Messages in this thread | | | Date | Sat, 12 Apr 2008 23:05:44 +0200 (CEST) | From | Erik Bosman <> | Subject | Re: [PATCH 2/3] x86: Implement prctl PR_GET_TSC and PR_SET_TSC |
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On Sat, 12 Apr 2008, H. Peter Anvin wrote:
> Arjan van de Ven wrote: > > > > Hi, > > > > why did you make this a configuration option? In general it's not > > a good idea to make userspace visible ABI's (PR_* clearly is one of these) > > a CONFIG option unless there's some HUGE space saving going on. > > I don't see that here.... > > > > So can you explain your rationale for making this a config option? > >
The ABI itself is not a config option (see patch 1/3.) If the x86 implementation patch isn't applied, prctl() will return -EINVAL, just like most other PR_* options, which are only implemented on specific architectures, take (PR_GET/PR_SET_ENDIAN) as an example.
> > I also saw no mention about performance impact, which need to be > considered whenever *anything* is proposed to be inserted into a hot > path. It may be (heck, *should be*) that the performance impact isn't > measurable, but that needs to be positively established. >
This is why I made the implementation part configurable, although I don't think the overhead will be very high since it seems to me that the __switch_to_xtra function was designed explicitly to keep unusual options out of the hot path.
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