From: David Howells <dhowells@redhat.com>
To: Miklos Szeredi <miklos@szeredi.hu>
Cc: dhowells@redhat.com, Ian Kent <raven@themaw.net>,
Linus Torvalds <torvalds@linux-foundation.org>,
Al Viro <viro@zeniv.linux.org.uk>,
Linux NFS list <linux-nfs@vger.kernel.org>,
Andreas Dilger <adilger.kernel@dilger.ca>,
Anna Schumaker <anna.schumaker@netapp.com>,
"Theodore Ts'o" <tytso@mit.edu>,
Linux API <linux-api@vger.kernel.org>,
linux-ext4@vger.kernel.org,
Trond Myklebust <trond.myklebust@hammerspace.com>,
Miklos Szeredi <mszeredi@redhat.com>,
Christian Brauner <christian@brauner.io>,
Jann Horn <jannh@google.com>,
"Darrick J. Wong" <darrick.wong@oracle.com>,
Karel Zak <kzak@redhat.com>, Jeff Layton <jlayton@redhat.com>,
linux-fsdevel@vger.kernel.org,
LSM <linux-security-module@vger.kernel.org>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 00/13] VFS: Filesystem information [ver #19]
Date: Wed, 01 Apr 2020 16:51:43 +0100 [thread overview]
Message-ID: <2583800.1585756303@warthog.procyon.org.uk> (raw)
In-Reply-To: <CAJfpeguxACC68bMhS-mNm4m6ytrKgs1--jbF5X3tBiPf_iG1jg@mail.gmail.com>
Miklos Szeredi <miklos@szeredi.hu> wrote:
> For 30000 mounts, f= 146400us f2= 136766us p= 1406569us p2=
> 221669us; p=9.6*f p=10.3*f2 p=6.3*p2
f = 146400us
f2= 136766us
p = 1406569us <--- Order of magnitude slower
p2= 221669us
And more memory used because it's added a whole bunch of inodes and dentries
to the cache. For each mount that's a pair for each dir and a pair for each
file within the dir. So for the two files my test is reading, for 30000
mounts, that's 90000 dentries and 90000 inodes in mountfs alone.
(gdb) p sizeof(struct dentry)
$1 = 216
(gdb) p sizeof(struct inode)
$2 = 696
(gdb) p (216*696)*30000*3/1024/1024
$3 = 615
so 615 MiB of RAM added to the caches in an extreme case.
We're seeing customers with 10000+ mounts - that would be 205 MiB, just to
read two values from each mount.
I presume you're not going through /proc/fdinfo each time as that would add
another d+i - for >1GiB added to the caches for 30000 mounts.
David
next prev parent reply other threads:[~2020-04-01 15:51 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-18 15:08 [PATCH 00/13] VFS: Filesystem information [ver #19] David Howells
2020-03-18 15:08 ` [PATCH 01/13] fsinfo: Add fsinfo() syscall to query filesystem " David Howells
2020-03-18 15:08 ` [PATCH 02/13] fsinfo: Provide a bitmap of supported features " David Howells
2020-03-18 15:08 ` [PATCH 03/13] fsinfo: Allow retrieval of superblock devname, options and stats " David Howells
2020-03-18 15:08 ` [PATCH 04/13] fsinfo: Allow fsinfo() to look up a mount object by ID " David Howells
2020-03-18 15:08 ` [PATCH 05/13] fsinfo: Add a uniquifier ID to struct mount " David Howells
2020-03-18 15:09 ` [PATCH 06/13] fsinfo: Allow mount information to be queried " David Howells
2020-03-18 15:09 ` [PATCH 07/13] fsinfo: Allow mount topology and propagation info to be retrieved " David Howells
2020-03-18 15:09 ` [PATCH 08/13] fsinfo: Provide notification overrun handling support " David Howells
2020-03-18 15:09 ` [PATCH 09/13] fsinfo: sample: Mount listing program " David Howells
2020-03-18 15:09 ` [PATCH 10/13] fsinfo: Add API documentation " David Howells
2020-03-18 15:09 ` [PATCH 11/13] fsinfo: Add support for AFS " David Howells
2020-03-18 15:09 ` [PATCH 12/13] fsinfo: Example support for Ext4 " David Howells
2020-03-18 15:10 ` [PATCH 13/13] fsinfo: Example support for NFS " David Howells
2020-03-18 16:05 ` [PATCH 00/13] VFS: Filesystem information " Miklos Szeredi
2020-04-01 5:22 ` Ian Kent
2020-04-01 8:18 ` Miklos Szeredi
2020-04-01 8:27 ` David Howells
2020-04-01 8:37 ` Miklos Szeredi
2020-04-01 12:35 ` Miklos Szeredi
2020-04-01 15:51 ` David Howells [this message]
2020-04-02 1:38 ` Ian Kent
2020-04-02 14:14 ` Karel Zak
2020-03-19 10:37 ` David Howells
2020-03-19 12:36 ` Miklos Szeredi
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