Date: Mon, 3 Jul 1995 09:52:46 +0300 From: Heikki Suonsivu <hsu@clinet.fi> To: freebsd-current@freefall.cdrom.com Subject: Re: kern/579: sio: RS_IBUFSIZE 256 too small Message-ID: <199507030652.JAA00240@katiska.clinet.fi>
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In article <199507021921.TAA26200@puffin.pelican.com> Pete Carah <pete@puffin.pelican.com> writes:
>> Both these machines report "interrupt-level buffer overflow":s
>> very frequently on a leased line running at 38400, badly dropping
...
>This is because you don't use crtscts and something or other delays
On many async leased lines there is no hardware flow control, all you get
through is two data wires. Even if there was, if you stop receiving
because internal rs buffer overflows, you are idling the fixed-speed link,
thus it should only done if the machine really can't cope with all the data
(but it certainly does cope in this case). After pushing the input buffer
to 4k I got a significant performance improvement and no more loss of data.
My workaround is apparently wrong, it works as I don't need and don't have
rts/cts flow control, but clearly something needs to be done to sio in this
respect. 256 bytes seems overly tight to me, moving data in pieces this
small is waste of cpu. Does it need to do a context switch or interrupt
for each time it loads the 256 byte buffer to a tty buffer?
>> On 386-16 I also saw several spontaneous reboots when loading the
>> PPP link.
Is this the old route delete bug? Must be independent of ttyhog and such.
I have seen a few bpf commits recently to deal with tcpdump on down interfaces.
Don't know if they fix anything since I don't use bpf particularly.
I have bpf enabled in kernel but I haven't used tcpdump on the interface
(at the time it reboots). The kernels are recent (2.0.5R and up).
--
Heikki Suonsivu, T{ysikuu 10 C 83/02210 Espoo/FINLAND,
hsu@cs.hut.fi home +358-0-8031121 work -4513377 fax -4555276 riippu SN
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