Messages in this thread | | | Date | Thu, 29 Mar 2012 12:12:47 -0700 | From | "H. Peter Anvin" <> | Subject | Re: [PATCH 4/6] trace: trace syscall in its handler not from ptrace handler |
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On 03/29/2012 12:02 PM, Vaibhav Nagarnaik wrote: > > Thanks for the feedback. I had missed this added latency due to this > patch when tracing is disabled. > > To fix that, instead of a TIF flag, I am using a flag in the > current->trace bitmap. I check that flag before jumping to the tracing > function. That reduces the latency from 83 ns/call to 74 ns/call. >
ANY increase to the fastpath is unacceptable, period.
Furthermore, as I have discussed with some people over the last few days, I think we should consider the whole syscall tracing interface set to be a mistake and deprecate it. There are much better ways to accomplish something that will work more reliable without all these thunks.
-hpa
-- H. Peter Anvin, Intel Open Source Technology Center I work for Intel. I don't speak on their behalf.
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