Hi Sage, Thanks for your input. I will try those. Please see my response inline. Thanks & Regards Somnath -----Original Message----- From: Sage Weil [mailto:sage@xxxxxxxxxxx] Sent: Tuesday, September 24, 2013 3:47 PM To: Somnath Roy Cc: Travis Rhoden; Josh Durgin; ceph-devel@xxxxxxxxxxxxxxx; Anirban Ray; ceph-users@xxxxxxxxxxxxxx Subject: RE: [ceph-users] Scaling RBD module Hi Somnath! On Tue, 24 Sep 2013, Somnath Roy wrote: > > Hi Sage, > > We did quite a few experiment to see how ceph read performance can scale up. > Here is the summary. > > > > 1. > > First we tried to see how far a single node cluster with one osd can > scale up. We started with cuttlefish release and the entire osd file > system is on the ssd. What we saw with 4K size object and with single > rados client with dedicated 10G network, throughput can't go beyond a certain point. Are you using 'rados bench' to generate this load or something else? We've noticed that individual rados bench commands do not scale beyond a point but have never looked into it; the problem may be in the bench code and not in librados or SimpleMessenger. [Somnath] Yes, for generating load and measure the performance at the rados level. > We dig through the code and found out SimpleMessenger is opening > single socket connection (per client)to talk to the osd. Also, we saw > there is only one dispatcher Q (Dispatch thread)/ SimpleMessenger to > carry these requests to OSD. We started adding more dispatcher threads > in Dispatch Q, rearrange several locks in the Pipe.cc to identify the > bottleneck. What we end up discovering is that there is bottleneck > both in upstream as well as in the downstream at osd level and > changing the locking scheme in io path will affect lot of other codes (that we don't even know). > > So, we stopped that activity and started workaround the upstream > bottleneck by introducing more clients to the single OSD. What we saw > single OSD is scaling with lot of cpu utilization. To produce ~40K > iops (4K) it is taking almost 12 core of cpu. Just to make sure I understand: the single OSD dispatch queue does not become a problem with multiple clients? [Somnath] We saw with single client/single osd, if we increase the dispatch thread till 3, we were getting some improvement. But, not beyond 3. This is what we were also wondering !..But, looking at the architecture, it seems if the upstream bottleneck is removed this might be the next bottleneck. The next io request will not be in the OSD worker Q, till it completes OSD::ms_dispatch(). And there is lot of staff happening in this function. Now, top of the function it is taking osd level lock , so, increasing the threads is not helping, but, I think rearranging the locks will help here. Possibilities that come to mind: - DispatchQueue is doing some funny stuff to keep individual clients' messages ordered but to fairly process requests from multiple clients. There could easily be a problem with the per-client queue portion of this. - Pipe's use of MSG_MORE is making the TCP stream efficient... you might try setting 'ms tcp nodelay = false'. [Somnath] I will try this. - The message encode is happening in the thread that sends messages over the wire. Maybe doing it in send_message() instead of writer() will keep that on a separate core than the thread that's shoveling data into the socket. [Somnath] Are you telling to move the following code snippet from Pipe::writer() to SimpleMessenger::_send_message() ? // encode and copy out of *m m->encode(connection_state->get_features(), !msgr->cct->_conf->ms_nocrc); > Another point, I didn't see this single osd scale with the Dumpling > release with the multiple clients !! Something changed.. What is it with dumpling? [Somnath] We tried to compare but lot of changes , so, gave up :-(...But, I think eventually, if we want to increase the overall throughput we need to make individual osd efficient (both cpu/performance). So, we will definitely comeback to this. > 2. After that, we setup a proper cluster with 3 high performing > nodes and total 30 osds. Here also, we are seeing single rados bech > client as well as rbd client instance is not scaling beyond a certain > limit. It is not able to generate much load as node cpu utilization > remains very low. But running multiple client instance the performance is scaling till hit the cpu limit. > > So, it is pretty clear we are not able to saturate anything with > single client and that's why the 'noshare' option was very helpful to > measure the rbd performance benchmark. I have a single osd/single > client level call grind data attached here. Something from perf that shows a call graph would be more helpful to identify where things are waiting. We haven't done much optimizing at this level at all, so these results aren't entirely surprising. [Somnath] We will get this. > Now, I am doing the benchmark for radosgw and I think I am stuck with > similar bottleneck here. Could you please confirm that if radosgw also > opening single client instance to the cluster? It is: each radosgw has a single librados client instance. > If so, is there any similar option like 'noshare' in this case ? Here > also, creating multiple radosgw instance on separate nodes the > performance is scaling. No, but > BTW, is there a way to run multiple radosgw to a single node or it has > to be one/node ? yes. You just need to make sure they have different fastcgi sockets they listen on and probably set up a separate web server in front of each one. I think the next step to understanding what is going on is getting the right profiling tools in place so we can see where the client threads are spending their (non-idle and idle) time... [Somnath] How do you want me to do this ? Run profiler on rados bench ? sage > > > > Thanks & Regards > > Somnath > > > > > > > > -----Original Message----- > From: ceph-devel-owner@xxxxxxxxxxxxxxx > [mailto:ceph-devel-owner@xxxxxxxxxxxxxxx] On Behalf Of Sage Weil > Sent: Tuesday, September 24, 2013 2:16 PM > To: Travis Rhoden > Cc: Josh Durgin; ceph-devel@xxxxxxxxxxxxxxx; Anirban Ray; > ceph-users@xxxxxxxxxxxxxx > Subject: Re: [ceph-users] Scaling RBD module > > > > On Tue, 24 Sep 2013, Travis Rhoden wrote: > > > This "noshare" option may have just helped me a ton -- I sure wish I > > > would have asked similar questions sooner, because I have seen the > > > same failure to scale. =) > > > > > > One question -- when using the "noshare" option (or really, even > > > without it) are there any practical limits on the number of RBDs > > that > > > can be mounted? I have servers with ~100 RBDs on them each, and am > > > wondering if I switch them all over to using "noshare" if anything > > is > > > going to blow up, use a ton more memory, etc. Even without noshare, > > > are there any known limits to how many RBDs can be mapped? > > > > With noshare each mapped image will appear as a separate client > instance, which means it will have it's own session with teh monitors > and own TCP connections to the OSDs. It may be a viable workaround > for now but in general I would not recommend it. > > > > I'm very curious what the scaling issue is with the shared client. Do > you have a working perf that can capture callgraph information on this machine? > > > > sage > > > > > > > > Thanks! > > > > > > - Travis > > > > > > > > > On Thu, Sep 19, 2013 at 8:03 PM, Somnath Roy > > <Somnath.Roy@xxxxxxxxxxx> > > > wrote: > > > Thanks Josh ! > > > I am able to successfully add this noshare option in the image > > > mapping now. Looking at dmesg output, I found that was indeed > > > the secret key problem. Block performance is scaling now. > > > > > > Regards > > > Somnath > > > > > > -----Original Message----- > > > From: ceph-devel-owner@xxxxxxxxxxxxxxx > > > [mailto:ceph-devel-owner@xxxxxxxxxxxxxxx] On Behalf Of Josh > > > Durgin > > > Sent: Thursday, September 19, 2013 12:24 PM > > > To: Somnath Roy > > > Cc: Sage Weil; ceph-devel@xxxxxxxxxxxxxxx; Anirban Ray; > > > ceph-users@xxxxxxxxxxxxxx > > > Subject: Re: [ceph-users] Scaling RBD module > > > > > > On 09/19/2013 12:04 PM, Somnath Roy wrote: > > > > Hi Josh, > > > > Thanks for the information. I am trying to add the following > > > but hitting some permission issue. > > > > > > > > root@emsclient:/etc# echo > > > <mon-1>:6789,<mon-2>:6789,<mon-3>:6789 > > > > name=admin,key=client.admin,noshare test_rbd ceph_block_test' > > > > > > > > /sys/bus/rbd/add > > > > -bash: echo: write error: Operation not permitted > > > > > > If you check dmesg, it will probably show an error trying to > > > authenticate to the cluster. > > > > > > Instead of key=client.admin, you can pass the base64 secret > > > value as shown in 'ceph auth list' with the > > > secret=XXXXXXXXXXXXXXXXXXXXX option. > > > > > > BTW, there's a ticket for adding the noshare option to rbd map > > > so using the sysfs interface like this is never necessary: > > > > > > http://tracker.ceph.com/issues/6264 > > > > > > Josh > > > > > > > Here is the contents of rbd directory.. > > > > > > > > root@emsclient:/sys/bus/rbd# ll > > > > total 0 > > > > drwxr-xr-x 4 root root 0 Sep 19 11:59 ./ > > > > drwxr-xr-x 30 root root 0 Sep 13 11:41 ../ > > > > --w------- 1 root root 4096 Sep 19 11:59 add > > > > drwxr-xr-x 2 root root 0 Sep 19 12:03 devices/ > > > > drwxr-xr-x 2 root root 0 Sep 19 12:03 drivers/ > > > > -rw-r--r-- 1 root root 4096 Sep 19 12:03 drivers_autoprobe > > > > --w------- 1 root root 4096 Sep 19 12:03 drivers_probe > > > > --w------- 1 root root 4096 Sep 19 12:03 remove > > > > --w------- 1 root root 4096 Sep 19 11:59 uevent > > > > > > > > > > > > I checked even if I am logged in as root , I can't write > > > anything on /sys. > > > > > > > > Here is the Ubuntu version I am using.. > > > > > > > > root@emsclient:/etc# lsb_release -a > > > > No LSB modules are available. > > > > Distributor ID: Ubuntu > > > > Description: Ubuntu 13.04 > > > > Release: 13.04 > > > > Codename: raring > > > > > > > > Here is the mount information.... > > > > > > > > root@emsclient:/etc# mount > > > > /dev/mapper/emsclient--vg-root on / type ext4 > > > (rw,errors=remount-ro) > > > > proc on /proc type proc (rw,noexec,nosuid,nodev) sysfs on > >/sys > > > type > > > > sysfs (rw,noexec,nosuid,nodev) none on /sys/fs/cgroup type > > > tmpfs (rw) > > > > none on /sys/fs/fuse/connections type fusectl (rw) none on > > > > /sys/kernel/debug type debugfs (rw) none on > > > /sys/kernel/security type > > > > securityfs (rw) udev on /dev type devtmpfs (rw,mode=0755) > > > devpts on > > > > /dev/pts type devpts (rw,noexec,nosuid,gid=5,mode=0620) > > > > tmpfs on /run type tmpfs > >(rw,noexec,nosuid,size=10%,mode=0755) > > > > none on /run/lock type tmpfs > > > (rw,noexec,nosuid,nodev,size=5242880) > > > > none on /run/shm type tmpfs (rw,nosuid,nodev) none on > > > /run/user type > > > > tmpfs (rw,noexec,nosuid,nodev,size=104857600,mode=0755) > > > > /dev/sda1 on /boot type ext2 (rw) > > > > /dev/mapper/emsclient--vg-home on /home type ext4 (rw) > > > > > > > > > > > > Any idea what went wrong here ? > > > > > > > > Thanks & Regards > > > > Somnath > > > > > > > > -----Original Message----- > > > > From: Josh Durgin [mailto:josh.durgin@xxxxxxxxxxx] > > > > Sent: Wednesday, September 18, 2013 6:10 PM > > > > To: Somnath Roy > > > > Cc: Sage Weil; ceph-devel@xxxxxxxxxxxxxxx; Anirban Ray; > > > > ceph-users@xxxxxxxxxxxxxx > > > > Subject: Re: [ceph-users] Scaling RBD module > > > > > > > > On 09/17/2013 03:30 PM, Somnath Roy wrote: > > > >> Hi, > > > >> I am running Ceph on a 3 node cluster and each of my server > > > node is running 10 OSDs, one for each disk. I have one admin > > > node and all the nodes are connected with 2 X 10G network. One > > > network is for cluster and other one configured as public > > > network. > > > >> > > > >> Here is the status of my cluster. > > > >> > > > >> ~/fio_test# ceph -s > > > >> > > > >> cluster b2e0b4db-6342-490e-9c28-0aadf0188023 > > > >> health HEALTH_WARN clock skew detected on mon. > > > <server-name-2>, mon. <server-name-3> > > > >> monmap e1: 3 mons at > > > {<server-name-1>=xxx.xxx.xxx.xxx:6789/0, > > > <server-name-2>=xxx.xxx.xxx.xxx:6789/0, > > > <server-name-3>=xxx.xxx.xxx.xxx:6789/0}, election epoch 64, > > > quorum 0,1,2 <server-name-1>,<server-name-2>,<server-name-3> > > > >> osdmap e391: 30 osds: 30 up, 30 in > > > >> pgmap v5202: 30912 pgs: 30912 active+clean; 8494 MB > > > data, 27912 MB used, 11145 GB / 11172 GB avail > > > >> mdsmap e1: 0/0/1 up > > > >> > > > >> > > > >> I started with rados bench command to benchmark the read > > > performance of this Cluster on a large pool (~10K PGs) and > >found > > > that each rados client has a limitation. Each client can only > > > drive up to a certain mark. Each server node cpu utilization > > > shows it is around 85-90% idle and the admin node (from where > > > rados client is running) is around ~80-85% idle. I am trying > > > with 4K object size. > > > > > > > > Note that rados bench with 4k objects is different from rbd > > > with 4k-sized I/Os - rados bench sends each request to a new > > > object, while rbd objects are 4M by default. > > > > > > > >> Now, I started running more clients on the admin node and > >the > > > performance is scaling till it hits the client cpu limit. > >Server > > > still has the cpu of 30-35% idle. With small object size I > >must > > > say that the ceph per osd cpu utilization is not promising! > > > >> > > > >> After this, I started testing the rados block interface > >with > > > kernel rbd module from my admin node. > > > >> I have created 8 images mapped on the pool having around > >10K > > > PGs and I am not able to scale up the performance by running > >fio > > > (either by creating a software raid or running on individual > > > /dev/rbd* instances). For example, running multiple fio > > > instances (one in /dev/rbd1 and the other in /dev/rbd2) the > > > performance I am getting is half of what I am getting if > >running > > > one instance. Here is my fio job script. > > > >> > > > >> [random-reads] > > > >> ioengine=libaio > > > >> iodepth=32 > > > >> filename=/dev/rbd1 > > > >> rw=randread > > > >> bs=4k > > > >> direct=1 > > > >> size=2G > > > >> numjobs=64 > > > >> > > > >> Let me know if I am following the proper procedure or not. > > > >> > > > >> But, If my understanding is correct, kernel rbd module is > > > acting as a client to the cluster and in one admin node I can > > > run only one of such kernel instance. > > > >> If so, I am then limited to the client bottleneck that I > > > stated earlier. The cpu utilization of the server side is > >around > > > 85-90% idle, so, it is clear that client is not driving. > > > >> > > > >> My question is, is there any way to hit the cluster with > > > more client from a single box while testing the rbd module ? > > > > > > > > You can run multiple librbd instances easily (for example > >with > > > multiple runs of the rbd bench-write command). > > > > > > > > The kernel rbd driver uses the same rados client instance > >for > > > multiple block devices by default. There's an option (noshare) > > > to use a new rados client instance for a newly mapped device, > > > but it's not exposed by the rbd cli. You need to use the sysfs > > > interface that 'rbd map' uses instead. > > > > > > > > Once you've used rbd map once on a machine, the kernel will > > > already have the auth key stored, and you can use: > > > > > > > > echo '1.2.3.4:6789 name=admin,key=client.admin,noshare > > > poolname > > > > imagename' > /sys/bus/rbd/add > > > > > > > > Where 1.2.3.4:6789 is the address of a monitor, and you're > > > connecting as client.admin. > > > > > > > > You can use 'rbd unmap' as usual. > > > > > > > > Josh > > > > > > > > > > > > ________________________________ > > > > > > > > PLEASE NOTE: The information contained in this electronic > >mail > > > message is intended only for the use of the designated > > > recipient(s) named above. If the reader of this message is not > > > the intended recipient, you are hereby notified that you have > > > received this message in error and that any review, > > > dissemination, distribution, or copying of this message is > > > strictly prohibited. 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