netdev - RE: [patch net-next 2/3] net/sched: Change cls

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Date:   Tue, 29 Aug 2017 03:25:35 +0000
From:   Chris Mi <chrism@...lanox.com>
To:     Simon Horman <simon.horman@...ronome.com>
CC:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "jhs@...atatu.com" <jhs@...atatu.com>,
        "xiyou.wangcong@...il.com" <xiyou.wangcong@...il.com>,
        "jiri@...nulli.us" <jiri@...nulli.us>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "mawilcox@...rosoft.com" <mawilcox@...rosoft.com>
Subject: RE: [patch net-next 2/3] net/sched: Change cls_flower to use IDR



> -----Original Message-----
> From: Simon Horman [mailto:simon.horman@...ronome.com]
> Sent: Monday, August 28, 2017 7:37 PM
> To: Chris Mi <chrism@...lanox.com>
> Cc: netdev@...r.kernel.org; jhs@...atatu.com;
> xiyou.wangcong@...il.com; jiri@...nulli.us; davem@...emloft.net;
> mawilcox@...rosoft.com
> Subject: Re: [patch net-next 2/3] net/sched: Change cls_flower to use IDR
> 
> On Mon, Aug 28, 2017 at 02:41:16AM -0400, Chris Mi wrote:
> > Currently, all filters with the same priority are linked in a doubly
> > linked list. Every filter should have a unique handle. To make the
> > handle unique, we need to iterate the list every time to see if the
> > handle exists or not when inserting a new filter. It is time-consuming.
> > For example, it takes about 5m3.169s to insert 64K rules.
> >
> > This patch changes cls_flower to use IDR. With this patch, it takes
> > about 0m1.127s to insert 64K rules. The improvement is huge.
> 
> Very nice :)
> 
> > But please note that in this testing, all filters share the same action.
> > If every filter has a unique action, that is another bottleneck.
> > Follow-up patch in this patchset addresses that.
> >
> > Signed-off-by: Chris Mi <chrism@...lanox.com>
> > Signed-off-by: Jiri Pirko <jiri@...lanox.com>
> > ---
> >  net/sched/cls_flower.c | 55
> > +++++++++++++++++++++-----------------------------
> >  1 file changed, 23 insertions(+), 32 deletions(-)
> >
> > diff --git a/net/sched/cls_flower.c b/net/sched/cls_flower.c index
> > bd9dab4..3d041d2 100644
> > --- a/net/sched/cls_flower.c
> > +++ b/net/sched/cls_flower.c
> 
> ...
> 
> > @@ -890,6 +870,7 @@ static int fl_change(struct net *net, struct sk_buff
> *in_skb,
> >  	struct cls_fl_filter *fnew;
> >  	struct nlattr **tb;
> >  	struct fl_flow_mask mask = {};
> > +	unsigned long idr_index;
> >  	int err;
> >
> >  	if (!tca[TCA_OPTIONS])
> > @@ -920,13 +901,21 @@ static int fl_change(struct net *net, struct sk_buff
> *in_skb,
> >  		goto errout;
> >
> >  	if (!handle) {
> > -		handle = fl_grab_new_handle(tp, head);
> > -		if (!handle) {
> > -			err = -EINVAL;
> > +		err = idr_alloc_ext(&head->handle_idr, fnew, &idr_index,
> > +				    1, 0x80000000, GFP_KERNEL);
> > +		if (err)
> >  			goto errout;
> > -		}
> > +		fnew->handle = idr_index;
> > +	}
> > +
> > +	/* user specifies a handle and it doesn't exist */
> > +	if (handle && !fold) {
> > +		err = idr_alloc_ext(&head->handle_idr, fnew, &idr_index,
> > +				    handle, handle + 1, GFP_KERNEL);
> > +		if (err)
> > +			goto errout;
> > +		fnew->handle = idr_index;
> >  	}
> > -	fnew->handle = handle;
> >
> >  	if (tb[TCA_FLOWER_FLAGS]) {
> >  		fnew->flags = nla_get_u32(tb[TCA_FLOWER_FLAGS]);
> > @@ -980,6 +969,8 @@ static int fl_change(struct net *net, struct sk_buff
> *in_skb,
> >  	*arg = fnew;
> >
> >  	if (fold) {
> > +		fnew->handle = handle;
> 
> Can it be the case that fold is non-NULL and handle is zero?
> The handling of that case seem to have changed in this patch.
I don't think that could happen.  In function tc_ctl_tfilter(),

fl_get() will be called.  If handle is zero, fl_get() will return NULL.
That means fold is NULL.

> 
> > +		idr_replace_ext(&head->handle_idr, fnew, fnew->handle);
> >  		list_replace_rcu(&fold->list, &fnew->list);
> >  		tcf_unbind_filter(tp, &fold->res);
> >  		call_rcu(&fold->rcu, fl_destroy_filter);
> > --
> > 1.8.3.1
> >