linux-kernel - Re: [PATCH v2 07/33] x86/intel_rdt: Add support for Cache Allocation detection

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Date:   Tue, 13 Sep 2016 15:52:18 -0700
From:   "Luck, Tony" <tony.luck@...el.com>
To:     Dave Hansen <dave.hansen@...el.com>
Cc:     Fenghua Yu <fenghua.yu@...el.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        "H. Peter Anvin" <h.peter.anvin@...el.com>,
        Ingo Molnar <mingo@...e.hu>,
        Peter Zijlstra <peterz@...radead.org>,
        Tejun Heo <tj@...nel.org>, Borislav Petkov <bp@...e.de>,
        Stephane Eranian <eranian@...gle.com>,
        Marcelo Tosatti <mtosatti@...hat.com>,
        David Carrillo-Cisneros <davidcc@...gle.com>,
        Shaohua Li <shli@...com>,
        Ravi V Shankar <ravi.v.shankar@...el.com>,
        Vikas Shivappa <vikas.shivappa@...ux.intel.com>,
        Sai Prakhya <sai.praneeth.prakhya@...el.com>,
        linux-kernel <linux-kernel@...r.kernel.org>, x86 <x86@...nel.org>
Subject: Re: [PATCH v2 07/33] x86/intel_rdt: Add support for Cache Allocation
 detection

On Tue, Sep 13, 2016 at 03:40:18PM -0700, Dave Hansen wrote:
> Are you sure you don't want to add RDT to disabled-features.h?  You have
> a config option for it, so it seems like you should also be able to
> optimize some of these checks away when the config option is off.

Makefile looks like this:

obj-$(CONFIG_INTEL_RDT)        += intel_rdt.o intel_rdt_rdtgroup.o intel_rdt_schemata.o

which seems to skip compiling all our code when the CONFIG
option is off.

Our hooks to generic code look like:

+#ifdef CONFIG_INTEL_RDT
+extern void rdtgroup_fork(struct task_struct *child);
+extern void rdtgroup_exit(struct task_struct *tsk);
+#else
+static inline void rdtgroup_fork(struct task_struct *child) {}
+static inline void rdtgroup_exit(struct task_struct *tsk) {}
+#endif /* CONFIG_INTEL_RDT */


Does this disabled-features.h thing do something more?

-Tony