Date: Wed, 9 Feb 2011 19:45:52 +0100 From: Michael Tuexen <tuexen@freebsd.org> To: Jack Vogel <jfvogel@gmail.com> Cc: Karim Fodil-Lemelin <fodillemlinkarim@gmail.com>, Pyun YongHyeon <pyunyh@gmail.com>, freebsd-net@freebsd.org, beezarliu <beezarliu@yahoo.com.cn> Subject: Re: igb driver RX (was TX) hangs when out of mbuf clusters Message-ID: <12838373-FE96-443E-8979-AF5408705BF0@freebsd.org> In-Reply-To: <AANLkTinMHSTMqskxTz2d3ysooadF5AwjTOGHnAbOhAj-@mail.gmail.com> References: <AANLkTikrjkHDaBq%2Bx6MTZhzOeqWA=xtFpqQPsthFGmuf@mail.gmail.com> <D70A2DA6-23B7-442D-856C-4267359D66A5@lurchi.franken.de> <AANLkTinLg6QZz67e3Hhda-bzTX69XWNcdEkr3EZHFmSZ@mail.gmail.com> <AANLkTikMuFRY=W0%2BVtGKdWkJcOFVbdy=OOZNe_xFUC3R@mail.gmail.com> <AANLkTin5DZBnr_VcXRyUmpcH2Gsr3GuaW4EsBtKJ6omd@mail.gmail.com> <AANLkTinaftP09MxxpXQwhLaO3dybSep2q4SWZRP4ycHB@mail.gmail.com> <AANLkTikaFRh-3OK0xjO8a%2BnY5aoPnMVFGPCnR1CGDVPk@mail.gmail.com> <F06CCA42-610F-41CA-897F-7029CCAE991B@freebsd.org> <AANLkTinMHSTMqskxTz2d3ysooadF5AwjTOGHnAbOhAj-@mail.gmail.com>
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On Feb 9, 2011, at 6:35 PM, Jack Vogel wrote:
> OK, but the question is why does the ring get totally consumed this =
way, the
> ring has 1024 descriptors, it seems unintuitive that that whole =
quantity can be
> used without some being recharged. Do you see the system mbuf pool =
being
> depleted at the same time?
That was the test case I created: I set up a server accepting =
connections
but not reading anything. So the driver passes the mbufs to the =
transport
stack and they are not consumed. Then the problem occurs. Then I kill =
the
server. Now there are mbufs available again, but the driver doesn't =
know.
I had the impression that these were the circumstances in which the =
problem
showed up (mbuf allocations failing).
>=20
> Since you can reproduce it, do me a favor, in rxeof, change the =
processed
> value from 8 to 4 and then 1, effectively call refresh every =
descriptor, see if
> that eliminates the issue.
I will do. Need to see if I can do it remotely, since I'm not in my lab
right now. Can do it tomorrow for sure.
But I do not think that this solves the problem, since I did the things
very slowly and you call it at least when you are leaving rxeof.
Best regards
Michael
>=20
> Thanks for your help,
>=20
> Jack
>=20
>=20
> On Wed, Feb 9, 2011 at 2:36 AM, Michael Tuexen <tuexen@freebsd.org> =
wrote:
> Hi Jack,
>=20
> I could recreate the problem. When the problem occurs, we see
>=20
> rx_nxt_check =3D n
> rx_nxt_refresh =3D n + 1
>=20
> (This was also reported in a mail from Karim)
>=20
> This means that the *whole* receive ring has no buffers anymore. This =
can
> occur if, for some amount of time, no clusters are available.
>=20
> Now outside of the driver, at some point of time, clusters are freed.
> I don't think that igb_refresh_mbufs() gets called, since it only gets
> called from igb_rxeof(), which gets called when a packet has been =
received,
> which can not happen since the receive ring is empty. So how can the =
driver
> know? I have no idea. Maybe we can periodically check for such an =
event
> and call igb_refresh_mbufs().
>=20
> Does this make sense to you?
>=20
> Best regards
> Michael
>=20
>=20
> On Feb 9, 2011, at 8:32 AM, Jack Vogel wrote:
>=20
> > Hmmm, well so much for that theory :)
> >
> > Jack
> >
> >
> > On Tue, Feb 8, 2011 at 4:06 PM, Karim Fodil-Lemelin =
<fodillemlinkarim@gmail.com> wrote:
> >
> >
> > 2011/2/8 Jack Vogel <jfvogel@gmail.com>
> >
> >
> > I have been following this, and thinking about it. I still am =
working from a theoretical
> > standpoint, but based on a patch I got quite a long time back and =
never quite groked,
> > I believe now that I might have a solution.
> >
> > The original PR and patch was kern/150516 from Beezar Liu, I was =
never quite comfortable
> > with the code changes, nor convinced that it was a real issue and =
not a misunderstanding.
> > However I think now that this very report might be behind what we =
are seeing today. I have
> > a slightly different approach to solving it, of course it remains to =
be seen if it handles it
> > properly.
> >
> > Please try the patch I've attached, I'm open to further correction =
or polishing of the
> > changes. And thanks to Beezar for his original report and changes, =
this is not for em,
> > but if this eliminates the problem its clearly needed in all =
drivers.
> >
> > Jack
> >
> >
> > Hi Jack,
> >
> > Thanks for your help. I tried your patch and it didn't work so I =
added a couple of printf to see if the added code was getting hit:
> >
> > --- a/freebsd/sys/dev/e1000/if_igb.c
> > --More--(byte 1253)+++ b/freebsd/sys/dev/e1000/if_igb.c
> > @@ -612,7 +612,7 @@ igb_attach(device_t dev)
> > device_get_nameunit(dev));
> >
> > INIT_DEBUGOUT("igb_attach: end");
> > -
> > + printf("this driver has a patch from Jack Vogel\n");
> > return (0);
> >
> > err_late:
> > @@ -4131,6 +4131,7 @@ igb_rxeof(struct igb_queue *que, int count, =
int *done)
> > struct mbuf *sendmp, *mh, *mp;
> > struct igb_rx_buf *rxbuf;
> > u16 hlen, plen, hdr, vtag;
> > + int commit;
> > bool eop =3D FALSE;
> >
> > cur =3D &rxr->rx_base[i];
> > @@ -4255,10 +4256,23 @@ next_desc:
> > bus_dmamap_sync(rxr->rxdma.dma_tag, =
rxr->rxdma.dma_map,
> > BUS_DMASYNC_PREREAD | BUS_DMASYNC_PREWRITE);
> >
> > + commit =3D i; /* capture the old index */
> > +
> > /* Advance our pointers to the next descriptor. */
> > if (++i =3D=3D adapter->num_rx_desc)
> > i =3D 0;
> > /*
> > + ** Sanity test for ring full, if this
> > + ** happens we need to refresh immediately
> > + ** or refresh may deadlock.
> > + */
> > + if (i =3D=3D rxr->next_to_refresh) {
> > + igb_refresh_mbufs(rxr, commit);
> > + printf("igb_refresh_mbufs called with commit =
%d\n", commit);
> > + processed =3D 0;
> > + }
> > +
> > + /*
> > ** Send to the stack or LRO
> > */
> > if (sendmp !=3D NULL) {
> >
> > Here is the results:
> >
> > # dmesg | grep Vogel
> > this driver has a patch from Jack Vogel
> > this driver has a patch from Jack Vogel
> >
> > # netstat -m
> > 60453/52707/113160 mbufs in use (current/cache/total)
> > 48416/51584/100000/100000 mbuf clusters in use =
(current/cache/total/max)
> > 2894/690 mbuf+clusters out of packet secondary zone in use =
(current/cache)
> > 11946/854/12800/12800 4k (page size) jumbo clusters in use =
(current/cache/total/max)
> > 0/0/0/6400 9k jumbo clusters in use (current/cache/total/max)
> > 0/0/0/3200 16k jumbo clusters in use (current/cache/total/max)
> > 164834K/119760K/284595K bytes allocated to network =
(current/cache/total)
> > 0/339/0 requests for mbufs denied (mbufs/clusters/mbuf+clusters)
> > 0/0/0 requests for jumbo clusters denied (4k/9k/16k)
> > 0/4/6656 sfbufs in use (current/peak/max)
> > 0 requests for sfbufs denied
> > 0 requests for sfbufs delayed
> > 0 requests for I/O initiated by sendfile
> > 0 calls to protocol drain routines
> > # dmesg | grep commit
> >
> > At this point RX has hung.
> >
> > Somehow the check (i =3D=3D rxr->next_to_refresh) is never true in =
this case. Also, I did read kern/150516 and couldn't wrap my head around =
the patch for the em driver that Beezar Liu suggested.
> >
> > Regards,
> >
> > Karim.
> >
> >
>=20
>=20
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