Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> writes:
> Quoting Mika Kuoppala (2017-10-31 15:27:34)
>> From: Mika Kuoppala <mika.kuoppala@xxxxxxxxx>
>>
>> As all our access to execlist ports are through head and tail
>> helpers, we can now move the head instead of memmoving the array.
>>
>> v2: use memset (Chris)
>>
>> Cc: Michał Winiarski <michal.winiarski@xxxxxxxxx>
>> Cc: Joonas Lahtinen <joonas.lahtinen@xxxxxxxxxxxxxxx>
>> Cc: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
>> Signed-off-by: Mika Kuoppala <mika.kuoppala@xxxxxxxxxxxxxxx>
>> ---
>> drivers/gpu/drm/i915/intel_ringbuffer.h | 10 +++++-----
>> 1 file changed, 5 insertions(+), 5 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.h b/drivers/gpu/drm/i915/intel_ringbuffer.h
>> index 387667fe50d3..011c4b8f1339 100644
>> --- a/drivers/gpu/drm/i915/intel_ringbuffer.h
>> +++ b/drivers/gpu/drm/i915/intel_ringbuffer.h
>> @@ -611,13 +611,13 @@ static inline struct execlist_port *
>> execlists_head_complete(struct intel_engine_execlists * const execlists,
>> struct execlist_port * const port)
>> {
>> - const unsigned int m = execlists->port_mask;
>> -
>> - GEM_BUG_ON(port_index(port, execlists) != 0);
>> + GEM_BUG_ON(port_index(port, execlists) != execlists->port_head);
>> + GEM_BUG_ON(!port_isset(port));
>> GEM_BUG_ON(!execlists_is_active(execlists, EXECLISTS_ACTIVE_USER));
>>
>> - memmove(port, port + 1, m * sizeof(struct execlist_port));
>> - memset(port + m, 0, sizeof(struct execlist_port));
>> + memset(port, 0, sizeof(*port));
>> +
>> + execlists->port_head = port_head_add(execlists, 1);
>
> Ok, I would have gone for
>
> port = port_next(port);
> execlists->port_head = port - execlists->port;
> return port;
>
> That to me looks more natural advance of port as we complete the
> requests, and matches the loop in the irq handler.
>
> Care to crunch the numbers and see which gcc favours?
gcc (Ubuntu 6.3.0-12ubuntu2) 6.3.0 20170406:
add/remove: 0/0 grow/shrink: 3/0 up/down: 219/0 (219)
function old new delta
execlists_submission_tasklet 2405 2525 +120
execlists_cancel_port_requests 315 376 +61
guc_submission_tasklet 1643 1681 +38
Total: Before=1168854, After=1169073, chg +0.02%
gcc (Ubuntu 7.2.0-8ubuntu3) 7.2.0:
add/remove: 0/0 grow/shrink: 3/0 up/down: 158/0 (158)
function old new delta
execlists_submission_tasklet 2383 2460 +77
execlists_cancel_port_requests 344 401 +57
guc_submission_tasklet 1684 1708 +24
Total: Before=1164662, After=1164820, chg +0.01%
where new:
execlists_head_complete(struct intel_engine_execlists * const execlists,
- struct execlist_port * const port)
+ struct execlist_port *port)
{
GEM_BUG_ON(port_index(port, execlists) != execlists->port_head);
GEM_BUG_ON(!port_isset(port));
@@ -677,9 +677,10 @@ execlists_head_complete(struct intel_engine_execlists * const execlists,
memset(port, 0, sizeof(*port));
- execlists->port_head = port_head_add(execlists, 1);
+ port = execlists_port_next(execlists, port);
+ execlists->port_head = port - execlists->port;
- return execlists_port_head(execlists);
+ return port;
-Mika
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