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Subject[PATCH net-next 1/10] cxgb3: ring rx door bell less frequently
Date
From: Divy Le Ray <divy@chelsio.com>

Ring free lists door bell less frequently,
specifically every quarter of the active FL
size.

Signed-off-by: Divy Le Ray <divy@chelsio.com>
---

drivers/net/cxgb3/adapter.h | 1 +
drivers/net/cxgb3/sge.c | 32 ++++++++++++++++++++++++--------
2 files changed, 25 insertions(+), 8 deletions(-)

diff --git a/drivers/net/cxgb3/adapter.h b/drivers/net/cxgb3/adapter.h
index fbe1569..95dce48 100644
--- a/drivers/net/cxgb3/adapter.h
+++ b/drivers/net/cxgb3/adapter.h
@@ -91,6 +91,7 @@ struct rx_sw_desc;
struct sge_fl { /* SGE per free-buffer list state */
unsigned int buf_size; /* size of each Rx buffer */
unsigned int credits; /* # of available Rx buffers */
+ unsigned int pend_cred; /* new buffers since last FL DB ring */
unsigned int size; /* capacity of free list */
unsigned int cidx; /* consumer index */
unsigned int pidx; /* producer index */
diff --git a/drivers/net/cxgb3/sge.c b/drivers/net/cxgb3/sge.c
index 8205aa4..882beaf 100644
--- a/drivers/net/cxgb3/sge.c
+++ b/drivers/net/cxgb3/sge.c
@@ -63,6 +63,10 @@
#define SGE_RX_DROP_THRES 16

/*
+ * Max number of Rx buffers we replenish at a time.
+ */
+#define MAX_RX_REFILL 16U
+/*
* Period of the Tx buffer reclaim timer. This timer does not need to run
* frequently as Tx buffers are usually reclaimed by new Tx packets.
*/
@@ -423,6 +427,14 @@ static int alloc_pg_chunk(struct sge_fl *q, struct rx_sw_desc *sd, gfp_t gfp,
return 0;
}

+static inline void ring_fl_db(struct adapter *adap, struct sge_fl *q)
+{
+ if (q->pend_cred >= q->credits / 4) {
+ q->pend_cred = 0;
+ t3_write_reg(adap, A_SG_KDOORBELL, V_EGRCNTX(q->cntxt_id));
+ }
+}
+
/**
* refill_fl - refill an SGE free-buffer list
* @adapter: the adapter
@@ -478,19 +490,19 @@ nomem: q->alloc_failed++;
sd = q->sdesc;
d = q->desc;
}
- q->credits++;
count++;
}
- wmb();
- if (likely(count))
- t3_write_reg(adap, A_SG_KDOORBELL, V_EGRCNTX(q->cntxt_id));
+
+ q->credits += count;
+ q->pend_cred += count;
+ ring_fl_db(adap, q);

return count;
}

static inline void __refill_fl(struct adapter *adap, struct sge_fl *fl)
{
- refill_fl(adap, fl, min(16U, fl->size - fl->credits),
+ refill_fl(adap, fl, min(MAX_RX_REFILL, fl->size - fl->credits),
GFP_ATOMIC | __GFP_COMP);
}

@@ -515,13 +527,15 @@ static void recycle_rx_buf(struct adapter *adap, struct sge_fl *q,
wmb();
to->len_gen = cpu_to_be32(V_FLD_GEN1(q->gen));
to->gen2 = cpu_to_be32(V_FLD_GEN2(q->gen));
- q->credits++;

if (++q->pidx == q->size) {
q->pidx = 0;
q->gen ^= 1;
}
- t3_write_reg(adap, A_SG_KDOORBELL, V_EGRCNTX(q->cntxt_id));
+
+ q->credits++;
+ q->pend_cred++;
+ ring_fl_db(adap, q);
}

/**
@@ -732,7 +746,9 @@ recycle:
return skb;
}

- if (unlikely(fl->credits < drop_thres))
+ if (unlikely(fl->credits < drop_thres) &&
+ refill_fl(adap, fl, min(MAX_RX_REFILL, fl->size - fl->credits - 1),
+ GFP_ATOMIC | __GFP_COMP) == 0)
goto recycle;

use_orig_buf:


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