[Dovecot] dovecot and nfs readdir vs readdirplus operations

Angel L. Mateo amateo at um.es
Thu Jul 5 15:55:15 EEST 2012

El 04/07/12 23:55, Timo Sirainen escribió:
> On 4.7.2012, at 21.49, Angel L. Mateo wrote:
>> 	Although nfs configuration is the same, there are a lot of differences on readdir vs readdirplus nfs operations. In fact, in the old one we have 12% readdir operations and 3% of readdirplus. And in the new one we have 46% of readdirplus and no readdir operations.
> I'm not entirely sure, but I think it's the kernel that decides if readdir or readdirplus is used and Dovecot can't affect that decision. (Unless maybe kernel does some heuristics.)
	I think you are right. I guess that the differnce between my old system 
(who uses readdir and readdirplus) and the new one (which just uses 
readdirplus) is because of changes on the kernel. For some threads I 
have read (for example, 
http://www.spinics.net/lists/linux-nfs/msg19957.html) it seems that from 
some version in kernel source (2.6.36 if I remmeber well) some nfs 
improvements related with readdir and readdirplus (that makes nfs client 
only uses readdirplus when it was better) and recents kernels always use 

	Concluding... in my systems, with users with hugh mail folders 
(thousands of mails) in maildir format, disabling rdirplus with mount 
options (mount option nordirplus) increases performance (maybe we could 
do more precise test and this could be documented in dovecot's nfs 

Angel L. Mateo Martínez
Sección de Telemática
Área de Tecnologías de la Información
y las Comunicaciones Aplicadas (ATICA)
Tfo: 868887590
Fax: 868888337

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