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Date:      Tue, 2 Mar 2010 19:52:40 -0500 (EST)
From:      Rick Macklem <rmacklem@uoguelph.ca>
To:        Daniel Braniss <danny@cs.huji.ac.il>
Cc:        stable@freebsd.org, freebsd-fs@freebsd.org, Willem Jan Withagen <wjw@digiware.nl>, =?utf-8?B?RWlyaWsgw5h2ZXJieQ==?= <ltning@anduin.net>, rwatson@freebsd.org, Jeremy Chadwick <freebsd@jdc.parodius.com>
Subject:   Re: mbuf leakage with nfs/zfs? 
Message-ID:  <Pine.GSO.4.63.1003021947470.3879@muncher.cs.uoguelph.ca>
In-Reply-To: <E1NmPHy-0009jy-Dj@kabab.cs.huji.ac.il>
References:  <20100226174021.8feadad9.gerrit@pmp.uni-hannover.de>  <E1Nl6VA-000557-D9@kabab.cs.huji.ac.il> <20100226224320.8c4259bf.gerrit@pmp.uni-hannover.de> <4B884757.9040001@digiware.nl> <20100227080220.ac6a2e4d.gerrit@pmp.uni-hannover.de> <4B892918.4080701@digiware.nl> <20100227202105.f31cbef7.gerrit@pmp.uni-hannover.de> <20100227193819.GA60576@icarus.home.lan> <BD8AC9F6-DF96-41F9-8E92-48A4E5606DC7@anduin.net> <4B89943C.70704@digiware.nl> <20100227220310.GA65110@icarus.home.lan> <Pine.GSO.4.63.1003011703100.26054@muncher.cs.uoguelph.ca> <E1NmPHy-0009jy-Dj@kabab.cs.huji.ac.il>

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On Tue, 2 Mar 2010, Daniel Braniss wrote:

> runing with the experimental nfs server all is ok!
> (at least I can't see any mbuf leakage :-)
>
> so now that we can  assume that the problem is in NFS/UDP writes via
> classic nfsserver, where to look?
>

It might also be the krpc reply cache, since the experimental server
isn't using it (nfsv4 requires a rather twisted reply cache and it was
easier to just use that one for nfsv2,3 for the experimental server,
as well).

>> If it doesn't go away, the problem is more likely in the krpc or the
>> generic udp code. (When I looked at svc_dg.c, I could only spot one
>> possible leak and you've already determined that patch doesn't help.
>> The other big difference when using udp on the FreeBSD8 krpc is the
>> reply cache code. I seem to recall it's an lru cache with a fixed upper
>> bound, but it might be broken and leaking.
>>
>> If you change the server to set sp_rcache = NULL in the initialization
>> function in sys/nfsserver/nfs_srvkrpc.c, I think that disables the replay
>> cache. You wouldn't want to run this way in production, but it would
>> determine if the leak is in it.
>>
>> Change the 3 lines in nfsrv_init() to:
>> nfsrv_pool->sp_rcache = NULL;
>> nfsrv_pool->sp_assign = NULL;
>> nfsrv_pool->sp_done = NULL;
>>
>> and I think the krpc replay cache will be disabled.
>>

If someone gets a chance to try the above (not in production mode:-),
it will determine if the problem is in the reply cache or the nfs server's
write code.
>> Good luck with it and please report back if you get to try the above.
>>

Thanks for trying the experimental server. It is getting narrowed down,
due to everyone's work on it.

rick




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