Re: [iptables PATCH v3 0/7] Improve xtables-restore performance

[Phil Sutter <phil@nwl.cc>]

On Thu, Oct 31, 2019 at 04:02:34PM +0100, Pablo Neira Ayuso wrote:
> On Thu, Oct 24, 2019 at 06:37:05PM +0200, Phil Sutter wrote:
> > This series speeds up xtables-restore calls with --noflush (typically
> > used to batch a few commands for faster execution) by preliminary input
> > inspection.
> > 
> > Before, setting --noflush flag would inevitably lead to full cache
> > population. With this series in place, if input can be fully buffered
> > and no commands requiring full cache is contained, no initial cache
> > population happens and each rule parsed will cause fetching of cache
> > bits as required.
> > 
> > The input buffer size is arbitrarily chosen to be 64KB.
> > 
> > Patches one and two prepare code for patch three which moves the loop
> > content parsing each line of input into a separate function. The
> > reduction of code indenting is used by patch four which deals with
> > needless line breaks.
> 
> For patches from 1 to 4 in this batch:
> 
> Acked-by: Pablo Neira Ayuso <pablo@netfilter.org>
> 
> > Patch five deals with another requirement of input buffering, namely
> > stripping newline characters from each line. This is not a problem by
> > itself, but add_param_to_argv() replaces them by nul-chars and so
> > strings stop being consistently terminated (some by a single, some by
> > two nul-chars).
> > 
> > Patch six then finally adds the buffering and caching decision code.
> > 
> > Patch seven is pretty unrelated but tests a specific behaviour of
> > *tables-restore I wasn't sure of at first.
> 
> Do you have any number?

Yes, I wrote a small benchmark based on some Kubernetes use-case. It
measures loading of dumps like:

| *nat
| :KUBE-SVC-23 - [0:0]
| :KUBE-SEP-23 - [0:0]
| -A KUBE-HOOK ! -s 10.128.0.0/14 -d 172.30.108.136/32 -p tcp -m comment --comment \"openshift-controller-manager/controller-manager:https cluster IP\" -m tcp --dport 443 -j KUBE-MARK-MASQ
| -A KUBE-HOOK -d 172.30.108.136/32 -p tcp -m comment --comment \"openshift-controller-manager/controller-manager:https cluster IP\" -m tcp --dport 443 -j KUBE-SVC-23
| -A KUBE-SVC-23 -j KUBE-SEP-23
| -A KUBE-SEP-23 -s 10.128.0.38/32 -j KUBE-MARK-MASQ
| -A KUBE-SEP-23 -p tcp -m tcp -j DNAT --to-destination 10.128.0.38:8443
| COMMIT

Into a ruleset with increasing size (created by repeating the snippet above):

size (*100) |	legacy     |   nft-pre	   |   nft-post
---------------------------------------------------------
1             .0040366426     .0079313714     .0025598650
10            .0146918664     .0459193868     .0025134858
25            .0361553334     .1195503778     .0024202904
50            .0699177362     .2547542626     .0024351612
75            .1062593206     .4078182120     .0024362044
100           .1614045514     .5636617378     .0024195190

The graph says it all: http://nwl.cc/~n0-1/kube.png

Cheers, Phil