Messages in this thread | | | From | Stanislaw Gruszka <> | Subject | [PATCH -tip 0/4] do not make cputime scaling in kernel | Date | Thu, 4 Apr 2013 11:10:31 +0200 |
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This patch series removes cputime scaling from kernel. It can be easily done in user space using floating point if we provide sum_exec_runtime, what patches 2/4 and 3/4 do. I have procps patch which utilize that:
http://people.redhat.com/sgruszka/procps-use-sum_exec_runtime.patch
I will post it, if this patch set will be queued.
Change affect also getrusage() and times() syscals, but I don't think kernel give guarantees about utime/stime precision, in a matter of fact before commit b27f03d4bdc145a09fb7b0c0e004b29f1ee555fa, we do not perform any scaling and we provided raw cputime values to user space.
Providing sum_exec_runtime via proc is done against malware that utilize lot of cpu time but hide itself from top program.
This affect kernels not compiled with CONFIG_VIRT_CPU_ACCOUNTING_{GEN,NATIVE}, if user choose to compile kernel with some of those options, he/she will have more precise cputime accounting, what is documented in Kconfig.
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