Hi,
I would like to update this thread for others struggling with cache pressure.
The last time we hit that message was more than three weeks ago
(workload has not changed), so it seems as our current configuration
is fitting our workload.
Reducing client_oc_size to 100 MB (from default 200 MB) seems to be
the trick here, just increasing the cache size was not enough, at
least not if you are limited in memory. Currently we have set
mds_cache_memory_limit to 4 GB.
Another note on MDS cache size:
I had configured the mds_cache_memory_limit (4 GB) and client_oc_size
(100 MB) in version 12.2.5. Comparing the real usage with "ceph daemon
mds.<MDS> cache status" and the reserved memory with "top" I noticed a
huge difference, the reserved memory was almost 8 GB while "cache
status" was at nearly 4 GB.
After upgrading to 12.2.7 the reserved memory size in top is still
only about 5 GB after one week. Obviously there have been improvements
regarding memory consumption of MDS, which is nice. :-)
Regards,
Eugen
Zitat von Eugen Block <eblock@xxxxxx>:
Hi,
I think it does have positive effect on the messages. Cause I get fewer
messages than before.
that's nice. I also receive definitely less cache pressure messages
than before.
I also started to play around with the client side cache
configuration. I halved the client object cache size from 200 MB to
100 MB:
ceph@host1:~ $ ceph daemon mds.host1 config set client_oc_size 104857600
Although I still encountered one pressure message recently the total
amount of these messages has decreased significantly.
Regards,
Eugen
Zitat von Zhenshi Zhou <deaderzzs@xxxxxxxxx>:
Hi Eugen,
I think it does have positive effect on the messages. Cause I get fewer
messages than before.
Eugen Block <eblock@xxxxxx> 于2018年8月20日周一 下午9:29写道：
Update: we are getting these messages again.
So the search continues...
Zitat von Eugen Block <eblock@xxxxxx>:
Hi,
Depending on your kernel (memory leaks with CephFS) increasing the
mds_cache_memory_limit could be of help. What is your current
setting now?
ceph:~ # ceph daemon mds.<MDS> config show | grep mds_cache_memory_limit
We had these messages for months, almost every day.
It would occur when hourly backup jobs ran and the MDS had to serve
an additional client (searching the whole CephFS for changes)
besides the existing CephFS clients. First we updated all clients to
a more recent kernel version, but the warnings didn't stop. Then we
doubled the cache size from 2 GB to 4 GB last week and since then I
haven't seen this warning again (for now).
Try playing with the cache size to find a setting fitting your
needs, but don't forget to monitor your MDS in case something goes
wrong.
Regards,
Eugen
Zitat von Wido den Hollander <wido@xxxxxxxx>:
On 08/13/2018 01:22 PM, Zhenshi Zhou wrote:
Hi,
Recently, the cluster runs healthy, but I get warning messages
everyday:
Which version of Ceph? Which version of clients?
Can you post:
$ ceph versions
$ ceph features
$ ceph fs status
Wido
2018-08-13 17:39:23.682213 [INF] Cluster is now healthy
2018-08-13 17:39:23.682144 [INF] Health check cleared:
MDS_CLIENT_RECALL (was: 6 clients failing to respond to cache pressure)
2018-08-13 17:39:23.052022 [INF] MDS health message cleared (mds.0):
Client docker38:docker failing to respond to cache pressure
2018-08-13 17:39:23.051979 [INF] MDS health message cleared (mds.0):
Client docker73:docker failing to respond to cache pressure
2018-08-13 17:39:23.051934 [INF] MDS health message cleared (mds.0):
Client docker74:docker failing to respond to cache pressure
2018-08-13 17:39:23.051853 [INF] MDS health message cleared (mds.0):
Client docker75:docker failing to respond to cache pressure
2018-08-13 17:39:23.051815 [INF] MDS health message cleared (mds.0):
Client docker27:docker failing to respond to cache pressure
2018-08-13 17:39:23.051753 [INF] MDS health message cleared (mds.0):
Client docker27 failing to respond to cache pressure
2018-08-13 17:38:11.100331 [WRN] Health check update: 6 clients
failing
to respond to cache pressure (MDS_CLIENT_RECALL)
2018-08-13 17:37:39.570014 [WRN] Health check update: 5 clients
failing
to respond to cache pressure (MDS_CLIENT_RECALL)
2018-08-13 17:37:31.099418 [WRN] Health check update: 3 clients
failing
to respond to cache pressure (MDS_CLIENT_RECALL)
2018-08-13 17:36:34.564345 [WRN] Health check update: 1 clients
failing
to respond to cache pressure (MDS_CLIENT_RECALL)
2018-08-13 17:36:27.121891 [WRN] Health check update: 3 clients
failing
to respond to cache pressure (MDS_CLIENT_RECALL)
2018-08-13 17:36:11.967531 [WRN] Health check update: 5 clients
failing
to respond to cache pressure (MDS_CLIENT_RECALL)
2018-08-13 17:35:59.870055 [WRN] Health check update: 6 clients
failing
to respond to cache pressure (MDS_CLIENT_RECALL)
2018-08-13 17:35:47.787323 [WRN] Health check update: 3 clients
failing
to respond to cache pressure (MDS_CLIENT_RECALL)
2018-08-13 17:34:59.435933 [WRN] Health check failed: 1 clients
failing
to respond to cache pressure (MDS_CLIENT_RECALL)
2018-08-13 17:34:59.045510 [WRN] MDS health message (mds.0): Client
docker75:docker failing to respond to cache pressure
How can I fix it?
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