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From: Randy Dunlap <rdunlap@infradead.org>
To: Reinette Chatre <reinette.chatre@intel.com>,
	tglx@linutronix.de, fenghua.yu@intel.com, tony.luck@intel.com
Cc: gavin.hindman@intel.com, vikas.shivappa@linux.intel.com,
	dave.hansen@intel.com, mingo@redhat.com, hpa@zytor.com,
	x86@kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH V2 01/22] x86/intel_rdt: Documentation for Cache Pseudo-Locking
Date: Mon, 19 Feb 2018 13:27:33 -0800	[thread overview]
Message-ID: <ae8252f6-83b4-d8d6-8eaf-ecbae78339aa@infradead.org> (raw)
In-Reply-To: <9416db57e47e2040a7108ba269f5432d0c91f1f7.1518443616.git.reinette.chatre@intel.com>

On 02/13/18 07:46, Reinette Chatre wrote:
> Add description of Cache Pseudo-Locking feature, its interface,
> as well as an example of its usage.
> 
> Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
> ---
>  Documentation/x86/intel_rdt_ui.txt | 229 ++++++++++++++++++++++++++++++++++++-
>  1 file changed, 228 insertions(+), 1 deletion(-)
> 
> diff --git a/Documentation/x86/intel_rdt_ui.txt b/Documentation/x86/intel_rdt_ui.txt
> index 756fd76b78a6..bb3d6fe0a3e4 100644
> --- a/Documentation/x86/intel_rdt_ui.txt
> +++ b/Documentation/x86/intel_rdt_ui.txt

> @@ -329,6 +332,149 @@ L3CODE:0=fffff;1=fffff;2=fffff;3=fffff
>  L3DATA:0=fffff;1=fffff;2=3c0;3=fffff
>  L3CODE:0=fffff;1=fffff;2=fffff;3=fffff
>  
> +Cache Pseudo-Locking
> +--------------------
> +CAT enables a user to specify the amount of cache space into which an

                                                     space that an

> +application can fill. Cache pseudo-locking builds on the fact that a
> +CPU can still read and write data pre-allocated outside its current
> +allocated area on a cache hit. With cache pseudo-locking, data can be
> +preloaded into a reserved portion of cache that no application can
> +fill, and from that point on will only serve cache hits. The cache
> +pseudo-locked memory is made accessible to user space where an
> +application can map it into its virtual address space and thus have
> +a region of memory with reduced average read latency.
> +
> +Cache pseudo-locking increases the probability that data will remain
> +in the cache via carefully configuring the CAT feature and controlling
> +application behavior. There is no guarantee that data is placed in
> +cache. Instructions like INVD, WBINVD, CLFLUSH, etc. can still evict
> +“locked” data from cache. Power management C-states may shrink or
> +power off cache. It is thus recommended to limit the processor maximum
> +C-state, for example, by setting the processor.max_cstate kernel parameter.
> +
> +It is required that an application using a pseudo-locked region runs
> +with affinity to the cores (or a subset of the cores) associated
> +with the cache on which the pseudo-locked region resides. This is
> +enforced by the implementation.
> +
> +Pseudo-locking is accomplished in two stages:
> +1) During the first stage the system administrator allocates a portion
> +   of cache that should be dedicated to pseudo-locking. At this time an
> +   equivalent portion of memory is allocated, loaded into allocated
> +   cache portion, and exposed as a character device.
> +2) During the second stage a user-space application maps (mmap()) the
> +   pseudo-locked memory into its address space.
> +
> +Cache Pseudo-Locking Interface
> +------------------------------
> +Platforms supporting cache pseudo-locking will expose a new
> +"/sys/fs/restrl/pseudo_lock" directory after successful mount of the
> +resctrl filesystem. Initially this directory will contain a single file,
> +"avail" that contains the schemata, one line per resource, of cache region
> +available for pseudo-locking.

uh, sysfs is supposed to be one value per file.

> +A pseudo-locked region is created by creating a new directory within
> +/sys/fs/resctrl/pseudo_lock. On success two new files will appear in
> +the directory:
> +
> +"schemata":
> +	Shows the schemata representing the pseudo-locked cache region.
> +	User writes schemata of requested locked area to file.

	use complete sentences, please. E.g.:

	The user writes the schemata of the requested locked area to the file.

> +	Only one id of single resource accepted - can only lock from

	            of a single resource is accepted -

> +	single cache instance. Writing of schemata to this file will
> +	return success on successful pseudo-locked region setup.
> +"size":
> +	After successful pseudo-locked region setup this read-only file
> +	will contain the size in bytes of pseudo-locked region.


-- 
~Randy

  parent reply	other threads:[~2018-02-19 21:27 UTC|newest]

Thread overview: 65+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-02-13 15:46 [RFC PATCH V2 00/22] Intel(R) Resource Director Technology Cache Pseudo-Locking enabling Reinette Chatre
2018-02-13 15:46 ` [RFC PATCH V2 01/22] x86/intel_rdt: Documentation for Cache Pseudo-Locking Reinette Chatre
2018-02-19 20:35   ` Thomas Gleixner
2018-02-19 22:15     ` Reinette Chatre
2018-02-19 22:19       ` Thomas Gleixner
2018-02-19 22:24         ` Reinette Chatre
2018-02-19 21:27   ` Randy Dunlap [this message]
2018-02-19 22:21     ` Reinette Chatre
2018-02-13 15:46 ` [RFC PATCH V2 02/22] x86/intel_rdt: Make useful functions available internally Reinette Chatre
2018-02-13 15:46 ` [RFC PATCH V2 03/22] x86/intel_rdt: Introduce hooks to create pseudo-locking files Reinette Chatre
2018-02-13 15:46 ` [RFC PATCH V2 04/22] x86/intel_rdt: Introduce test to determine if closid is in use Reinette Chatre
2018-02-13 15:46 ` [RFC PATCH V2 05/22] x86/intel_rdt: Print more accurate pseudo-locking availability Reinette Chatre
2018-02-13 15:46 ` [RFC PATCH V2 06/22] x86/intel_rdt: Create pseudo-locked regions Reinette Chatre
2018-02-19 20:57   ` Thomas Gleixner
2018-02-19 23:02     ` Reinette Chatre
2018-02-19 23:16       ` Thomas Gleixner
2018-02-20  3:21         ` Reinette Chatre
2018-02-13 15:46 ` [RFC PATCH V2 07/22] x86/intel_rdt: Connect pseudo-locking directory to operations Reinette Chatre
2018-02-13 15:46 ` [RFC PATCH V2 08/22] x86/intel_rdt: Introduce pseudo-locking resctrl files Reinette Chatre
2018-02-19 21:01   ` Thomas Gleixner
2018-02-13 15:46 ` [RFC PATCH V2 09/22] x86/intel_rdt: Discover supported platforms via prefetch disable bits Reinette Chatre
2018-02-13 15:46 ` [RFC PATCH V2 10/22] x86/intel_rdt: Disable pseudo-locking if CDP enabled Reinette Chatre
2018-02-13 15:46 ` [RFC PATCH V2 11/22] x86/intel_rdt: Associate pseudo-locked regions with its domain Reinette Chatre
2018-02-19 21:19   ` Thomas Gleixner
2018-02-19 23:00     ` Reinette Chatre
2018-02-19 23:19       ` Thomas Gleixner
2018-02-20  3:17         ` Reinette Chatre
2018-02-20 10:00           ` Thomas Gleixner
2018-02-20 16:02             ` Reinette Chatre
2018-02-20 17:18               ` Thomas Gleixner
2018-02-13 15:46 ` [RFC PATCH V2 12/22] x86/intel_rdt: Support CBM checking from value and character buffer Reinette Chatre
2018-02-13 15:46 ` [RFC PATCH V2 13/22] x86/intel_rdt: Support schemata write - pseudo-locking core Reinette Chatre
2018-02-20 17:15   ` Thomas Gleixner
2018-02-20 18:47     ` Reinette Chatre
2018-02-20 23:21       ` Thomas Gleixner
2018-02-21  1:58         ` Mike Kravetz
2018-02-21  6:10           ` Reinette Chatre
2018-02-21  8:34           ` Thomas Gleixner
2018-02-21  5:58         ` Reinette Chatre
2018-02-27  0:34     ` Reinette Chatre
2018-02-27 10:36       ` Thomas Gleixner
2018-02-27 15:38         ` Thomas Gleixner
2018-02-27 19:52         ` Reinette Chatre
2018-02-27 21:33           ` Reinette Chatre
2018-02-28 18:39           ` Thomas Gleixner
2018-02-28 19:17             ` Reinette Chatre
2018-02-28 19:40               ` Thomas Gleixner
2018-02-27 21:01     ` Reinette Chatre
2018-02-28 17:57       ` Thomas Gleixner
2018-02-28 17:59         ` Thomas Gleixner
2018-02-28 18:34           ` Reinette Chatre
2018-02-28 18:42             ` Thomas Gleixner
2018-02-13 15:46 ` [RFC PATCH V2 14/22] x86/intel_rdt: Enable testing for pseudo-locked region Reinette Chatre
2018-02-13 15:46 ` [RFC PATCH V2 15/22] x86/intel_rdt: Prevent new allocations from pseudo-locked regions Reinette Chatre
2018-02-13 15:47 ` [RFC PATCH V2 16/22] x86/intel_rdt: Create debugfs files for pseudo-locking testing Reinette Chatre
2018-02-13 15:47 ` [RFC PATCH V2 17/22] x86/intel_rdt: Create character device exposing pseudo-locked region Reinette Chatre
2018-02-13 15:47 ` [RFC PATCH V2 18/22] x86/intel_rdt: More precise L2 hit/miss measurements Reinette Chatre
2018-02-13 15:47 ` [RFC PATCH V2 19/22] x86/intel_rdt: Support L3 cache performance event of Broadwell Reinette Chatre
2018-02-13 15:47 ` [RFC PATCH V2 20/22] x86/intel_rdt: Limit C-states dynamically when pseudo-locking active Reinette Chatre
2018-02-13 15:47 ` [RFC PATCH V2 21/22] mm/hugetlb: Enable large allocations through gigantic page API Reinette Chatre
2018-02-13 15:47 ` [RFC PATCH V2 22/22] x86/intel_rdt: Support contiguous memory of all sizes Reinette Chatre
2018-02-14 18:12 ` [RFC PATCH V2 00/22] Intel(R) Resource Director Technology Cache Pseudo-Locking enabling Mike Kravetz
2018-02-14 18:31   ` Reinette Chatre
2018-02-15 20:39     ` Reinette Chatre
2018-02-15 21:10       ` Mike Kravetz

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