Messages in this thread | | | Date | Tue, 22 Jul 2008 22:31:51 +0300 | From | Avi Kivity <> | Subject | Re: [patch 0/4] Port KVM-trace to tracepoints |
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Frank Ch. Eigler wrote: > Avi Kivity <avi@qumranet.com> writes: > > >> [...] >> kvm tracepoints are heavily tied into the implementation; and making >> them harder to write means we will have less information. In fact, I >> am contemplating moving in another direction (when looking at the >> pgprintk()s scattered around arch/x86/kvm/mmu.c: >> >> kvm_trace("pfentry", "page_fault entry addr %lx error code %x\n", >> cr2, error_code); >> >> Unlike printk()s, no actual formatting would occur during runtime. >> > > Have you considered using trace_mark() directly - eliminating the > KVM_TRACEN() middlemen? > >
Eliminating KVM_TRACEN -- yes. There are too many of them, they aren't type-aware, and they're in uppercase.
Using trace_mark() directly -- looking at it, seems to fit the requirements exactly. Should have looked at it earlier. Is there a way to get a list of all markers?
Perhaps the kvmtrace marker->relay integration should be made a marker feature, since there is nothing specific to kvm in it.
>> Instead, at initialization time all the strings would be parsed into >> a data structure that describes the data types, and the runtime >> would simply consult this structure and copy the arguments into >> trace records. User space would also be able to pull this structure >> and so recreate the formatted string. >> > > If one really wanted to, one could build such a mechanism on top of > marker-based callbacks. > >
One does want to.
>> - no need to have a formats file in userspace (which is tied to the >> kernel version) >> > > OTOH, you'd have the kernel collecting compact binary records > containing just the parameters, which are at least as tied to kernel > version. > >
Yes, but the userspace side would collect the format strings as well (just once) and could put them in the same file. The aggregation is portable across kernel versions.
-- I have a truly marvellous patch that fixes the bug which this signature is too narrow to contain.
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