On Sat, 2016-06-18 at 11:24 -0400, Jamal Hadi Salim wrote:
> On 16-06-18 11:16 AM, Eric Dumazet wrote:
>
> >> Given an update/replace of an action is such a rare occassion, what
> >> is wrong with init doing a spin lock on existing action?
> >> Sure, there is performance impact on fast path at tha
On 16-06-18 11:16 AM, Eric Dumazet wrote:
Given an update/replace of an action is such a rare occassion, what
is wrong with init doing a spin lock on existing action?
Sure, there is performance impact on fast path at that point - but:
as established update/replace is _a rare occassion_ ;->
The
On Sat, 2016-06-18 at 09:45 -0400, Jamal Hadi Salim wrote:
> On 16-06-17 06:03 PM, Eric Dumazet wrote:
> > On Fri, Jun 17, 2016 at 2:59 PM, Cong Wang wrote:
> >
> >> Generally speaking I worry about we change multiple fields in a struct
> >> meanwhile we could still read them any time in the middl
On 16-06-17 06:03 PM, Eric Dumazet wrote:
On Fri, Jun 17, 2016 at 2:59 PM, Cong Wang wrote:
Generally speaking I worry about we change multiple fields in a struct
meanwhile we could still read them any time in the middle, we may
get them correct for some easy case, but it is hard to insure the
On Fri, Jun 17, 2016 at 2:59 PM, Cong Wang wrote:
> Generally speaking I worry about we change multiple fields in a struct
> meanwhile we could still read them any time in the middle, we may
> get them correct for some easy case, but it is hard to insure the
> correctness when the struct becomes
On Fri, Jun 17, 2016 at 2:40 PM, Eric Dumazet wrote:
> On Fri, Jun 17, 2016 at 2:35 PM, Cong Wang wrote:
>> On Fri, Jun 17, 2016 at 2:24 PM, Eric Dumazet wrote:
>>> Well, I added a READ_ONCE() to read tcf_action once.
>>>
>>> Adding rcu here would mean adding a pointer and extra cache line, to
>
On Fri, Jun 17, 2016 at 2:35 PM, Cong Wang wrote:
> On Fri, Jun 17, 2016 at 2:24 PM, Eric Dumazet wrote:
>> Well, I added a READ_ONCE() to read tcf_action once.
>>
>> Adding rcu here would mean adding a pointer and extra cache line, to
>> deref the values.
>>
>> IMHO the race here has no effect .
On Fri, Jun 17, 2016 at 2:24 PM, Eric Dumazet wrote:
> Well, I added a READ_ONCE() to read tcf_action once.
>
> Adding rcu here would mean adding a pointer and extra cache line, to
> deref the values.
>
> IMHO the race here has no effect . You either read the old or new value.
Sure, the point is
On Fri, Jun 17, 2016 at 2:03 PM, Cong Wang wrote:
> Hi, Eric
>
> During code review, I notice we might have some problem after we go
> lockless for the fast path in act_mirred.
>
> That is, what prevents us from the following possible race condition?
>
> change a standalone action with tcf_mirred_
Hi, Eric
During code review, I notice we might have some problem after we go
lockless for the fast path in act_mirred.
That is, what prevents us from the following possible race condition?
change a standalone action with tcf_mirred_init():
// search for an existing action in hash
// found it
On 7/6/15 5:18 AM, Eric Dumazet wrote:
Like act_gact, act_mirred can be lockless in packet processing
1) Use percpu stats
2) update lastuse only every clock tick to avoid false sharing
3) use rcu to protect tcfm_dev
4) Remove spinlock usage, as it is no longer needed.
Next step : add multi queu
ifb patch seems to work very well ;)
# tc -s -d qd sh dev ifb10
qdisc mq 1: root
Sent 190952 bytes 31798616 pkt (dropped 0, overlimits 0 requeues 0)
backlog 29460b 491p requeues 0
qdisc netem 8002: parent 1:1 limit 10 delay 3.0ms
Sent 238320936 bytes 3971225 pkt (dropped 0, overlimits 0
On Mon, Jul 6, 2015 at 2:53 PM, Jamal Hadi Salim wrote:
> cant wait for the multi queue ifb.
>
Yeah, me too ;)
Do not try this on a production host :
ip link add ifb10 numtxqueues 100 type ifb
[284151.950695] kernel BUG at /build/buildd/linux-3.13.0/net/core/dev.c:5868!
[284151.950762] in
On 07/06/15 08:18, Eric Dumazet wrote:
Like act_gact, act_mirred can be lockless in packet processing
1) Use percpu stats
2) update lastuse only every clock tick to avoid false sharing
3) use rcu to protect tcfm_dev
4) Remove spinlock usage, as it is no longer needed.
Next step : add multi queu
Like act_gact, act_mirred can be lockless in packet processing
1) Use percpu stats
2) update lastuse only every clock tick to avoid false sharing
3) use rcu to protect tcfm_dev
4) Remove spinlock usage, as it is no longer needed.
Next step : add multi queue capability to ifb device
Signed-off-by
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