getattr miss

getattr miss

[Benjamin Coddington]

Forgive me for what may be an obvious question.  In the middle of 
tracking down NFS4ERR_RESOURCE storms from an AIX server to linux 
clients on three busy webservers, I noticed that our linux client 
performs a compound OPEN,GETATTR for every read of a file even if the 
reads are well within the attribute cache timeout.  Adding nocto doesn't 
seem to change this behavior -- and for apache looking up numerous 
.htaccess files it would be great to avoid the trip to the server to 
revalidate attributes if we're within the timeout.

So the simple question: is this expected?  I'd like to minimize 
consecutive GETATTR calls, if possible, and get the most from VFS cache.

I've got some ridiculous timeouts set up at this point:

barasinga.uvm.edu:/ on /fs/barasinga type nfs4 
rw,sec=krb5,nocto,hard,intr,actimeo=3600,addr=132.198.101.73

Ben
-- 
Benjamin Coddington
Systems Architecture and Administration
Enterprise Technology Services
University of Vermont

Re: getattr miss

[J. Bruce Fields]

On Tue, Feb 17, 2009 at 03:43:38PM -0500, Benjamin Coddington wrote:
> Forgive me for what may be an obvious question.  In the middle of  
> tracking down NFS4ERR_RESOURCE storms from an AIX server to linux  
> clients on three busy webservers, I noticed that our linux client  
> performs a compound OPEN,GETATTR for every read of a file even if the  
> reads are well within the attribute cache timeout.  Adding nocto doesn't  
> seem to change this behavior -- and for apache looking up numerous  
> .htaccess files it would be great to avoid the trip to the server to  
> revalidate attributes if we're within the timeout.

The NFSv4 client has to send an open to the server on each local open.

The one way to avoid this is with delegations.  I don't know what sort
of delegation support the AIX server has.  Probably at least some.

NFSv4.0 delegations require the server to open a separate connection
back to the client for recalls; a NAT or firewall could be getting in
the way of that.

--b.

>
> So the simple question: is this expected?  I'd like to minimize  
> consecutive GETATTR calls, if possible, and get the most from VFS cache.
>
> I've got some ridiculous timeouts set up at this point:
>
> barasinga.uvm.edu:/ on /fs/barasinga type nfs4  
> rw,sec=krb5,nocto,hard,intr,actimeo=3600,addr=132.198.101.73
>
> Ben
> -- 
> Benjamin Coddington
> Systems Architecture and Administration
> Enterprise Technology Services
> University of Vermont
> --
> To unsubscribe from this list: send the line "unsubscribe linux-nfs" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html

Re: getattr miss

[Benjamin Coddington]

Looks like our AIX server supports read delegations, but they don't seem 
to be used.  NAT/Firewall is not an issue here.  Instead, the AIX server 
always requires OPEN_CONFIRM, and so there are no delegations.  So now 
I'm trying to figure out why every open needs a confirm..  Thanks.

B

J. Bruce Fields wrote:
> On Tue, Feb 17, 2009 at 03:43:38PM -0500, Benjamin Coddington wrote:
>> Forgive me for what may be an obvious question.  In the middle of  
>> tracking down NFS4ERR_RESOURCE storms from an AIX server to linux  
>> clients on three busy webservers, I noticed that our linux client  
>> performs a compound OPEN,GETATTR for every read of a file even if the  
>> reads are well within the attribute cache timeout.  Adding nocto doesn't  
>> seem to change this behavior -- and for apache looking up numerous  
>> .htaccess files it would be great to avoid the trip to the server to  
>> revalidate attributes if we're within the timeout.
> 
> The NFSv4 client has to send an open to the server on each local open.
> 
> The one way to avoid this is with delegations.  I don't know what sort
> of delegation support the AIX server has.  Probably at least some.
> 
> NFSv4.0 delegations require the server to open a separate connection
> back to the client for recalls; a NAT or firewall could be getting in
> the way of that.
> 
> --b.
> 
>> So the simple question: is this expected?  I'd like to minimize  
>> consecutive GETATTR calls, if possible, and get the most from VFS cache.
>>
>> I've got some ridiculous timeouts set up at this point:
>>
>> barasinga.uvm.edu:/ on /fs/barasinga type nfs4  
>> rw,sec=krb5,nocto,hard,intr,actimeo=3600,addr=132.198.101.73
>>
>> Ben
>> -- 
>> Benjamin Coddington
>> Systems Architecture and Administration
>> Enterprise Technology Services
>> University of Vermont
>> --
>> To unsubscribe from this list: send the line "unsubscribe linux-nfs" in
>> the body of a message to majordomo@vger.kernel.org
>> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>