Re: Differences between 2.6.5 und 2.6.16: getattr with actimeo=0 and O_DIRECT

[Gerd Bavendiek <gerd.bavendiek@googlemail.com>]

Trond Myklebust schrieb:
> On Tue, 2007-11-13 at 10:03 +0100, Gerd Bavendiek wrote:
>> Hi,
>>
>> analyzing performance issues with Oracle databases on an NFS client
>> running on SLES9 SP3 and NetApp as NFS server, I found that in SLES9
>> SP3 each write call is followed by an getattr. This is not the case
>> with SLES10 SP1.
>>
>> Mount options in use are:
>>
>> rw,v3,rsize=32768,wsize=32768,acregmin=0,acregmax=0,acdirmin=0,acdirmax=0,hard,lock,proto=tcp,addr=172.18.131.134
>>
>> I do
>>
>> dd if=/dev/zero of=/mnt/qqq oflag=direct bs=8k count=100000
>>
>> and using tcpdump (BTW, is there an easier way ?) I see with SLES9 SP3
>> (i.e. 2.6.5-7.244) each single 8k write followed by an getattr (which
>> comes at some cost).
>>
>> Using SLES10 SP1 (2.6.16.46-0.12) there is only one getattr when dd
>> closes the file.
>>
>> Is there anything I can do to avoid the getattr calls in SLES9 SP3
>> (no, sorry, can't update to SLES10 SP1) ?
> 
> For one thing, you could turn attribute caching back on. I don't know
> why SLES10 fails to GETATTR, but acregmin=0,acregmax=0 turns attribute
> caching off. Append writes need to know where the end-of-file is, and so
> they will force a GETATTR when there is no attribute caching.
> 
> Trond
> 
> 

Trond,

you say: SLES10 fails to GETATTR.

So with acregmin=0,acregmax=0 etc. we should always have one write AND 
one getattr ?

So SLES9 SP3 does it the right way ?

Gerd

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