On 1/16/2025 9:48 PM, Xin Li wrote:
On 1/16/2025 5:03 AM, Ethan Zhao wrote:
On 1/16/2025 3:27 PM, Xin Li wrote:
On 1/15/2025 10:51 PM, Ethan Zhao wrote:
External interrupts (EVENT_TYPE_EXTINT) and system calls
(EVENT_TYPE_OTHER)
occur more frequently than other events in a typical system.
Prioritizing
these events saves CPU cycles and optimizes the efficiency of
performance-
critical paths.
We deliberately hold off sending performance improvement patches at
this
point, but first of all please read:
https://lore.kernel.org/lkml/87fs766o3t.ffs@tglx/
Do you mean Thomas'point "Premature optimization is the enemy of
correctness.
don't do it" ? Yep, I agree with it.
Yes.
Compared to the asm code generated by the compiler with fewer than 20
cmp
instructions, placing a event handler jump table indexed by event-
typethere is a negative optimization. That is not deliberately 'hold
off', correctness goes first, definitely right.
hpa suggested to introduce "switch_likely" for this kind of optimization
on a switch statement, which is also easier to read. I measured it with
a user space focus test, it does improve performance a lot. But
obviously there are still a lot of work to do.
Find a way to instruct compiler to pick the right hot branch meanwhile make folks
reading happy... yup, a lot of work.
Thanks,
Ethan
Thanks!
Xin
