux-edac@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "x86@...nel.org" <x86@...nel.org>
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.

-- 
Regards/Gruss,
    Boris.

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