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Thu, 14 May 2026 03:06:44 -0700 (PDT) Received: from [192.168.88.32] ([216.128.9.106]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-48fdafb6145sm20539805e9.1.2026.05.14.03.06.43 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 14 May 2026 03:06:44 -0700 (PDT) Message-ID: <1b6d8eab-798b-4dce-be1b-adc93b0fd9fc@redhat.com> Date: Thu, 14 May 2026 12:06:42 +0200 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH net-next 2/2] net/sched: fq_codel: local packets no longer count against memory limit To: Eric Dumazet Cc: Jakub Kicinski , Jamal Hadi Salim , Simon Horman , Jiri Pirko , =?UTF-8?Q?Toke_H=C3=B8iland-J=C3=B8rgensen?= , netdev@vger.kernel.org, eric.dumazet@gmail.com, "David S . Miller" References: <20260512094859.3673997-1-edumazet@google.com> <20260512094859.3673997-3-edumazet@google.com> From: Paolo Abeni Content-Language: en-US In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 5/14/26 10:49 AM, Eric Dumazet wrote: > On Thu, May 14, 2026 at 1:24 AM Paolo Abeni wrote: >> On 5/12/26 11:48 AM, Eric Dumazet wrote: >>> Commit 95b58430abe7 ("fq_codel: add memory limitation per queue") >>> claimed that the 32Mb default was "reasonable even for heavy duty usages." >>> >>> In practice, this is not the case. >>> >>> Packets that are associated with local sockets sk_wmem_alloc >>> do not really need additional memory control. >>> >>> Signed-off-by: Eric Dumazet >>> --- >>> net/sched/sch_fq_codel.c | 2 +- >>> 1 file changed, 1 insertion(+), 1 deletion(-) >>> >>> diff --git a/net/sched/sch_fq_codel.c b/net/sched/sch_fq_codel.c >>> index 1b1de693d4c64a1f5f4e9e788371829dea91740e..71107dc52be799a14f370f2ad74d2eadd93992c1 100644 >>> --- a/net/sched/sch_fq_codel.c >>> +++ b/net/sched/sch_fq_codel.c >>> @@ -212,7 +212,7 @@ static int fq_codel_enqueue(struct sk_buff *skb, struct Qdisc *sch, >>> q->new_flow_count++; >>> WRITE_ONCE(flow->deficit, q->quantum); >>> } >>> - get_codel_cb(skb)->mem_usage = skb->truesize; >>> + get_codel_cb(skb)->mem_usage = is_skb_wmem(skb) ? 0 : skb->truesize; >>> q->memory_usage += get_codel_cb(skb)->mem_usage; >>> memory_limited = q->memory_usage > q->memory_limit; >>> qdisc_qlen_inc(sch); >> >> I *think* this patch is causing TDC self-tests failures: >> >> # not ok 704 a4bb - Test FQ_CODEL with HTB parent - force packet drop with empty queue >> # Could not match regex pattern. Verify command output: >> # qdisc fq_codel 10: parent 1:10 limit 10240p flows 1 quantum 1514 target 99us interval 999us memory_limit 1b ecn drop_batch 64 >> # Sent 490 bytes 5 pkt (dropped 0, overlimits 0 requeues 0) >> # backlog 0b 0p requeues 0 >> # maxpacket 98 drop_overlimit 0 new_flow_count 1 ecn_mark 0 >> # new_flows_len 1 old_flows_len 0 >> >> whole log at: >> >> https://github.com/p4tc-dev/tc-executor/tree/storage/artifacts/645644/1-tdc-sh >> >> Looking at the test code, I think the patch broke it, but the failures >> started a little afterward the patch merge, so I'm possibly >> misunderstanding something here. >> >> Thanks, >> >> Paolo >> > > It seems this test uses a memory limit of 1 byte. > > $TC qdisc add dev $DUMMY parent 1:10 handle 10: fq_codel memory_limit > 1 flows 1 target 0.1ms interval 1ms > > This might be a typo, I think they expected a limit of 0 packet. FTR, I think/agree a change to the self-tests would be preferable. /P