Re: [PATCH net 2/2] conntrack: enable to tune gc parameters
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From: Nicolas Dichtel <hidden>
Date: 2016-10-10 15:24:25
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netfilter-devel
Le 10/10/2016 à 16:04, Florian Westphal a écrit :
Nicolas Dichtel [off-list ref] wrote:quoted
After commit b87a2f9199ea ("netfilter: conntrack: add gc worker to remove timed-out entries"), netlink conntrack deletion events may be sent with a huge delay. It could be interesting to let the user tweak gc parameters depending on its use case.Hmm, care to elaborate? I am not against doing this but I'd like to hear/read your use case. The expectation is that in almot all cases eviction will happen from packet path. The gc worker is jusdt there for case where a busy system goes idle.
It was precisely that case. After a period of activity, the event is sent a long time after the timeout. If the router does not manage a lot of flows, why not trying to parse more entries instead of the default 1/64 of the table? In fact, I don't understand why using GC_MAX_BUCKETS_DIV instead of using always GC_MAX_BUCKETS whatever the size of the table is.
quoted
+nf_conntrack_gc_max_evicts - INTEGER + The maximum number of entries to be evicted during a run of gc. + This sysctl is only writeable in the initial net namespace.Hmmm, do you have any advice on sizing this one?
In fact, no ;-) I really hesitate to expose the four values or just a subset. My goal was also to get feedback. I can remove this one.
I think a better change might be (instead of adding htis knob) to resched the gc worker for immediate re-executaion in case the entire "budget" was used. What do you think?
Even if it's not directly related to my problem, I think it's a good idea.
quoted hunk ↗ jump to hunk
diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c --- a/net/netfilter/nf_conntrack_core.c +++ b/net/netfilter/nf_conntrack_core.c@@ -983,7 +983,7 @@ static void gc_worker(struct work_struct *work) return; ratio = scanned ? expired_count * 100 / scanned : 0; - if (ratio >= 90) + if (ratio >= 90 || expired_count == GC_MAX_EVICTS) next_run = 0;