Re: [PATCH v2] neighbour: Don't let neigh_forced_gc() disable preemption for long

[Doug Anderson]

Hi,

On Wed, Dec 6, 2023 at 9:51 AM David Ahern <dsahern@xxxxxxxxxx> wrote:
>
> On 12/6/23 10:39 AM, Stephen Hemminger wrote:
> > On Wed,  6 Dec 2023 03:38:33 +0000
> > Judy Hsiao <judyhsiao@xxxxxxxxxxxx> wrote:
> >
> >> diff --git a/net/core/neighbour.c b/net/core/neighbour.c
> >> index df81c1f0a570..552719c3bbc3 100644
> >> --- a/net/core/neighbour.c
> >> +++ b/net/core/neighbour.c
> >> @@ -253,9 +253,11 @@ static int neigh_forced_gc(struct neigh_table *tbl)
> >>  {
> >>      int max_clean = atomic_read(&tbl->gc_entries) -
> >>                      READ_ONCE(tbl->gc_thresh2);
> >> +    u64 tmax = ktime_get_ns() + NSEC_PER_MSEC;
> >>      unsigned long tref = jiffies - 5 * HZ;
> >>      struct neighbour *n, *tmp;
> >>      int shrunk = 0;
> >> +    int loop = 0;
> >>
> >>      NEIGH_CACHE_STAT_INC(tbl, forced_gc_runs);
> >>
> >> @@ -278,11 +280,16 @@ static int neigh_forced_gc(struct neigh_table *tbl)
> >>                              shrunk++;
> >>                      if (shrunk >= max_clean)
> >>                              break;
> >> +                    if (++loop == 16) {
> >
> > Overall looks good.
> > Minor comments:
> >       - loop count should probably be unsigned
> >         - the magic constant 16 should be a sysctl tuneable
>
> A tunable is needed here; the loop counter is just to keep the overhead
> of the ktime_get_ns call in check.

>From context, I'm going to assume you meant a tunable is _NOT_ needed here. ;-)

-Doug