linux-kernel - Re: [PATCH v2 16/33] x86/intel_rdt: Class of service and capacity bitmask management for CDP

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Date:   Thu, 8 Sep 2016 12:29:05 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Fenghua Yu <fenghua.yu@...el.com>
cc:     "H. Peter Anvin" <h.peter.anvin@...el.com>,
        Ingo Molnar <mingo@...e.hu>, Tony Luck <tony.luck@...el.com>,
        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 16/33] x86/intel_rdt: Class of service and capacity
 bitmask management for CDP

On Thu, 8 Sep 2016, Fenghua Yu wrote:

> Add support to manage CLOSid(CLass Of Service id) and capacity
> bitmask(cbm) for code data prioritization(CDP).

I manage to understand that.

> Closid management includes changes to allocating, freeing closid and
> closid_get and closid_put and changes to closid availability map during
> CDP set up. 

But this is just a random sequence of word, function names and a reference
to the availability map which is not touched at all in this patch.

> CDP has a separate cbm for code and data.

> +/*
> + * When cdp mode is enabled, refcnt is maintained in the dcache_cbm entry.

Sorry. I really cannot figure out what that means.

> + */
>  static inline void closid_get(u32 closid)
>  {
> -	struct clos_cbm_table *cct = &cctable[closid];
> +	struct clos_cbm_table *cct = &cctable[DCBM_TABLE_INDEX(closid)];
>  
>  	lockdep_assert_held(&rdtgroup_mutex);
>  
> @@ -139,7 +155,7 @@ static int closid_alloc(u32 *closid)
>  static inline void closid_free(u32 closid)
>  {
>  	clear_bit(closid, cconfig.closmap);
> -	cctable[closid].cbm = 0;
> +	cctable[DCBM_TABLE_INDEX(closid)].cbm = 0;
>  
>  	if (WARN_ON(!cconfig.closids_used))
>  		return;
> @@ -149,7 +165,7 @@ static inline void closid_free(u32 closid)
>  
>  static void closid_put(u32 closid)
>  {
> -	struct clos_cbm_table *cct = &cctable[closid];
> +	struct clos_cbm_table *cct = &cctable[DCBM_TABLE_INDEX(closid)];

So if CDP is disabled we look at table[closid] and if it's enabled we look
at table[closid << 1]. What is managing the interleaved entries in the
table?

Thanks,

	tglx