Ingo Molnar <mi...@kernel.org> writes:
> * Peter Zijlstra <pet...@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.
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