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Message-ID: <65e983c5155fa_f5b792941b@willemb.c.googlers.com.notmuch>
Date: Thu, 07 Mar 2024 04:07:17 -0500
From: Willem de Bruijn <willemdebruijn.kernel@...il.com>
To: Willem de Bruijn <willemdebruijn.kernel@...il.com>,
Marcelo Tosatti <mtosatti@...hat.com>,
netdev@...r.kernel.org,
linux-kernel@...r.kernel.org
Cc: Willem de Bruijn <willemdebruijn.kernel@...il.com>,
Jakub Kicinski <kuba@...nel.org>,
Eric Dumazet <edumazet@...gle.com>,
Frederic Weisbecker <frederic@...nel.org>,
Valentin Schneider <vschneid@...hat.com>,
Paolo Abeni <pabeni@...hat.com>
Subject: Re: [PATCH net-next -v3] net/core/dev.c: enable timestamp static key
if CPU isolation is configured
Willem de Bruijn wrote:
> Marcelo Tosatti wrote:
> >
> > For systems that use CPU isolation (via nohz_full), creating or destroying
> > a socket with
>
> - timestamping (SOCK_TIMESTAMPING_RX_SOFTWARE) might cause a
> + SO_TIMESTAMP, SO_TIMESTAMPNS or SO_TIMESTAMPING with flag
> + SOF_TIMESTAMPING_RX_SOFTWARE will cause a
>
> > static key to be enabled/disabled. This in turn causes undesired
> > IPIs to isolated CPUs.
> >
> > So enable the static key unconditionally, if CPU isolation is enabled,
> > thus avoiding the IPIs.
> >
> > Signed-off-by: Marcelo Tosatti <mtosatti@...hat.com>
>
> > diff --git a/net/core/dev.c b/net/core/dev.c
> > index c588808be77f..15a32f5900e6 100644
> > --- a/net/core/dev.c
> > +++ b/net/core/dev.c
> > @@ -155,6 +155,7 @@
> > #include <net/netdev_rx_queue.h>
> > #include <net/page_pool/types.h>
> > #include <net/page_pool/helpers.h>
> > +#include <linux/sched/isolation.h>
> >
> > #include "dev.h"
> > #include "net-sysfs.h"
> > @@ -11851,3 +11852,14 @@ static int __init net_dev_init(void)
> > }
> >
> > subsys_initcall(net_dev_init);
> > +
> > +static int __init net_dev_late_init(void)
> > +{
> > + /* avoid static key IPIs to isolated CPUs */
> > + if (housekeeping_enabled(HK_TYPE_MISC))
> > + net_enable_timestamp();
> > +
> > + return 0;
> > +}
> > +
> > +late_initcall(net_dev_late_init);
> >
>
> Can this be included in the existing net_dev_init
> subsys_initcall?
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