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CONFIG_VIRT_CPU_ACCOUNTING_GEN under pseries does not provide stolen time accounting unless CONFIG_PARAVIRT_TIME_ACCOUNTING is enabled. Implement this using the VPA accumulated wait counters. Note this will not work on current KVM hosts because KVM does not implement the VPA dispatch counters (yet). It could be implemented with the dispatch trace log as it is for VIRT_CPU_ACCOUNTING_NATIVE, but that is not necessary for the more limited accounting provided by PARAVIRT_TIME_ACCOUNTING, and it is more expensive, complex, and has downsides like potential log wrap. From Shrikanth: [...] it was tested on Power10 [PowerVM] Shared LPAR. system has two LPAR. we will call first one LPAR1 and second one as LPAR2. Test was carried out in SMT=1. Similar observation was seen in SMT=8 as well. LPAR config header from each LPAR is below. LPAR1 is twice as big as LPAR2. Since Both are sharing the same underlying hardware, work stealing will happen when both the LPAR's are contending for the same resource. LPAR1: type=Shared mode=Uncapped smt=Off lcpu=40 cpus=40 ent=20.00 LPAR2: type=Shared mode=Uncapped smt=Off lcpu=20 cpus=40 ent=10.00 mpstat was used to check for the utilization. stress-ng has been used as the workload. Few cases are tested. when the both LPAR are idle there is no steal time. when LPAR1 starts running at 100% which consumes all of the physical resource, steal time starts to get accounted. With LPAR1 running at 100% and LPAR2 starts running, steal time starts increasing. This is as expected. When the LPAR2 Load is increased further, steal time increases further. Case 1: 0% LPAR1; 0% LPAR2 %usr %nice %sys %iowait %irq %soft %steal %guest %gnice %idle 0.00 0.00 0.05 0.00 0.00 0.00 0.00 0.00 0.00 99.95 Case 2: 100% LPAR1; 0% LPAR2 %usr %nice %sys %iowait %irq %soft %steal %guest %gnice %idle 97.68 0.00 0.00 0.00 0.00 0.00 2.32 0.00 0.00 0.00 Case 3: 100% LPAR1; 50% LPAR2 %usr %nice %sys %iowait %irq %soft %steal %guest %gnice %idle 86.34 0.00 0.10 0.00 0.00 0.03 13.54 0.00 0.00 0.00 Case 4: 100% LPAR1; 100% LPAR2 %usr %nice %sys %iowait %irq %soft %steal %guest %gnice %idle 78.54 0.00 0.07 0.00 0.00 0.02 21.36 0.00 0.00 0.00 Case 5: 50% LPAR1; 100% LPAR2 %usr %nice %sys %iowait %irq %soft %steal %guest %gnice %idle 49.37 0.00 0.00 0.00 0.00 0.00 1.17 0.00 0.00 49.47 Patch is accounting for the steal time and basic tests are holding good. Signed-off-by: Nicholas Piggin <npiggin@gmail.com> Tested-by: Shrikanth Hegde <sshegde@linux.ibm.com> [mpe: Add SPDX tag to new paravirt_api_clock.h] Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/20220902085316.2071519-3-npiggin@gmail.com |
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| README | ||
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.