[Gluster-users] Very slow rsync to gluster volume UNLESS `ls` or `find` scan dir on gluster volume first

Tue Feb 27 13:52:16 UTC 2018

Any updates on this one?

On Mon, Feb 5, 2018 at 8:18 AM, Tom Fite <tomfite at gmail.com> wrote:

> Hi all,
>
> I have seen this issue as well, on Gluster 3.12.1. (3 bricks per box, 2
> boxes, distributed-replicate) My testing shows the same thing -- running a
> find on a directory dramatically increases lstat performance. To add
> another clue, the performance degrades again after issuing a call to reset
> the system's cache of dentries and inodes:
>
> # sync; echo 2 > /proc/sys/vm/drop_caches
>
> I think that this shows that it's the system cache that's actually doing
> the heavy lifting here. There are a couple of sysctl tunables that I've
> found helps out with this.
>
> See here:
>
> http://docs.gluster.org/en/latest/Administrator%20Guide/
> Linux%20Kernel%20Tuning/
>
> Contrary to what that doc says, I've found that setting
> vm.vfs_cache_pressure to a low value increases performance by allowing more
> dentries and inodes to be retained in the cache.
>
> # Set the swappiness to avoid swap when possible.
> vm.swappiness = 10
>
> # Set the cache pressure to prefer inode and dentry cache over file cache.
> This is done to keep as many
> # dentries and inodes in cache as possible, which dramatically improves
> gluster small file performance.
> vm.vfs_cache_pressure = 25
>
> For comparison, my config is:
>
> Volume Name: gv0
> Type: Tier
> Volume ID: d490a9ec-f9c8-4f10-a7f3-e1b6d3ced196
> Status: Started
> Snapshot Count: 13
> Number of Bricks: 8
> Transport-type: tcp
> Hot Tier :
> Hot Tier Type : Replicate
> Number of Bricks: 1 x 2 = 2
> Brick1: gluster2:/data/hot_tier/gv0
> Brick2: gluster1:/data/hot_tier/gv0
> Cold Tier:
> Cold Tier Type : Distributed-Replicate
> Number of Bricks: 3 x 2 = 6
> Brick3: gluster1:/data/brick1/gv0
> Brick4: gluster2:/data/brick1/gv0
> Brick5: gluster1:/data/brick2/gv0
> Brick6: gluster2:/data/brick2/gv0
> Brick7: gluster1:/data/brick3/gv0
> Brick8: gluster2:/data/brick3/gv0
> Options Reconfigured:
> performance.cache-max-file-size: 128MB
> cluster.readdir-optimize: on
> cluster.watermark-hi: 95
> features.ctr-sql-db-cachesize: 262144
> cluster.read-freq-threshold: 5
> cluster.write-freq-threshold: 2
> features.record-counters: on
> cluster.tier-promote-frequency: 15000
> cluster.tier-pause: off
> cluster.tier-compact: on
> cluster.tier-mode: cache
> features.ctr-enabled: on
> performance.cache-refresh-timeout: 60
> performance.stat-prefetch: on
> server.outstanding-rpc-limit: 2056
> cluster.lookup-optimize: on
> performance.client-io-threads: off
> nfs.disable: on
> transport.address-family: inet
> features.barrier: disable
> client.event-threads: 4
> server.event-threads: 4
> performance.cache-size: 1GB
> network.inode-lru-limit: 90000
> performance.md-cache-timeout: 600
> performance.cache-invalidation: on
> features.cache-invalidation-timeout: 600
> features.cache-invalidation: on
> performance.quick-read: on
> performance.io-cache: on
> performance.nfs.write-behind-window-size: 4MB
> performance.write-behind-window-size: 4MB
> performance.nfs.io-threads: off
> network.tcp-window-size: 1048576
> performance.rda-cache-limit: 64MB
> performance.flush-behind: on
> server.allow-insecure: on
> cluster.tier-demote-frequency: 18000
> cluster.tier-max-files: 1000000
> cluster.tier-max-promote-file-size: 10485760
> cluster.tier-max-mb: 64000
> features.ctr-sql-db-wal-autocheckpoint: 2500
> cluster.tier-hot-compact-frequency: 86400
> cluster.tier-cold-compact-frequency: 86400
> performance.readdir-ahead: off
> cluster.watermark-low: 50
> storage.build-pgfid: on
> performance.rda-request-size: 128KB
> performance.rda-low-wmark: 4KB
> cluster.min-free-disk: 5%
> auto-delete: enable
>
>
> On Sun, Feb 4, 2018 at 9:44 PM, Amar Tumballi <atumball at redhat.com> wrote:
>
>> Thanks for the report Artem,
>>
>> Looks like the issue is about cache warming up. Specially, I suspect
>> rsync doing a 'readdir(), stat(), file operations' loop, where as when a
>> find or ls is issued, we get 'readdirp()' request, which contains the stat
>> information along with entries, which also makes sure cache is up-to-date
>> (at md-cache layer).
>>
>> Note that this is just a off-the memory hypothesis, We surely need to
>> analyse and debug more thoroughly for a proper explanation.  Some one in my
>> team would look at it soon.
>>
>> Regards,
>> Amar
>>
>> On Mon, Feb 5, 2018 at 7:25 AM, Vlad Kopylov <vladkopy at gmail.com> wrote:
>>
>>> You mounting it to the local bricks?
>>>
>>> struggling with same performance issues
>>> try using this volume setting
>>> http://lists.gluster.org/pipermail/gluster-users/2018-Januar
>>> y/033397.html
>>> performance.stat-prefetch: on might be it
>>>
>>> seems like when it gets to cache it is fast - those stat fetch which
>>> seem to come from .gluster are slow
>>>
>>> On Sun, Feb 4, 2018 at 3:45 AM, Artem Russakovskii <archon810 at gmail.com>
>>> wrote:
>>> > An update, and a very interesting one!
>>> >
>>> > After I started stracing rsync, all I could see was lstat calls, quite
>>> slow
>>> > ones, over and over, which is expected.
>>> >
>>> > For example: lstat("uploads/2016/10/nexus2c
>>> ee_DSC05339_thumb-161x107.jpg",
>>> > {st_mode=S_IFREG|0664, st_size=4043, ...}) = 0
>>> >
>>> > I googled around and found
>>> > https://gist.github.com/nh2/1836415489e2132cf85ed3832105fcc1, which is
>>> > seeing this exact issue with gluster, rsync and xfs.
>>> >
>>> > Here's the craziest finding so far. If while rsync is running (or right
>>> > before), I run /bin/ls or find on the same gluster dirs, it immediately
>>> > speeds up rsync by a factor of 100 or maybe even 1000. It's absolutely
>>> > insane.
>>> >
>>> > I'm stracing the rsync run, and the slow lstat calls flood in at an
>>> > incredible speed as soon as ls or find run. Several hundred of files
>>> per
>>> > minute (excruciatingly slow) becomes thousands or even tens of
>>> thousands of
>>> > files a second.
>>> >
>>> > What do you make of this?
>>> >
>>> >
>>> > _______________________________________________
>>> > Gluster-users mailing list
>>> > Gluster-users at gluster.org
>>> > http://lists.gluster.org/mailman/listinfo/gluster-users
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>>>
>>
>>
>>
>> --
>> Amar Tumballi (amarts)
>>
>> _______________________________________________
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>> Gluster-users at gluster.org
>> http://lists.gluster.org/mailman/listinfo/gluster-users
>>
>
>
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