* Re: coping with memory limitations and packet flooding in codel and fq_codel [not found] <CAA93jw7=K8Vvp6N5qYZ8gaODaFyZtAEjGyQe2BDh9-RBsvVHcQ@mail.gmail.com> @ 2012-08-21 8:38 ` Eric Dumazet 2012-08-21 10:27 ` Andrew McGregor 0 siblings, 1 reply; 3+ messages in thread From: Eric Dumazet @ 2012-08-21 8:38 UTC (permalink / raw) To: Dave Taht; +Cc: netdev, codel On Mon, 2012-08-20 at 14:05 -0700, Dave Taht wrote: > We've had a raft of deployment questions regarding fq_codel, memory > use, and the impact of unresponsive flows > over on the cerowrt development list. > > sort of summary of the thread here, with some codel related ideas > > https://lists.bufferbloat.net/pipermail/cerowrt-devel/2012-August/000423.html > > some early data on wifi interactions here > > https://lists.bufferbloat.net/pipermail/cerowrt-devel/2012-August/000407.html > CC netdev codel / fq_codel have a packet limit per qdisc, like any other linux qdisc. DEFAULT_CODEL_LIMIT = 1000 packets fq_codel : 10240 packets For memory constrained boxes, it would be wise to add a 'truesize' limit Not a bytes limit based on skb->len sum, because a skb->len = 60 bytes packet might consume far more memory (more than 2 Kbytes) ath9k driver is known to deliver very fat skbs (skb->truesize is too big) One 'other way' to limit bloat would be to reallocate skbs when one qdisc begins to use more than 25 % of its truesize limit enqueue(q, skb) { if (q->truesize_sum > q->truesize_limit / 4) skb = skb_reduce_truesize(skb, GFP_ATOMIC); ... } This is what some drivers already do in their rx handler (this is called copybreak), but this would do the copy (and extra cpu cost) only in stress situations. Note : we also have a very big struct skb_shared_info (320 bytes), we probably could shrink it for packets without fragments. ^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: coping with memory limitations and packet flooding in codel and fq_codel 2012-08-21 8:38 ` coping with memory limitations and packet flooding in codel and fq_codel Eric Dumazet @ 2012-08-21 10:27 ` Andrew McGregor 2012-08-21 10:50 ` Eric Dumazet 0 siblings, 1 reply; 3+ messages in thread From: Andrew McGregor @ 2012-08-21 10:27 UTC (permalink / raw) To: Eric Dumazet; +Cc: netdev, codel [-- Attachment #1.1: Type: text/plain, Size: 192 bytes --] On 21/08/2012, at 8:38 PM, Eric Dumazet <eric.dumazet@gmail.com> wrote: > ath9k driver is known to deliver very fat skbs (skb->truesize is too > big) What would it take to fix this? Andrew [-- Attachment #1.2: smime.p7s --] [-- Type: application/pkcs7-signature, Size: 2330 bytes --] [-- Attachment #2: Type: text/plain, Size: 140 bytes --] _______________________________________________ Codel mailing list Codel@lists.bufferbloat.net https://lists.bufferbloat.net/listinfo/codel ^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: coping with memory limitations and packet flooding in codel and fq_codel 2012-08-21 10:27 ` Andrew McGregor @ 2012-08-21 10:50 ` Eric Dumazet 0 siblings, 0 replies; 3+ messages in thread From: Eric Dumazet @ 2012-08-21 10:50 UTC (permalink / raw) To: Andrew McGregor; +Cc: netdev, codel On Tue, 2012-08-21 at 22:27 +1200, Andrew McGregor wrote: > On 21/08/2012, at 8:38 PM, Eric Dumazet <eric.dumazet@gmail.com> wrote: > > > ath9k driver is known to deliver very fat skbs (skb->truesize is too > > big) > > What would it take to fix this? > > Andrew Someone could use the following : https://gerrit.chromium.org/gerrit/#/c/18412/ ^ permalink raw reply [flat|nested] 3+ messages in thread
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2012-08-21 8:38 ` coping with memory limitations and packet flooding in codel and fq_codel Eric Dumazet
2012-08-21 10:27 ` Andrew McGregor
2012-08-21 10:50 ` Eric Dumazet
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