Date: Fri, 21 Aug 1998 13:48:21 +0200 (CEST) From: Remy NONNENMACHER <remy@synx.com> To: didier@omnix.net Cc: hackers@FreeBSD.ORG, support@yard.de Subject: Re: Yard/FreeBSD problem (fwd) Message-ID: <199808211148.MAA18508@bsd.synx.com> In-Reply-To: <Pine.BSF.3.96.980821114024.4540A-100000@omnix.net>
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On 21 Aug, Didier Derny wrote:
Didier,
In an unmodified kernel (prior to sysctlized delayed_ack), the delayed
ack is always turned ON and the 101-207 bytes problem exists.
TCP_NODELAY option helps the following way :
case TCP_NODELAY OFF :
T Application TCP-client TCP-server DBMS
0 write(...., 150) ---> packet(100) ---> packet(100) --> read()=100
|
(delay 200ms)
|
ack <--- ack
|
packet(50) ---> packet(50) --> read()=50
|
X read()=<n> <---- packet(n) <--- packet(n)+ack <-- DB-reply(n)
in the case, X= 200ms + epsilon (epsilon = neglected net+DBMS+internal
processing time).
case TCP_NODELAY ON :
T Application TCP-client TCP-server DBMS
0 write(...., 150) ---> packet(100) ---> packet(100) --> read()=100
packet(50) ---> packet(50) --> read()=50
|
X read()=<n> <---- packet(n) <--- packet(n)+ack <-- DB-reply(n)
Now, X=0 + epsilon = epsilon.
If you still have the problem, we can be almost sure that TCP_NODELAY
*is* OFF on one or either side. (I don't remember having been said that
it must be ON on *either* side, BTW).
Having the 101-207 bytes problem resolved needs a kernel modification
and a great ancient aprobatur. If nobody takes on it, i offer to (as i
run on it very often and it tires me). Anyway, this doesn't match your
requirement of running with an old kernel version.
Yard told you that they checked this TCP_NODELAY option against
inheritence reseting. If a last chance Yard's code review doesn't
reveal a problem (accepte()d, fork()ed, etc....), I offer to analyse
two tcpdump trace of the same session: one from you and one took on the
machine at Yard, then review kernel codes of the two FreeBSD versions
you (and yard) use.
(Note to Yard: thanks for supporting FreeBSD).
RN.
> Hi,
>
> I still have many problems with Yard/FreeBSD.
>
> I sent my programs / database to Yard last wednesday.
> they did some testing on their version (FreeBSD 2.1.6)
> It worked really fine except for a few slow down.
>
> (for him 350 seconds on a pentium 133)
>
> For me on 3.0-980594-SNAP and FreeBSD-2.2.5-STABLE
> it's still unusable (I stopped the program after
> 25 minutes on a Pentium II 333).
>
> We are writing some application that we are planning to
> bundle with the Yard SQL engine.
>
> I can't imagine that I would have to tell my clients that
> to run our applications they have to install the FreeBSD
> source code and modify the kernel and rebuild it.
>
> do you have any idea on how we could definitively solve this
> problem for 2.2.X and 3.X versions of FreeBSD ?
>
> --
> Didier Derny
> didier@omnix.net
>
>
>
> ---------- Forwarded message ----------
>
> I ran your program on our system and it shows a similar behaviour as you
> describe. Below is the vmstat output, which indicates the hanging moments with
> an idle time of > 50%. But these moments don't seem to be that awful.
> In total your program took 350 seconds on a 133 MHz Pentium.
>
> If the reason for this behaviour is in fact the 100 byte problem mentioned by
> one the FreeBSD guys, the only possible way to solve it would be to
> set ack_delayed=1 (in the kernel?). Anything we at YARD can do?
>
> Regards
>
> Thomas Schonhoven
>
> PS.: I'll be back in office on Friday.
>
>
> $ vmstat 2 200
> procs memory page disks faults cpu
> r b w avm fre flt re pi po fr sr s0 s1 c0 f0 in sy cs us sy id
> 3 0 0 79484 34224 9 1 0 0 6 0 2 0 0 0 233 54 13 1 0 98
> 2 0 0 83792 34088 19 9 0 0 0 0 21 0 0 0 350 4815 1618 66 29 5
> 1 0 0 83956 33924 21 4 0 0 0 0 3 0 0 0 341 5120 1736 67 31 1
> 2 0 0 84096 33772 22 18 0 0 0 0 3 0 0 0 333 4983 1686 72 26 2
> ......
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