From: Reinette Chatre <reinette.chatre@intel.com>
To: Randy Dunlap <rdunlap@infradead.org>,
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 14:21:43 -0800 [thread overview]
Message-ID: <a5ebbd0b-3e7c-44a7-391e-4856ae3257cd@intel.com> (raw)
In-Reply-To: <ae8252f6-83b4-d8d6-8eaf-ecbae78339aa@infradead.org>
Hi Randy,
On 2/19/2018 1:27 PM, Randy Dunlap wrote:
> 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
Will fix.
>
>> +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.
This builds on how the schemata file currently works.
>> +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 -
>
Will fix both.
>> + 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.
>
>
Thank you very much for taking a look!
Reinette
next prev parent reply other threads:[~2018-02-19 22:21 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
2018-02-19 22:21 ` Reinette Chatre [this message]
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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