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s390/qdio: remove internal polling in non-thinint path

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For non-thinint devices in LPAR, qdio polls an idle Input Queue for a
little while to catch more work. But platform support for thinints has
been around practically _forever_ by now, so this micro-optimization is
seeing 0 actual use. Remove it to reduce the overall complexity of the
hot path.

In the meantime we also grew support for driver-level polling
(eg. NAPI in qeth), so it's quite questionable how useful this would
actually be on current kernels.

Signed-off-by: Julian Wiedmann <jwi@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
This commit is contained in:
Julian Wiedmann 2020-06-16 14:13:00 +02:00 committed by Heiko Carstens
parent 2bbf282a5e
commit a709423f7a
2 changed files with 2 additions and 27 deletions
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3
drivers/s390/cio/qdio.h
View File

@ -15,7 +15,6 @@
#define QDIO_BUSY_BIT_PATIENCE (100 << 12) /* 100 microseconds */
#define QDIO_BUSY_BIT_RETRY_DELAY 10 /* 10 milliseconds */
#define QDIO_BUSY_BIT_RETRIES 1000 /* = 10s retry time */
#define QDIO_INPUT_THRESHOLD (500 << 12) /* 500 microseconds */
enum qdio_irq_states {
QDIO_IRQ_STATE_INACTIVE,
@ -181,8 +180,6 @@ struct qdio_input_q {
/* Batch of SBALs that we processed while polling the queue: */
unsigned int batch_start;
unsigned int batch_count;
/* last time of noticing incoming data */
u64 timestamp;
};
struct qdio_output_q {

26
drivers/s390/cio/qdio_main.c
View File

@ -510,14 +510,7 @@ static int get_inbound_buffer_frontier(struct qdio_q *q, unsigned int start)
static int qdio_inbound_q_moved(struct qdio_q *q, unsigned int start)
{
int count;
count = get_inbound_buffer_frontier(q, start);
if (count && !is_thinint_irq(q->irq_ptr) && MACHINE_IS_LPAR)
q->u.in.timestamp = get_tod_clock();
return count;
return get_inbound_buffer_frontier(q, start);
}
static inline int qdio_inbound_q_done(struct qdio_q *q, unsigned int start)
@ -535,22 +528,7 @@ static inline int qdio_inbound_q_done(struct qdio_q *q, unsigned int start)
/* more work coming */
return 0;
if (is_thinint_irq(q->irq_ptr))
return 1;
/* don't poll under z/VM */
if (MACHINE_IS_VM)
return 1;
/*
* At this point we know, that inbound first_to_check
* has (probably) not moved (see qdio_inbound_processing).
*/
if (get_tod_clock_fast() > q->u.in.timestamp + QDIO_INPUT_THRESHOLD) {
DBF_DEV_EVENT(DBF_INFO, q->irq_ptr, "in done:%02x", start);
return 1;
} else
return 0;
return 1;
}
static inline void qdio_handle_aobs(struct qdio_q *q, int start, int count)