Re: [PATCH net/for-next V1 1/1] IB/ipoib: break linkage to neighbouring system

On 7/19/2012 6:24 PM, Christoph Lameter wrote:

On Thu, 19 Jul 2012, Shlomo Pongartz wrote:

quoted

The garbage collection and stale times follow the default ipv4/6 neigh.default.gc_yyy
sysctl values, for example

net.ipv4.neigh.default.gc_interval = 30
net.ipv4.neigh.default.gc_stale_time = 60

If given access to these values from IPoIB, we will be happy
to integrate them into that logic

It looks like the values are hardcoded right now.

Two points here,

1s, they are indeed hard-coded since there's no define/enum
that holds their default values (or maybe we should add one now?), see
this code snippest from net/ipv4/arp.c

        .gc_interval    = 30 * HZ,
        .gc_thresh1     = 128,
        .gc_thresh2     = 512,
        .gc_thresh3     = 1024,

2nd, and even more interesting, the little challenge here is how
to integrate with the sysctl's that allow for changing these values,
the mechanism that uses neigh_sysctl_table in net/core/neighbour.c isn't
exported to the rest of the world. And there's no point to define new
sysctl entries just for managing the IPoIB neighbours, ideas welcome.

quoted

Please clarify what do you mean by group expiration.

If you have neighbor expiration periods of 4 hrs and it is necessary to
run the expiration logic then please expire all the neighbor entries due a
certain period after that as well to avoid running the expiration again in
the next minute or so.

This is still a bit unclear here... do you mean to say that at a certain point in time,
**all** entries need to be deleted irrelevant of their (jiffies) age? why?

I guess the fuzz factor needs to scale depending on the expiration period.

and this is what happens now, the factor is 0.5, entry would be deleted when
if  (60m <= unused < 90s) holds

Or.
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