lkml.org 
[lkml]   [2015]   [Apr]   [13]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
SubjectRe: [PATCH v5 10/10] module: Rework module_addr_{min,max}
Date
Ingo Molnar <mingo@kernel.org> writes:
> * Peter Zijlstra <peterz@infradead.org> wrote:
>
>> __module_address() does an initial bound check before doing the
>> {list/tree} iteration to find the actual module. The bound variables
>> are nowhere near the mod_tree cacheline, in fact they're nowhere
>> near one another.
>>
>> module_addr_min lives in .data while module_addr_max lives in .bss
>> (smarty pants GCC thinks the explicit 0 assignment is a mistake).
>>
>> Rectify this by moving the two variables into a structure together
>> with the latch_tree_root to guarantee they all share the same
>> cacheline and avoid hitting two extra cachelines for the lookup.
>>
>> While reworking the bounds code, move the bound update from
>> allocation to insertion time, this avoids updating the bounds for a
>> few error paths.
>
>> +static struct mod_tree_root {
>> + struct latch_tree_root root;
>> + unsigned long addr_min;
>> + unsigned long addr_max;
>> +} mod_tree __cacheline_aligned = {
>> + .addr_min = -1UL,
>> +};
>> +
>> +#define module_addr_min mod_tree.addr_min
>> +#define module_addr_max mod_tree.addr_max

Nice catch.

Does the min/max comparison still win us anything? (I'm guessing yes...)

In general, I'm happy with this series. Assume you want another
go-round for Ingo's tweaks, then I'll take them for 4.2.

Thanks,
Rusty.


\
 
 \ /
  Last update: 2015-04-14 05:41    [W:0.611 / U:1.988 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site