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
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20190321204823.GJ9434@mit.edu \
--to=tytso@mit.edu \
--cc=darrick.wong@oracle.com \
--cc=lczerner@redhat.com \
--cc=linux-ext4@vger.kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.