From: "Theodore Ts'o" <tytso@mit.edu>
To: Lukas Czerner <lczerner@redhat.com>
Cc: Ext4 Developers List <linux-ext4@vger.kernel.org>,
darrick.wong@oracle.com
Subject: Re: [PATCH 8/9] e2scrub_all: refactor device probe loop
Date: Thu, 21 Mar 2019 16:48:23 -0400 [thread overview]
Message-ID: <20190321204823.GJ9434@mit.edu> (raw)
In-Reply-To: <20190321201710.vw5g2kfp6p2b3jxk@work>
On Thu, Mar 21, 2019 at 09:17:10PM +0100, Lukas Czerner wrote:
>
> Right, I did mention it later in the reply. It can be filtered
>
> grep -v '^/dev/'
Well, that assumes all device nodes are in /dev. Which is not
necessarily always the case, especially in some of the more _whacky_
container setups which I've seen. (Hmm, is whacky redundant here?)
I suppose can test whether or not the path is a block device or a
directory.....
>
> For me this new function is the wors of all.
>
> cold cache:
> real 0m2.115s
> user 0m0.040s
> sys 0m0.154s
>
> second time:
> real 0m1.100s
> user 0m0.037s
> sys 0m0.122s
>
> But that's because of blkid which is terribly slow for some reason.
I ran my test on a system with a NVMe SSD, and no HDD's attached. I
just did an strace, and I see the util-linux folks have really done a
great job of pessimizing blkid. :-(
My version used to just pull the information from the blkid cache file
and then verified the results, but it looks like the new, improved
util-linux version of blkid scans the /dev directory and opens and
reads from each device node, even when we're querying a single block
device. <groan>
Even lsblk is *amazingly* inefficient in terms of the number of
useless file opens which it performs, although at least they are all
/sysfs files.
I'm half tempted to create and ship a binary which just calls
ext2fs_check_mount_point() and returns the value, since it's the most
efficient. This command
sudo strace -o /tmp/st /build/e2fsprogs-maint/lib/ext2fs/tst_ismounted /dev/lambda/tp
Opens /proc/mounts and does a trial mount of /dev/lambda/tp to make
sure it's actually busy, and that's it.
Sigh...
- Ted
next prev parent reply other threads:[~2019-03-21 20:48 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-21 2:02 [PATCH 1/9] e2scrub: check to make sure lvm2 is installed Theodore Ts'o
2019-03-21 2:02 ` [PATCH 2/9] debian: drop lvm2 from the recommends line Theodore Ts'o
2019-03-21 3:57 ` Darrick J. Wong
2019-03-21 2:02 ` [PATCH 3/9] Fix "make install-strip" Theodore Ts'o
2019-03-21 2:02 ` [PATCH 4/9] e2scrub: fix up "make install-strip" support Theodore Ts'o
2019-03-21 2:02 ` [PATCH 5/9] e2fscrub: add the -n option which shows what commands e2scrub would execute Theodore Ts'o
2019-03-21 3:59 ` Darrick J. Wong
2019-03-21 10:57 ` Lukas Czerner
2019-03-21 14:32 ` Theodore Ts'o
2019-03-21 2:02 ` [PATCH 6/9] e2scrub_all: add the -n option which shows what e2scrub_all would do Theodore Ts'o
2019-03-21 4:01 ` Darrick J. Wong
2019-03-21 2:02 ` [PATCH 7/9] e2scrub_all: make sure there's enough free space for a snapshot Theodore Ts'o
2019-03-21 4:02 ` Darrick J. Wong
2019-03-21 11:18 ` Lukas Czerner
2019-03-21 14:26 ` Theodore Ts'o
2019-03-21 2:02 ` [PATCH 8/9] e2scrub_all: refactor device probe loop Theodore Ts'o
2019-03-21 4:05 ` Darrick J. Wong
2019-03-21 10:27 ` Lukas Czerner
2019-03-21 14:31 ` Theodore Ts'o
2019-03-21 15:57 ` Lukas Czerner
2019-03-21 18:24 ` Theodore Ts'o
2019-03-21 20:17 ` Lukas Czerner
2019-03-21 20:48 ` Theodore Ts'o [this message]
2019-03-21 21:14 ` Lukas Czerner
2019-03-21 22:04 ` Theodore Ts'o
2019-03-21 22:08 ` Theodore Ts'o
2019-03-22 9:38 ` Lukas Czerner
2019-03-21 20:09 ` Andreas Dilger
2019-03-21 17:48 ` Theodore Ts'o
2019-03-21 19:49 ` Lukas Czerner
2019-03-21 20:23 ` Theodore Ts'o
2019-03-21 16:10 ` Lukas Czerner
2019-03-21 2:02 ` [PATCH 9/9] e2scrub,e2scrub_all: print a (more understandable) error if not run as root Theodore Ts'o
2019-03-21 4:04 ` Darrick J. Wong
2019-03-21 11:36 ` Lukas Czerner
2019-03-21 14:40 ` Theodore Ts'o
2019-03-21 3:55 ` [PATCH 1/9] e2scrub: check to make sure lvm2 is installed Darrick J. Wong
-- strict thread matches above, loose matches on Subject: below --
2019-03-21 20:25 [PATCH -v2 0/9] e2fsprogs: e2scrub cleanups Theodore Ts'o
2019-03-21 20:25 ` [PATCH 8/9] e2scrub_all: refactor device probe loop Theodore Ts'o
2019-03-21 20:55 ` Lukas Czerner
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