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In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 17/07/2024 22:40, Sabrina Dubroca wrote: >>>> +/** >>>> + * ovpn_peer_keepalive_recv_reset - reset keepalive timeout >>>> + * @peer: peer for which the timeout should be reset >>>> + * >>>> + * To be invoked upon reception of an authenticated packet from peer in order >>>> + * to report valid activity and thus reset the keepalive timeout >>>> + */ >>>> +static inline void ovpn_peer_keepalive_recv_reset(struct ovpn_peer *peer) >>>> +{ >>>> + u32 delta = msecs_to_jiffies(peer->keepalive_timeout * MSEC_PER_SEC); >>>> + >>>> + if (unlikely(!delta)) >>>> + return; >>>> + >>>> + mod_timer(&peer->keepalive_recv, jiffies + delta); >>> >>> This (and ovpn_peer_keepalive_xmit_reset) is going to be called for >>> each packet. I wonder how well the timer subsystem deals with one >>> timer getting updated possibly thousands of time per second. >>> >> >> May it even introduce some performance penalty? > > That's what I was worried about, yes. > > I asked Paolo, he suggested checking that we're actually doing any > change to the timer: > > if (new_timeout_time != old_timeout_time) > mod_timer(...) > > This would reduce the update frequency to one per jiffy, which should > be acceptable. > >> Maybe we should get rid of the timer object and introduce a periodic (1s) >> worker which checks some last_recv timestamp on every known peer? >> What do you think? > > That should work, or the workqueue like Eyal is saying. I will go with Eyal's approach. This way we also eliminate any timer related operation from the fast path. Cheers! -- Antonio Quartulli OpenVPN Inc.