From: Julian Wiedmann <jwi@linux.ibm.com>
Date: Tue, 16 Jun 2020 14:13:00 +0200
Subject: s390/qdio: remove internal polling in non-thinint path
Git-commit: a709423f7a3a452e5fa7442425817c1bdccd7926
Patch-mainline: v5.9-rc1
References: jsc#SLE-13690
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>
Acked-by: Petr Tesarik <ptesarik@suse.com>
---
drivers/s390/cio/qdio.h | 3 ---
drivers/s390/cio/qdio_main.c | 26 ++------------------------
2 files changed, 2 insertions(+), 27 deletions(-)
diff --git a/drivers/s390/cio/qdio.h b/drivers/s390/cio/qdio.h
index 7f0aa95585a4..cd2df4ff8e0e 100644
--- a/drivers/s390/cio/qdio.h
+++ b/drivers/s390/cio/qdio.h
@@ -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 {
diff --git a/drivers/s390/cio/qdio_main.c b/drivers/s390/cio/qdio_main.c
index 0c1f186c6291..4fab8bba2cdd 100644
--- a/drivers/s390/cio/qdio_main.c
+++ b/drivers/s390/cio/qdio_main.c
@@ -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)