Re: [PATCH] speed up on find_first_bit for i386 (let compiler do the work)

Steven Rostedt wrote:
> In the thread "[RFC][PATCH] Make MAX_RT_PRIO and MAX_USER_RT_PRIO
> configurable" I discovered that a C version of find_first_bit is faster
> than the asm version

There are probably other cases of this in asm-i386/bitopts.h.  For instance
I think the "btl" instruction is pretty slow on modern CPUs so
constant_test_bit() will probably outperform variable_test_bit() even if
you feed it a non-constant "nr".  I'd be happy to be proven wrong, though :-)

When testing these optimizations you should also probably check the resulting
vmlinux size.

-Mitch
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• References:
  • [RFC][PATCH] Make MAX_RT_PRIO and MAX_USER_RT_PRIO configurable
    • From: Steven Rostedt <[email protected]>
  • Re: [RFC][PATCH] Make MAX_RT_PRIO and MAX_USER_RT_PRIO configurable
    • From: Daniel Walker <[email protected]>
  • Re: [RFC][PATCH] Make MAX_RT_PRIO and MAX_USER_RT_PRIO configurable
    • From: Steven Rostedt <[email protected]>
  • Re: [RFC][PATCH] Make MAX_RT_PRIO and MAX_USER_RT_PRIO configurable
    • From: Steven Rostedt <[email protected]>
  • Re: [RFC][PATCH] Make MAX_RT_PRIO and MAX_USER_RT_PRIO configurable
    • From: Steven Rostedt <[email protected]>
  • Re: [RFC][PATCH] Make MAX_RT_PRIO and MAX_USER_RT_PRIO configurable
    • From: Steven Rostedt <[email protected]>
  • Re: [RFC][PATCH] Make MAX_RT_PRIO and MAX_USER_RT_PRIO configurable
    • From: Nick Piggin <[email protected]>
  • [PATCH] speed up on find_first_bit for i386 (let compiler do the work)
    • From: Steven Rostedt <[email protected]>

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