From: Trond Myklebust <trondmy@hammerspace.com>
To: "tigran.mkrtchyan@desy.de" <tigran.mkrtchyan@desy.de>,
"linux-nfs@vger.kernel.org" <linux-nfs@vger.kernel.org>
Subject: Re: readdir request re-requests entries
Date: Sat, 20 Oct 2018 18:22:07 +0000 [thread overview]
Message-ID: <f9f24f44266292dc5fa41f633344b11cf84cc4f8.camel@hammerspace.com> (raw)
In-Reply-To: <174380207.12564567.1539987095714.JavaMail.zimbra@desy.de>
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WARNING: multiple messages have this Message-ID (diff)
From: Trond Myklebust <trondmy@hammerspace.com>
To: "tigran.mkrtchyan@desy.de" <tigran.mkrtchyan@desy.de>,
"linux-nfs@vger.kernel.org" <linux-nfs@vger.kernel.org>
Subject: Re: readdir request re-requests entries
Date: Sat, 20 Oct 2018 18:22:07 +0000 [thread overview]
Message-ID: <f9f24f44266292dc5fa41f633344b11cf84cc4f8.camel@hammerspace.com> (raw)
Message-ID: <20181020182207.QvfxEttc6zzbvvulpHM8sj33TW29FqfyDxZ4DLcimKo@z> (raw)
In-Reply-To: <174380207.12564567.1539987095714.JavaMail.zimbra@desy.de>
On Sat, 2018-10-20 at 00:11 +0200, Mkrtchyan, Tigran wrote:
> Dear NFS fellows,
>
> we have notice a behavior of nfs client when iterating over a big
> directory. The client re-requests entries that already has been. For
> example, a client issues READDIR on a directory with 1k files.
> Initial cookie
> is 0, maxcount 32768.
>
> c -> s cookie 0
> s -> c last cookie 159
> c -> s cookie 105
> s -> c last cookie 259
> c -> s cookie 207
>
> ...
>
> and so on. The interesting thing is, if I mount with rsize 8192
> (maxcount 8192), then first couple
> or requests are asking for correct cookies - 0, 43, 81, 105. Again
> 105 as with maxcount 32678. To
> me it looks like that there is some kind of internal page (actually
> NFS_MAX_READDIR_PAGES) alignment
> and entries which do not fit into initially allocated PAGE_SIZE *
> NFS_MAX_READDIR_PAGES memory
> just get dropped.
>
> As 30% of each reply is thrown away, listing of large directories may
> produce much more requests
> than required.
>
> Is it an expected behavior?
Yes.
--
Trond Myklebust
Linux NFS client maintainer, Hammerspace
trond.myklebust@hammerspace.com
next prev parent reply other threads:[~2018-10-21 2:33 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-10-19 22:11 readdir request re-requests entries Mkrtchyan, Tigran
2018-10-20 18:22 ` Trond Myklebust [this message]
2018-10-20 18:22 ` Trond Myklebust
2018-10-20 18:57 ` Frank Sorenson
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