Re: [PATCH] Only process_die notifier in ia64_do_page_fault if KPROBES is configured.

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On Wed, 31 Aug 2005, Andi Kleen wrote:

> Also with the inline the test should be essentially a single test of 
> a global variable and jump. Hardly a big performance issue, no? 

There are multiple effects of this code.

- Additional cacheline in use in the page fault handler 
  increasing the cache foot print.

- There are registers in use for checking the global variable.

- The compilers will reserve registers for the code that is never 
  executed which may affect other elements of performance. From the 
  register perspective a function call may be better on ia64.

Certainly not a big effect (if we make sure the compiler knows that 
this test mostly fails and insure that the variable is in 
__mostly_read) but this is a frequently executed code path and the code
is there without purpose if CONFIG_KPROBES is off.

It wont get too bad unless lots of other people have similar ideas about 
fixing their race conditions using similar methods. But we will be setting 
a bad precedent if we allow this.
-
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]     [Gimp]     [Yosemite News]     [MIPS Linux]     [ARM Linux]     [Linux Security]     [Linux RAID]     [Video 4 Linux]     [Linux for the blind]
  Powered by Linux