I notice that netif_rx (net/core/dev.c) discards packets when it's
in throttle mode. However, before it does this the driver has already
wasted a lot of time allocating the skb, calling eth_type_trans, etc.
That effort could be saved if the driver checked throttle first.
Sample diff:
--- /usr/src/linux-2.4.18-clean/drivers/net/8139too.c Mon Feb 25 11:37:59 2002
+++ /usr/src/linux-2.4.18/drivers/net/8139too.c Wed Apr 16 23:30:30 2003
@@ -1908,6 +1908,11 @@
return;
}
+ if (softnet_data[smp_processor_id()].throttle) {
+ dev->last_rx = jiffies;
+ netdev_rx_stat[smp_processor_id()].dropped++;
+ } else {
+
/* Malloc up new buffer, compatible with net-2e. */
/* Omit the four octet CRC from the length. */
@@ -1936,6 +1941,7 @@
dev->name);
tp->stats.rx_dropped++;
}
+ }
cur_rx = (cur_rx + rx_size + 4 + 3) & ~3;
RTL_W16 (RxBufPtr, cur_rx - 16);
Hmm, now that I notice, there is one small change in semantics here.
Before every packet that was counted by netdev_rx_stat[].dropped had
also been counted in stats.rx_bytes and rx_packets and this is no
longer the case. If that bothers you then perhaps there should just
be a separate counter for packets dropped like this.
In my limited experimentation this sort of change has significantly
increased the number of packets I could process when they were
arriving too fast.
Please cc me on replies.
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This archive was generated by hypermail 2b29 : Wed Apr 23 2003 - 22:00:21 EST