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Re: [Xen-devel] [PATCH 1/2] add cpu_thread_id to struct cpuinfo_x86


  • To: Juergen Gross <jgross@xxxxxxxx>, Jan Beulich <JBeulich@xxxxxxxx>
  • From: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
  • Date: Mon, 3 Sep 2018 16:07:59 +0100
  • Autocrypt: addr=andrew.cooper3@xxxxxxxxxx; prefer-encrypt=mutual; keydata= xsFNBFLhNn8BEADVhE+Hb8i0GV6mihnnr/uiQQdPF8kUoFzCOPXkf7jQ5sLYeJa0cQi6Penp VtiFYznTairnVsN5J+ujSTIb+OlMSJUWV4opS7WVNnxHbFTPYZVQ3erv7NKc2iVizCRZ2Kxn srM1oPXWRic8BIAdYOKOloF2300SL/bIpeD+x7h3w9B/qez7nOin5NzkxgFoaUeIal12pXSR Q354FKFoy6Vh96gc4VRqte3jw8mPuJQpfws+Pb+swvSf/i1q1+1I4jsRQQh2m6OTADHIqg2E ofTYAEh7R5HfPx0EXoEDMdRjOeKn8+vvkAwhviWXTHlG3R1QkbE5M/oywnZ83udJmi+lxjJ5 YhQ5IzomvJ16H0Bq+TLyVLO/VRksp1VR9HxCzItLNCS8PdpYYz5TC204ViycobYU65WMpzWe LFAGn8jSS25XIpqv0Y9k87dLbctKKA14Ifw2kq5OIVu2FuX+3i446JOa2vpCI9GcjCzi3oHV e00bzYiHMIl0FICrNJU0Kjho8pdo0m2uxkn6SYEpogAy9pnatUlO+erL4LqFUO7GXSdBRbw5 gNt25XTLdSFuZtMxkY3tq8MFss5QnjhehCVPEpE6y9ZjI4XB8ad1G4oBHVGK5LMsvg22PfMJ ISWFSHoF/B5+lHkCKWkFxZ0gZn33ju5n6/FOdEx4B8cMJt+cWwARAQABzSlBbmRyZXcgQ29v cGVyIDxhbmRyZXcuY29vcGVyM0BjaXRyaXguY29tPsLBegQTAQgAJAIbAwULCQgHAwUVCgkI CwUWAgMBAAIeAQIXgAUCWKD95wIZAQAKCRBlw/kGpdefoHbdD/9AIoR3k6fKl+RFiFpyAhvO 59ttDFI7nIAnlYngev2XUR3acFElJATHSDO0ju+hqWqAb8kVijXLops0gOfqt3VPZq9cuHlh IMDquatGLzAadfFx2eQYIYT+FYuMoPZy/aTUazmJIDVxP7L383grjIkn+7tAv+qeDfE+txL4 SAm1UHNvmdfgL2/lcmL3xRh7sub3nJilM93RWX1Pe5LBSDXO45uzCGEdst6uSlzYR/MEr+5Z JQQ32JV64zwvf/aKaagSQSQMYNX9JFgfZ3TKWC1KJQbX5ssoX/5hNLqxMcZV3TN7kU8I3kjK mPec9+1nECOjjJSO/h4P0sBZyIUGfguwzhEeGf4sMCuSEM4xjCnwiBwftR17sr0spYcOpqET ZGcAmyYcNjy6CYadNCnfR40vhhWuCfNCBzWnUW0lFoo12wb0YnzoOLjvfD6OL3JjIUJNOmJy RCsJ5IA/Iz33RhSVRmROu+TztwuThClw63g7+hoyewv7BemKyuU6FTVhjjW+XUWmS/FzknSi dAG+insr0746cTPpSkGl3KAXeWDGJzve7/SBBfyznWCMGaf8E2P1oOdIZRxHgWj0zNr1+ooF /PzgLPiCI4OMUttTlEKChgbUTQ+5o0P080JojqfXwbPAyumbaYcQNiH1/xYbJdOFSiBv9rpt TQTBLzDKXok86M7BTQRS4TZ/ARAAkgqudHsp+hd82UVkvgnlqZjzz2vyrYfz7bkPtXaGb9H4 Rfo7mQsEQavEBdWWjbga6eMnDqtu+FC+qeTGYebToxEyp2lKDSoAsvt8w82tIlP/EbmRbDVn 7bhjBlfRcFjVYw8uVDPptT0TV47vpoCVkTwcyb6OltJrvg/QzV9f07DJswuda1JH3/qvYu0p vjPnYvCq4NsqY2XSdAJ02HrdYPFtNyPEntu1n1KK+gJrstjtw7KsZ4ygXYrsm/oCBiVW/OgU g/XIlGErkrxe4vQvJyVwg6YH653YTX5hLLUEL1NS4TCo47RP+wi6y+TnuAL36UtK/uFyEuPy wwrDVcC4cIFhYSfsO0BumEI65yu7a8aHbGfq2lW251UcoU48Z27ZUUZd2Dr6O/n8poQHbaTd 6bJJSjzGGHZVbRP9UQ3lkmkmc0+XCHmj5WhwNNYjgbbmML7y0fsJT5RgvefAIFfHBg7fTY/i kBEimoUsTEQz+N4hbKwo1hULfVxDJStE4sbPhjbsPCrlXf6W9CxSyQ0qmZ2bXsLQYRj2xqd1 bpA+1o1j2N4/au1R/uSiUFjewJdT/LX1EklKDcQwpk06Af/N7VZtSfEJeRV04unbsKVXWZAk uAJyDDKN99ziC0Wz5kcPyVD1HNf8bgaqGDzrv3TfYjwqayRFcMf7xJaL9xXedMcAEQEAAcLB XwQYAQgACQUCUuE2fwIbDAAKCRBlw/kGpdefoG4XEACD1Qf/er8EA7g23HMxYWd3FXHThrVQ HgiGdk5Yh632vjOm9L4sd/GCEACVQKjsu98e8o3ysitFlznEns5EAAXEbITrgKWXDDUWGYxd pnjj2u+GkVdsOAGk0kxczX6s+VRBhpbBI2PWnOsRJgU2n10PZ3mZD4Xu9kU2IXYmuW+e5KCA vTArRUdCrAtIa1k01sPipPPw6dfxx2e5asy21YOytzxuWFfJTGnVxZZSCyLUO83sh6OZhJkk b9rxL9wPmpN/t2IPaEKoAc0FTQZS36wAMOXkBh24PQ9gaLJvfPKpNzGD8XWR5HHF0NLIJhgg 4ZlEXQ2fVp3XrtocHqhu4UZR4koCijgB8sB7Tb0GCpwK+C4UePdFLfhKyRdSXuvY3AHJd4CP 4JzW0Bzq/WXY3XMOzUTYApGQpnUpdOmuQSfpV9MQO+/jo7r6yPbxT7CwRS5dcQPzUiuHLK9i nvjREdh84qycnx0/6dDroYhp0DFv4udxuAvt1h4wGwTPRQZerSm4xaYegEFusyhbZrI0U9tJ B8WrhBLXDiYlyJT6zOV2yZFuW47VrLsjYnHwn27hmxTC/7tvG3euCklmkn9Sl9IAKFu29RSo d5bD8kMSCYsTqtTfT6W4A3qHGvIDta3ptLYpIAOD2sY3GYq2nf3Bbzx81wZK14JdDDHUX2Rs 6+ahAA==
  • Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>, Wei Liu <wei.liu2@xxxxxxxxxx>, George Dunlap <George.Dunlap@xxxxxxxxxxxxx>, Tim Deegan <tim@xxxxxxx>, Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>, xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>
  • Delivery-date: Mon, 03 Sep 2018 15:08:06 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
  • Openpgp: preference=signencrypt

On 03/09/18 15:52, Juergen Gross wrote:
> On 03/09/18 16:47, Jan Beulich wrote:
>>>>> On 03.09.18 at 15:53, <jgross@xxxxxxxx> wrote:
>>> On 03/09/18 15:46, Jan Beulich wrote:
>>>>>>> On 31.08.18 at 18:22, <jgross@xxxxxxxx> wrote:
>>>>> Add the thread-id to the cpu config data and an accessor macro
>>>>> cpu_to_thread().
>>>>>
>>>>> Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
>>>>> ---
>>>>>  xen/arch/x86/cpu/common.c       |  1 +
>>>>>  xen/arch/x86/smpboot.c          | 10 ++++++++++
>>>>>  xen/include/asm-arm/processor.h |  1 +
>>>>>  xen/include/asm-x86/processor.h |  2 ++
>>>>>  xen/include/public/sysctl.h     |  1 +
>>>>>  5 files changed, 15 insertions(+)
>>>>>
>>>>> diff --git a/xen/arch/x86/cpu/common.c b/xen/arch/x86/cpu/common.c
>>>>> index 057859ab14..f626a6a510 100644
>>>>> --- a/xen/arch/x86/cpu/common.c
>>>>> +++ b/xen/arch/x86/cpu/common.c
>>>>> @@ -434,6 +434,7 @@ void identify_cpu(struct cpuinfo_x86 *c)
>>>>>   c->phys_proc_id = XEN_INVALID_SOCKET_ID;
>>>>>   c->cpu_core_id = XEN_INVALID_CORE_ID;
>>>>>   c->compute_unit_id = INVALID_CUID;
>>>>> + c->cpu_thread_id = XEN_INVALID_THREAD_ID;
>>>>>   memset(&c->x86_capability, 0, sizeof c->x86_capability);
>>>>>  
>>>>>   generic_identify(c);
>>>>> diff --git a/xen/arch/x86/smpboot.c b/xen/arch/x86/smpboot.c
>>>>> index 7e76cc3d68..2c6a40c543 100644
>>>>> --- a/xen/arch/x86/smpboot.c
>>>>> +++ b/xen/arch/x86/smpboot.c
>>>>> @@ -247,6 +247,8 @@ static void set_cpu_sibling_map(unsigned int cpu)
>>>>>      cpumask_set_cpu(cpu, per_cpu(cpu_core_mask, cpu));
>>>>>      cpumask_set_cpu(cpu, per_cpu(cpu_sibling_mask, cpu));
>>>>>  
>>>>> +    c[cpu].cpu_thread_id = 0;
>>>>> +
>>>>>      if ( c[cpu].x86_num_siblings > 1 )
>>>>>      {
>>>>>          for_each_cpu ( i, &cpu_sibling_setup_map )
>>>>> @@ -270,6 +272,14 @@ static void set_cpu_sibling_map(unsigned int cpu)
>>>>>                         "CPU%u: unclear relationship with CPU%u\n",
>>>>>                         cpu, i);
>>>>>          }
>>>>> +
>>>>> +        for_each_cpu ( i, per_cpu(cpu_sibling_mask, cpu) )
>>>>> +        {
>>>>> +            if ( cpu == i )
>>>>> +                break;
>>>>> +            c[cpu].cpu_thread_id++;
>>>> No. This wants doing alongside setting of the other similar fields,
>>>> i.e. in (at least) detect_extended_topology() and detect_ht(). It
>>>> is the hardware which tells us what the thread ID is.
>>> I wasn't able to find the related information for AMD cpus. In case it
>>> is in the specs it is hidden very well.
>> What was used for compute units in Fam16 and earlier is used for
>> hyperthreads in Fam17 (and going forward, from what iirc Brian
>> has said).
> And what about hyperthreads in Fam16 and earlier? Or are "compute units"
> just another name for the threads and I can rename that field?

Fam 15/16 "Compute Units" are complicated.

The have a shared L1 I$, fetch and branch prediction, separate integer
pipelines, but a shared FPU pipeline.

Half of the pipeline looks very much like threads, and half looks like
separate cores.

~Andrew

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