* Alan Cox <[email protected]> wrote:
> Ar Llu, 2006-09-18 am 17:22 +0200, ysgrifennodd Ingo Molnar:
> > yeah - but i think to make it easier for SystemTap to insert a
> > low-overhead probe there needs to be a 5-byte NOP inserted. There wont
> > be any function call or condition at that place. At most there will be
> > some minimal impact on the way gcc compiles the code in that function,
>
> And more L1 misses. It seems that this problem should be solved by
> jprobes and your int3 optimisation work.
Do you consider a single 5-byte NOP for a judiciously chosen 50 places
in the kernel unacceptable? Note that the argument has shifted from
static tracers to dynamic tracers: this _is_ about SystemTap: it adds
points to the kernel where we can _guarantee_ that a dynamic probe can
be inserted. In general there is no guarantee from gcc that any probe
can be inserted into a function (djprobes and int3 optimization
nonwithstanding) and this is a real practical problem for SystemTap.
Frank can attest to that.
Ingo
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
[Index of Archives]
[Kernel Newbies]
[Netfilter]
[Bugtraq]
[Photo]
[Stuff]
[Gimp]
[Yosemite News]
[MIPS Linux]
[ARM Linux]
[Linux Security]
[Linux RAID]
[Video 4 Linux]
[Linux for the blind]
[Linux Resources]
