Date: Fri, 5 Dec 2014 09:14:26 -0500 (EST) From: Rick Macklem <rmacklem@uoguelph.ca> To: =?utf-8?B?TG/Dr2M=?= Blot <loic.blot@unix-experience.fr> Cc: freebsd-fs@freebsd.org Subject: Re: High Kernel Load with nfsv4 Message-ID: <581583623.5730217.1417788866930.JavaMail.root@uoguelph.ca> In-Reply-To: <f17b01856a1a37c5ac830ae7490f2624@mail.unix-experience.fr>
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Loic Blot wrote: > Hi, > i'm trying to create a virtualisation environment based on jails. > Those jails are stored under a big ZFS pool on a FreeBSD 9.3 which > export a NFSv4 volume. This NFSv4 volume was mounted on a big > hypervisor (2 Xeon E5v3 + 128GB memory and 8 ports (but only 1 was > used at this time). > > The problem is simple, my hypervisors runs 6 jails (used 1% cpu and > 10GB RAM approximatively and less than 1MB bandwidth) and works > fine at start but the system slows down and after 2-3 days become > unusable. When i look at top command i see 80-100% on system and > commands are very very slow. Many process are tagged with nfs_cl*. > To be honest, I would expect the slowness to be because of slow response from the NFSv4 server, but if you do: # ps axHl on a client when it is slow and post that, it would give us some more information on where the client side processes are sitting. If you also do something like: # nfsstat -c -w 1 and let it run for a while, that should show you how many RPCs are being done and which ones. # nfsstat -m will show you what your mount is actually using. The only mount option I can suggest trying is "rsize=32768,wsize=32768", since some network environments have difficulties with 64K. There are a few things you can try on the NFSv4 server side, if it appears that the clients are generating a large RPC load. - disabling the DRC cache for TCP by setting vfs.nfsd.cachetcp=0 - If the server is seeing a large write RPC load, then "sync=disabled" might help, although it does run a risk of data loss when the server crashes. Then there are a couple of other ZFS related things (I'm not a ZFS guy, but these have shown up on the mailing lists). - make sure your volumes are 4K aligned and ashift=12 (in case a drive that uses 4K sectors is pretending to be 512byte sectored) - never run over 70-80% full if write performance is an issue - use a zil on an SSD with good write performance The only NFSv4 thing I can tell you is that it is known that ZFS's algorithm for determining sequential vs random I/O fails for NFSv4 during writing and this can be a performance hit. The only workaround is to use NFSv3 mounts, since file handle affinity apparently fixes the problem and this is only done for NFSv3. rick > I saw that there are TSO issues with igb then i'm trying to disable > it with sysctl but the situation wasn't solved. > > Someone has got ideas ? I can give you more informations if you > need. > > Thanks in advance. > Regards, > > Loïc Blot, > UNIX Systems, Network and Security Engineer > http://www.unix-experience.fr > _______________________________________________ > freebsd-fs@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-fs > To unsubscribe, send any mail to "freebsd-fs-unsubscribe@freebsd.org"home | help
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