Re: [PATCH 7/7] drm/i915: Trim unused workaround list entries

[Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>]

On 30/11/2018 21:58, Chris Wilson wrote:
> Quoting Tvrtko Ursulin (2018-11-30 17:44:12)
>> From: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
>>
>> The new workaround list allocator grows the list in chunks so will end up
>> with some unused space. Trim it when the initialization phase is done to
>> free up a tiny bit of slab.
>>
>> v2:
>>   * Simplify with kmemdup. (Chris Wilson)
>>
>> Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
>> ---
>>   drivers/gpu/drm/i915/intel_workarounds.c | 13 +++++++++++++
>>   1 file changed, 13 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/i915/intel_workarounds.c b/drivers/gpu/drm/i915/intel_workarounds.c
>> index 3e6b388ea022..9d876d554e57 100644
>> --- a/drivers/gpu/drm/i915/intel_workarounds.c
>> +++ b/drivers/gpu/drm/i915/intel_workarounds.c
>> @@ -55,6 +55,19 @@ static void wa_init_start(struct i915_wa_list *wal, const char *name)
>>   
>>   static void wa_init_finish(struct i915_wa_list *wal)
>>   {
>> +       /* Trim unused entries. */
>> +       if (wal->count < wal->__size) {
>> +               struct i915_wa *list = kmemdup(wal->list,
>> +                                              wal->count * sizeof(*list),
>> +                                              GFP_KERNEL);
>> +
>> +               if (list) {
>> +                       kfree(wal->list);
>> +                       wal->list = list;
>> +                       wal->__size = wal->count;
> 
> Hmm. We could kill __size entirely if you reallocated on
> is_power_of_two(wal->count).

You mean allocate to next power of two is is_power_of_two(wal->count) ? 
In that case I could also allocate to next ALIGN(wal->count, CHUNK_SIZE) 
if IS_ALIGNED which looks more appropriate for this particular use case.

Can't decide whether it is worth it though. Why not..

Regards,

Tvrtko

> Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
> -Chris
> 
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