From: Joe Damato <jdamato@fastly.com>
To: Eric Dumazet <edumazet@google.com>
Cc: linux-kernel@vger.kernel.org, netdev@vger.kernel.org,
chuck.lever@oracle.com, jlayton@kernel.org,
linux-api@vger.kernel.org, brauner@kernel.org,
davem@davemloft.net, alexander.duyck@gmail.com,
sridhar.samudrala@intel.com, kuba@kernel.org,
willemdebruijn.kernel@gmail.com, weiwan@google.com,
David.Laight@aculab.com, arnd@arndb.de, sdf@google.com,
amritha.nambiar@intel.com,
Alexander Viro <viro@zeniv.linux.org.uk>, Jan Kara <jack@suse.cz>,
"open list:FILESYSTEMS (VFS and infrastructure)"
<linux-fsdevel@vger.kernel.org>
Subject: Re: [PATCH net-next v6 1/4] eventpoll: support busy poll per epoll instance
Date: Thu, 8 Feb 2024 10:06:02 -0800 [thread overview]
Message-ID: <20240208180601.GA3005@fastly.com> (raw)
In-Reply-To: <CANn89iJY8mTn3PViBvTh_DewUKWjc0z3cvJvr8AcQgcbWC4G0Q@mail.gmail.com>
On Thu, Feb 08, 2024 at 06:46:25PM +0100, Eric Dumazet wrote:
> On Mon, Feb 5, 2024 at 10:05 PM Joe Damato <jdamato@fastly.com> wrote:
> >
> > Allow busy polling on a per-epoll context basis. The per-epoll context
> > usec timeout value is preferred, but the pre-existing system wide sysctl
> > value is still supported if it specified.
> >
> > Signed-off-by: Joe Damato <jdamato@fastly.com>
> > ---
> > fs/eventpoll.c | 49 +++++++++++++++++++++++++++++++++++++++++++++----
> > 1 file changed, 45 insertions(+), 4 deletions(-)
> >
> > diff --git a/fs/eventpoll.c b/fs/eventpoll.c
> > index 3534d36a1474..ce75189d46df 100644
> > --- a/fs/eventpoll.c
> > +++ b/fs/eventpoll.c
> > @@ -227,6 +227,8 @@ struct eventpoll {
> > #ifdef CONFIG_NET_RX_BUSY_POLL
> > /* used to track busy poll napi_id */
> > unsigned int napi_id;
> > + /* busy poll timeout */
> > + u64 busy_poll_usecs;
> > #endif
> >
> > #ifdef CONFIG_DEBUG_LOCK_ALLOC
> > @@ -386,12 +388,44 @@ static inline int ep_events_available(struct eventpoll *ep)
> > READ_ONCE(ep->ovflist) != EP_UNACTIVE_PTR;
> > }
> >
> > +/**
> > + * busy_loop_ep_timeout - check if busy poll has timed out. The timeout value
> > + * from the epoll instance ep is preferred, but if it is not set fallback to
> > + * the system-wide global via busy_loop_timeout.
> > + *
> > + * @start_time: The start time used to compute the remaining time until timeout.
> > + * @ep: Pointer to the eventpoll context.
> > + *
> > + * Return: true if the timeout has expired, false otherwise.
> > + */
> > +static inline bool busy_loop_ep_timeout(unsigned long start_time, struct eventpoll *ep)
> > +{
> > +#ifdef CONFIG_NET_RX_BUSY_POLL
>
> It seems this local helper is only called from code compiled when
> CONFIG_NET_RX_BUSY_POLL
> is set.
>
> Not sure why you need an #ifdef here.
Thanks, you are right.
I'll move this down to be within CONFIG_NET_RX_BUSY_POLL and get rid of the
#ifdef for the v7.
Thanks for your review.
> > + unsigned long bp_usec = READ_ONCE(ep->busy_poll_usecs);
> > +
> > + if (bp_usec) {
> > + unsigned long end_time = start_time + bp_usec;
> > + unsigned long now = busy_loop_current_time();
> > +
> > + return time_after(now, end_time);
> > + } else {
> > + return busy_loop_timeout(start_time);
> > + }
> > +#endif
> > + return true;
> > +}
> > +
> > #ifdef CONFIG_NET_RX_BUSY_POLL
> > +static bool ep_busy_loop_on(struct eventpoll *ep)
> > +{
> > + return !!ep->busy_poll_usecs || net_busy_loop_on();
> > +}
> > +
> > static bool ep_busy_loop_end(void *p, unsigned long start_time)
> > {
> > struct eventpoll *ep = p;
> >
> > - return ep_events_available(ep) || busy_loop_timeout(start_time);
> > + return ep_events_available(ep) || busy_loop_ep_timeout(start_time, ep);
> > }
> >
> > /*
> > @@ -404,7 +438,7 @@ static bool ep_busy_loop(struct eventpoll *ep, int nonblock)
> > {
> > unsigned int napi_id = READ_ONCE(ep->napi_id);
> >
> > - if ((napi_id >= MIN_NAPI_ID) && net_busy_loop_on()) {
> > + if ((napi_id >= MIN_NAPI_ID) && ep_busy_loop_on(ep)) {
> > napi_busy_loop(napi_id, nonblock ? NULL : ep_busy_loop_end, ep, false,
> > BUSY_POLL_BUDGET);
> > if (ep_events_available(ep))
> > @@ -430,7 +464,8 @@ static inline void ep_set_busy_poll_napi_id(struct epitem *epi)
> > struct socket *sock;
> > struct sock *sk;
> >
> > - if (!net_busy_loop_on())
> > + ep = epi->ep;
> > + if (!ep_busy_loop_on(ep))
> > return;
> >
> > sock = sock_from_file(epi->ffd.file);
> > @@ -442,7 +477,6 @@ static inline void ep_set_busy_poll_napi_id(struct epitem *epi)
> > return;
> >
> > napi_id = READ_ONCE(sk->sk_napi_id);
> > - ep = epi->ep;
> >
> > /* Non-NAPI IDs can be rejected
> > * or
> > @@ -466,6 +500,10 @@ static inline void ep_set_busy_poll_napi_id(struct epitem *epi)
> > {
> > }
> >
> > +static inline bool ep_busy_loop_on(struct eventpoll *ep)
> > +{
> > + return false;
> > +}
> > #endif /* CONFIG_NET_RX_BUSY_POLL */
> >
> > /*
> > @@ -2058,6 +2096,9 @@ static int do_epoll_create(int flags)
> > error = PTR_ERR(file);
> > goto out_free_fd;
> > }
> > +#ifdef CONFIG_NET_RX_BUSY_POLL
> > + ep->busy_poll_usecs = 0;
> > +#endif
> > ep->file = file;
> > fd_install(fd, file);
> > return fd;
> > --
> > 2.25.1
> >
next prev parent reply other threads:[~2024-02-08 18:06 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-02-05 21:04 [PATCH net-next v6 0/4] Per epoll context busy poll support Joe Damato
2024-02-05 21:04 ` [PATCH net-next v6 1/4] eventpoll: support busy poll per epoll instance Joe Damato
2024-02-07 19:04 ` Jakub Kicinski
2024-02-07 19:14 ` Joe Damato
2024-02-07 20:11 ` Jakub Kicinski
2024-02-07 20:23 ` Joe Damato
2024-02-07 20:56 ` Jakub Kicinski
2024-02-08 17:46 ` Eric Dumazet
2024-02-08 18:06 ` Joe Damato [this message]
2024-02-05 21:04 ` [PATCH net-next v6 2/4] eventpoll: Add per-epoll busy poll packet budget Joe Damato
2024-02-07 19:04 ` Jakub Kicinski
2024-02-08 17:47 ` Eric Dumazet
2024-02-05 21:04 ` [PATCH net-next v6 3/4] eventpoll: Add per-epoll prefer busy poll option Joe Damato
2024-02-07 19:04 ` Jakub Kicinski
2024-02-08 17:49 ` Eric Dumazet
2024-02-05 21:04 ` [PATCH net-next v6 4/4] eventpoll: Add epoll ioctl for epoll_params Joe Damato
2024-02-07 8:37 ` Jiri Slaby
2024-02-07 18:50 ` Joe Damato
2024-02-07 19:07 ` Jakub Kicinski
2024-02-07 19:16 ` Joe Damato
2024-02-07 20:18 ` Jakub Kicinski
2024-02-06 18:51 ` [PATCH net-next v6 0/4] Per epoll context busy poll support Stanislav Fomichev
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