From: Judy Hsiao Date: Wed, 6 Dec 2023 03:38:33 +0000 (+0000) Subject: neighbour: Don't let neigh_forced_gc() disable preemption for long X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=e5dc5afff62f3e97e86c3643ec9fcad23de4f2d3;p=linux.git neighbour: Don't let neigh_forced_gc() disable preemption for long We are seeing cases where neigh_cleanup_and_release() is called by neigh_forced_gc() many times in a row with preemption turned off. When running on a low powered CPU at a low CPU frequency, this has been measured to keep preemption off for ~10 ms. That's not great on a system with HZ=1000 which expects tasks to be able to schedule in with ~1ms latency. Suggested-by: Douglas Anderson Signed-off-by: Judy Hsiao Reviewed-by: David Ahern Reviewed-by: Eric Dumazet Reviewed-by: Douglas Anderson Signed-off-by: David S. Miller --- diff --git a/net/core/neighbour.c b/net/core/neighbour.c index df81c1f0a5704..552719c3bbc3d 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) { + if (ktime_get_ns() > tmax) + goto unlock; + loop = 0; + } } } WRITE_ONCE(tbl->last_flush, jiffies); - +unlock: write_unlock_bh(&tbl->lock); return shrunk;