Date: Fri, 11 Feb 2011 11:57:08 -0800 From: Jack Vogel <jfvogel@gmail.com> To: Karim Fodil-Lemelin <fodillemlinkarim@gmail.com> Cc: freebsd-net@freebsd.org Subject: Re: igb driver RX (was TX) hangs when out of mbuf clusters Message-ID: <AANLkTik2=_Vg92t6qNTNvT-y3OdAQC=MQ40r=OrHER=b@mail.gmail.com> In-Reply-To: <AANLkTinSFycBZx31A-QQoweEVAD-tsEBnuZW5%2BpZgP2Z@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> <12838373-FE96-443E-8979-AF5408705BF0@freebsd.org> <AANLkTinSFycBZx31A-QQoweEVAD-tsEBnuZW5%2BpZgP2Z@mail.gmail.com>
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Yes, it was the fix for this, Mike has tested and confirmed it eliminates
the problem, and yes
I will MFC the relevant bits back to 8 and 7 for you asap.
Jack
On Fri, Feb 11, 2011 at 11:53 AM, Karim Fodil-Lemelin <
fodillemlinkarim@gmail.com> wrote:
> Hi,
>
> I see a commit was made in current (r218530 | jfv | 2011-02-10 20:00:26
> -0500 (Thu, 10 Feb 2011)). Is that commit done to address this issue?
>
> And if so Is there any MFC planned for 7.4 for this?
>
> Thanks,
>
> Karim.
>
> 2011/2/9 Michael Tuexen <tuexen@freebsd.org>
>
> 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).
>> >
>> > 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
>> >
>> > Thanks for your help,
>> >
>> > Jack
>> >
>> >
>> > On Wed, Feb 9, 2011 at 2:36 AM, Michael Tuexen <tuexen@freebsd.org>
>> wrote:
>> > Hi Jack,
>> >
>> > I could recreate the problem. When the problem occurs, we see
>> >
>> > rx_nxt_check = n
>> > rx_nxt_refresh = n + 1
>> >
>> > (This was also reported in a mail from Karim)
>> >
>> > This means that the *whole* receive ring has no buffers anymore. This
>> can
>> > occur if, for some amount of time, no clusters are available.
>> >
>> > 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().
>> >
>> > Does this make sense to you?
>> >
>> > Best regards
>> > Michael
>> >
>> >
>> > On Feb 9, 2011, at 8:32 AM, Jack Vogel wrote:
>> >
>> > > 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 = FALSE;
>> > >
>> > > cur = &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 = i; /* capture the old index */
>> > > +
>> > > /* Advance our pointers to the next descriptor. */
>> > > if (++i == adapter->num_rx_desc)
>> > > i = 0;
>> > > /*
>> > > + ** Sanity test for ring full, if this
>> > > + ** happens we need to refresh immediately
>> > > + ** or refresh may deadlock.
>> > > + */
>> > > + if (i == rxr->next_to_refresh) {
>> > > + igb_refresh_mbufs(rxr, commit);
>> > > + printf("igb_refresh_mbufs called with commit
>> %d\n", commit);
>> > > + processed = 0;
>> > > + }
>> > > +
>> > > + /*
>> > > ** Send to the stack or LRO
>> > > */
>> > > if (sendmp != 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 == 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.
>> > >
>> > >
>> >
>> >
>>
>>
>
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