On 08.02.2018 08:41, Viktor Mihajlovski wrote: > On 07.02.2018 18:50, Luiz Capitulino wrote: >> The query-cpus command has an extremely serious side effect: >> it always interrupt all running vCPUs so that they can run >> ioctl calls. This can cause a huge performance degradation for >> some workloads. And most of the information retrieved by the >> ioctl calls are not even used by query-cpus. >> >> This commit introduces a replacement for query-cpus called >> query-cpus-fast, which has the following features: >> >> o Never interrupt vCPUs threads. query-cpus-fast only returns >> vCPU information maintained by QEMU itself, which should be >> sufficient for most management software needs >> >> o Make "halted" field optional: we only return it if the >> halted state is maintained by QEMU. But this also gives >> the option of dropping the field in the future (see below) >> >> o Drop irrelevant fields such as "current", "pc" and "arch" > I disagree that arch is irrelevant and would strongly suggest to keep > arch and arch-specific fields. At least in the case of s390 there's a > cpu_state field that can be obtained cheaply. I've posted a patch [1] to add s390-specific state info to the query-cpus output. This state *can* be obtained without kicking the CPU out of VM execution. With this info in the query-cpus-fast return data we can eventually get rid of halted and its ramifications. [...]
[1] https://lists.gnu.org/archive/html/qemu-devel/2018-02/msg02032.html -- Regards, Viktor Mihajlovski
