Re: [PATCH net-next] fq_codel: add memory limitation per queue

From: Eric Dumazet <redacted>
Date: Fri, 06 May 2016 08:55:12 -0700

From: Eric Dumazet <redacted>

On small embedded routers, one wants to control maximal amount of
memory used by fq_codel, instead of controlling number of packets or
bytes, since GRO/TSO make these not practical.

Assuming skb->truesize is accurate, we have to keep track of
skb->truesize sum for skbs in queue.

This patch adds a new TCA_FQ_CODEL_MEMORY_LIMIT attribute.

I chose a default value of 32 MBytes, which looks reasonable even
for heavy duty usages. (Prior fq_codel users should not be hurt
when they upgrade their kernels)

Two fields are added to tc_fq_codel_qd_stats to report :
 - Current memory usage
 - Number of drops caused by memory limits

# tc qd replace dev eth1 root est 1sec 4sec fq_codel memory_limit 4M
..
# tc -s -d qd sh dev eth1
qdisc fq_codel 8008: root refcnt 257 limit 10240p flows 1024
 quantum 1514 target 5.0ms interval 100.0ms memory_limit 4Mb ecn 
 Sent 2083566791363 bytes 1376214889 pkt (dropped 4994406, overlimits 0
requeues 21705223) 
 rate 9841Mbit 812549pps backlog 3906120b 376p requeues 21705223 
  maxpacket 68130 drop_overlimit 4994406 new_flow_count 28855414
  ecn_mark 0 memory_used 4190048 drop_overmemory 4994406
  new_flows_len 1 old_flows_len 177


Signed-off-by: Eric Dumazet <redacted>

Applied, thanks Eric.