The -l flag is causing a metadata lookup for every file in the directory. The
way the ls command does that it's with individual fstat calls to each directory
entry. That's a lot of tiny network round trips with fops that don't even fill
a standard frame thus each frame has a high percentage of overhead for tcp. Add
to that the replica check to ensure you're not getting stale data and you have
another round trip for each file. Your 123k directory entries require several
frames of getdirent and over 492k frames for the individual fstat calls. That's
roughly 16us per frame.
Can you eliminate the fstat calls? If you only get the directory listing that
should be significantly better. To prove this, do "echo *". You will instantly
see your 123k entries.
On November 27, 2017 5:18:56 AM PST, Aaron Roberts <[email protected]>
wrote:
>Hi,
>I have a situation where an apache web server is trying to locate the
>IndexDocument for a directory on a gluster volume. This URL is being
>hit roughly 20 times per second. There is only 1 file in this
>directory. However, the parent directory does have a large number of
>items (+123,000 files and dirs) and we are performing operations to
>move these files into 2 levels of subdirs.
>
>We are seeing very slow response times (around 8 seconds) in apache and
>also when trying to ls on this dir. Before we started the migrations
>to move files on the large parent dir into 2 sub levels, we weren't
>aware of a problem.
>
>[root@web-02 images]# time ls -l dir1/get/ | wc -l
>2
>
>real 0m8.114s
>user 0m0.002s
>sys 0m0.014s
>
>Other directories with only 1 item return very quickly (<1 sec).
>
>[root@Web-01 images]# time ls -l dir1/tmp1/ | wc -l
>2
>
>real 0m0.014s
>user 0m0.003s
>sys 0m0.006s
>
>I'm just trying to understand what would slow down this operation so
>much. Is it the high frequency of attempts to read the directory
>(apache hits to dir1/get/) ? Do the move operations on items in the
>parent directory have any impact?
>
>Some background info:
>
>[root@web-02 images]# gluster --version
>glusterfs 3.7.20 built on Jan 30 2017 15:39:29
>Repository revision: git://git.gluster.com/glusterfs.git
>Copyright (c) 2006-2011 Gluster Inc. <http://www.gluster.com>
>GlusterFS comes with ABSOLUTELY NO WARRANTY.
>You may redistribute copies of GlusterFS under the terms of the GNU
>General Public License.
>
>[root@web-02 images]# gluster vol info
>
>Volume Name: web_vol1
>Type: Replicate
>Volume ID: 0d63de20-c9c2-4931-b4a3-6aed5ae28057
>Status: Started
>Number of Bricks: 1 x 2 = 2
>Transport-type: tcp
>Bricks:
>Brick1: web-01:/export/brick1/web_vol1_brick1
>Brick2: web-02:/export/brick1/web_vol1_brick1
>Options Reconfigured:
>performance.readdir-ahead: on
>performance.io-thread-count: 32
>performance.cache-size: 512MB
>
>
>Any insight would be gratefully received.
>
>Thanks,
> Aaron
--
Sent from my Android device with K-9 Mail. Please excuse my brevity.
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