Hi, If you set it on the MGS, it will be the new default for all the clients and new mount on the FS, the problem is you need LU-12759 (fixed in 2.12.4) on your clients since there was a bug on older clients and that setting was not working correctly.
On Mon, Nov 2, 2020 at 12:38 AM Tung-Han Hsieh < thhs...@twcp1.phys.ntu.edu.tw> wrote: > Dear Simon, > > Following your suggestions, now we confirmed that the problem of > dropping I/O performance of a client when there is a continous > I/O in the background is solved. It works charming. Thank you so > much !! > > Here is a final question. We found that this command: > > lctl set_param osc.*.grant_shrink=0 > > can be run the client, which fixed the value of "cur_grant_bytes" > to be the highest value 1880752127, and thereby fixed the problem. > Whenever we remount the file system (I mean, explicitly umount and > mount the file system), we need to execute this command again to > set it to zero. > > But this command: > > lctl set_param -P osc.*.grant_shrink=0 > > has to be run in the MGS node. Only setting it in MGS but without > setting in the client, it seems that the "cur_grant_bytes" of the > testing client still dropping under the background continous I/O. > So I am asking what's the meaning of this setting in MGS node. > > Thank you very much. > > > T.H.Hsieh > > On Fri, Oct 30, 2020 at 01:37:01PM +0800, Tung-Han Hsieh wrote: > > Dear Simon, > > > > Thank you very much for your useful information. Now we are arranging > > the system maintenance date in order to upgrade to Lustre-2.12.5. Then > > we will follow your suggestion to see whether this problem could be > > fixed. > > > > Here I report a test of under continuous I/O, how the cur_grant_bytes > > changed overtime. Again the client runs the following script for > > continuous reading in the background: > > > > # The Lustre file system was mounted under /home > > while [ 1 ]; do > > tar cf - /home/large/data | ssh remote_host "cat > /dev/null" > > done > > > > And every 20 mins, in the same client we copied a 600MB file from one > > directory to another within Lustre, and check the "cur_grant_bytes" by > > the following command running in the same client: > > > > /opt/lustre/sbin/lctl get_param osc.*.cur_grant_bytes > > > > The result is (every line separated by around 20 mins): > > > > osc.chome-OST0000-osc-ffff88a039150000.cur_grant_bytes=1880752127 > > osc.chome-OST0000-osc-ffff88a039150000.cur_grant_bytes=1410564096 > > osc.chome-OST0000-osc-ffff88a039150000.cur_grant_bytes=1059201024 > > osc.chome-OST0000-osc-ffff88a039150000.cur_grant_bytes=794400768 > > osc.chome-OST0000-osc-ffff88a039150000.cur_grant_bytes=595800576 > > osc.chome-OST0000-osc-ffff88a039150000.cur_grant_bytes=446850432 > > osc.chome-OST0000-osc-ffff88a039150000.cur_grant_bytes=335137824 > > osc.chome-OST0000-osc-ffff88a039150000.cur_grant_bytes=251353368 > > osc.chome-OST0000-osc-ffff88a039150000.cur_grant_bytes=188515026 > > osc.chome-OST0000-osc-ffff88a039150000.cur_grant_bytes=141386270 > > osc.chome-OST0000-osc-ffff88a039150000.cur_grant_bytes=106039703 > > osc.chome-OST0000-osc-ffff88a039150000.cur_grant_bytes=79529778 > > osc.chome-OST0000-osc-ffff88a039150000.cur_grant_bytes=59647334 > > osc.chome-OST0000-osc-ffff88a039150000.cur_grant_bytes=44735501 > > osc.chome-OST0000-osc-ffff88a039150000.cur_grant_bytes=33551626 > > osc.chome-OST0000-osc-ffff88a039150000.cur_grant_bytes=25163720 > > osc.chome-OST0000-osc-ffff88a039150000.cur_grant_bytes=18872790 > > osc.chome-OST0000-osc-ffff88a039150000.cur_grant_bytes=14154593 > > osc.chome-OST0000-osc-ffff88a039150000.cur_grant_bytes=10615945 > > osc.chome-OST0000-osc-ffff88a039150000.cur_grant_bytes=7961959 > > osc.chome-OST0000-osc-ffff88a039150000.cur_grant_bytes=5971470 > > osc.chome-OST0000-osc-ffff88a039150000.cur_grant_bytes=4478603 > > osc.chome-OST0000-osc-ffff88a039150000.cur_grant_bytes=3358953 > > osc.chome-OST0000-osc-ffff88a039150000.cur_grant_bytes=2519215 > > osc.chome-OST0000-osc-ffff88a039150000.cur_grant_bytes=1889412 > > osc.chome-OST0000-osc-ffff88a039150000.cur_grant_bytes=1417059 > > osc.chome-OST0000-osc-ffff88a039150000.cur_grant_bytes=1062795 > > osc.chome-OST0000-osc-ffff88a039150000.cur_grant_bytes=797097 > > osc.chome-OST0000-osc-ffff88a039150000.cur_grant_bytes=797097 > > .... > > > > The value 797097 seems to be the minimum. When it dropped to 1062795, > > the time of cp dramatically increased from around 1 sec to 1 min. In > > addition, during the test, the cluster is completely idling. And it > > is obvious that this test does not saturate the loading of both network > > and MDT / OST hardware (they have almost no loading). > > > > I am wondering whether this could be a bug to report to the development > > team. > > > > Best Regards, > > > > T.H.Hsieh > > > > On Thu, Oct 29, 2020 at 09:49:42AM -0400, Simon Guilbault wrote: > > > Our current workaround was to use the following command on the MGS with > > > Lustre 2.12.5 that include the patches in LU-12651 and LU-12759 (we > were > > > using a patched 2.12.4 a few months ago): > > > lctl set_param -P osc.*.grant_shrink=0 > > > > > > We could not find the root cause of the underlying problem, dynamic > grant > > > shrinking seems to be useful when the OSTs are running out of free > space. > > > > > > On Wed, Oct 28, 2020 at 11:47 PM Tung-Han Hsieh < > > > thhs...@twcp1.phys.ntu.edu.tw> wrote: > > > > > > > Dear Simon, > > > > > > > > Thank you very much for your hint. Yes, you are right. We compared > > > > the grant size of two client by (running in each client): > > > > > > > > lctl get_param osc.*.cur_grant_bytes > > > > > > > > - Client A: It has run the following large data transfer for over 36 > hrs. > > > > > > > > while [ 1 ]; do > > > > tar cf - /home/large/data | ssh remote_host "cat > > /dev/null" > > > > done > > > > > > > > The value of "cur_grant_bytes" is 796134. > > > > > > > > - Client B: It is almost idling during the action of Client A. > > > > > > > > The value of "cur_grant_bytes" is 1715863552. > > > > > > > > If this is the reason that hit the I/O performance of Client A > seriously, > > > > is it possible to maintain it at a constant value at least for the > head > > > > node (since the head node is the most probable one to have large and > long > > > > time data I/O of the whole cluster, especially for a data center) ? > > > > > > > > I would be also like to ask: Why this value has to be dynamically > adjusted > > > > ? > > > > > > > > Thank you very much for your comment in advance. > > > > > > > > Best Regards, > > > > > > > > T.H.Hsieh > > > > > > > > On Wed, Oct 28, 2020 at 02:00:21PM -0400, Simon Guilbault wrote: > > > > > Hi, we had a similar performance problem on our login/DTNs node a > few > > > > > months ago, the problem was the grant size was shrinking and was > getting > > > > > stuck under 1MB. Once under 1MB, the client had to send every > request to > > > > > the OST using sync IO. > > > > > > > > > > Check the output of the following command: > > > > > lctl get_param osc.*.cur_grant_bytes > > > > > > > > > > On Wed, Oct 28, 2020 at 12:08 AM Tung-Han Hsieh < > > > > > thhs...@twcp1.phys.ntu.edu.tw> wrote: > > > > > > > > > > > Dear All, > > > > > > > > > > > > Sorry that I am not sure whether this mail was successfully > posted to > > > > > > the lustre-discuss mailing list or not. So I resent it again. > Please > > > > > > ignore it if you already read it before. > > > > > > > > > > > > > > > > > =========================================================================== > > > > > > > > > > > > Dear Andreas, > > > > > > > > > > > > Thank you very much for your kindly suggestions. These days I > got a > > > > chance > > > > > > to follow your suggestions for the test. This email is to report > the > > > > > > results > > > > > > I have done so far. What I have done were: > > > > > > > > > > > > 1. Upgrade one client (with Infiniband) to Lustre > 2.13.56_44_gf8a8d3f > > > > > > (obtained from github). The compiling information is: > > > > > > > > > > > > - Linux kernel 4.19.123. > > > > > > - Infiniband MLNX_OFED_SRC-4.6-1.0.1.1. > > > > > > - ./configure --prefix=/opt/lustre \ > > > > > > --with-o2ib=/path/of/mlnx-ofed-kernel-4.6 \ > > > > > > --disable-server --enable-mpitests=no > > > > > > - make > > > > > > - make install > > > > > > > > > > > > 2. We mounted the lustre file system (lustre MDT/OST servers: > version > > > > > > 2.12.4 with Infiniband with ZFS backend) by this command: > > > > > > > > > > > > - mount -t lustre -o flock mdt@o2ib:/chome /home > > > > > > > > > > > > 3. The script to simulate large data transfer is following: > > > > > > (the directory "/home/large/data" contains 758 files, each > size > > > > 600MB) > > > > > > > > > > > > while [ 1 ]; do > > > > > > tar cf - /home/large/data | ssh remote_host "cat > > /dev/null" > > > > > > done > > > > > > > > > > > > ps. Note that this scenario is common in a large data center, > while > > > > > > some users transferring large data out of the data center > > > > through > > > > > > the head node; while other users might copy files and do > their > > > > > > normal works in the same head node. > > > > > > > > > > > > 4. During the data transfer in the background, I occationally > ran this > > > > > > command in the same client to test whether there is any > abnormality > > > > > > in I/O performance (where /home/dir1/file has size 600MB): > > > > > > > > > > > > cp /home/dir1/file /home/dir2/ > > > > > > > > > > > > In the beginning this command can complete in about 1 sec. > But after > > > > > > around 18 hours (not exactly, because the test ran overnight > while > > > > > > I was sleeping), the problem appeared. The time to complete > the same > > > > > > cp command was more than 1 minute. > > > > > > > > > > > > During the test, I am sure that the whole cluster was idling. > The > > > > MDT > > > > > > and OST servers did not have other loading. The CPU usage of > the > > > > testing > > > > > > client was below 0.3. > > > > > > > > > > > > Then I stopped the test, and let the whole system completely > idle. > > > > But > > > > > > after 3 hours, the I/O abnormality of the same "cp" command > was > > > > still > > > > > > there. Only after I unmounted /home and remounted /home, the > > > > abnormality > > > > > > of "cp" recovered to normal. > > > > > > > > > > > > Before and after remounting /home (which I call "reset"), I did > the > > > > > > following tests: > > > > > > > > > > > > 1. Using "top" to check the memory usage: > > > > > > > > > > > > Before reset: > > > > > > ===================================== > > > > > > top - 10:43:15 up 35 days, 52 min, 3 users, load average: > 0.00, 0.00, > > > > > > 0.00 > > > > > > Tasks: 404 total, 1 running, 162 sleeping, 0 stopped, 0 > zombie > > > > > > %Cpu(s): 0.0 us, 0.0 sy, 0.0 ni,100.0 id, 0.0 wa, 0.0 hi, > 0.0 si, > > > > > > 0.0 st > > > > > > KiB Mem : 13232632+total, 13000131+free, 647784 used, 1677220 > > > > buff/cache > > > > > > KiB Swap: 15631240 total, 15631240 free, 0 used. > 13076376+avail > > > > Mem > > > > > > > > > > > > After reset: > > > > > > ===================================== > > > > > > top - 10:48:02 up 35 days, 57 min, 3 users, load average: > 0.04, 0.01, > > > > > > 0.00 > > > > > > Tasks: 395 total, 1 running, 159 sleeping, 0 stopped, 0 > zombie > > > > > > %Cpu(s): 0.0 us, 0.0 sy, 0.0 ni,100.0 id, 0.0 wa, 0.0 hi, > 0.0 si, > > > > > > 0.0 st > > > > > > KiB Mem : 13232632+total, 12946539+free, 675948 used, 2184976 > > > > buff/cache > > > > > > KiB Swap: 15631240 total, 15631240 free, 0 used. > 13073571+avail > > > > Mem > > > > > > > > > > > > It seems that most of the memory were in "free" state. The > amount of > > > > > > hidden memory was neglectable. So I did not further > investigate the > > > > > > amount of slab memory. > > > > > > > > > > > > 2. Using "strace" with the following commands: > > > > > > > > > > > > - Before reset (took 1 min of each cp): > > > > > > strace -c -o /tmp/log2-err.txt cp /home/dir1/file > /home/dir2/ > > > > > > > > > > > > - After reset (took 1 sec of each cp): > > > > > > strace -c -o /tmp/log2-reset.txt cp /home/dir1/file > /home/dir2/ > > > > > > > > > > > > From the log files, the major time consuming was read and > write > > > > > > syscalls. > > > > > > The others are neglectable. > > > > > > > > > > > > % time seconds usecs/call calls errors syscall > > > > > > ------ ----------- ----------- --------- --------- > ---------------- > > > > > > (Before reset) > > > > > > 71.46 0.278424 1920 145 write > > > > > > 28.06 0.109322 705 155 read > > > > > > (After reset) > > > > > > 52.92 0.299091 2063 145 write > > > > > > 46.85 0.264777 1708 155 read > > > > > > > > > > > > Before reset, since we have done the cp test for the same > file a > > > > > > few times, the file was already cached. So the reading time is > > > > > > smaller before reset than that after reset (since after reset > /home > > > > > > was remounted). > > > > > > > > > > > > Hence from this result, the time of syscalls looks normal. The > > > > > > performance drop seems occuring in other places. > > > > > > > > > > > > Now I haven't done the investigation of Lustre kernel debug log > by > > > > enabling > > > > > > Lustre debug=-1. We will find another chance to do it. > > > > > > > > > > > > Up to now, any comments or suggestions are very welcome. > > > > > > > > > > > > Thanks for your help in advance. > > > > > > > > > > > > > > > > > > Best Regards, > > > > > > > > > > > > T.H.Hsieh > > > > > > > > > > > > > > > > > > On Thu, Oct 08, 2020 at 01:32:53PM -0600, Andreas Dilger wrote: > > > > > > > On Oct 8, 2020, at 10:37 AM, Tung-Han Hsieh < > > > > > > thhs...@twcp1.phys.ntu.edu.tw> wrote: > > > > > > > > > > > > > > > > Dear All, > > > > > > > > > > > > > > > > In the past months, we encountered several times of Lustre > I/O > > > > > > abnormally > > > > > > > > slowing down. It is quite mysterious that there seems no > problem > > > > on the > > > > > > > > network hardware, nor the lustre itself since there is no > error > > > > message > > > > > > > > at all in MDT/OST/client sides. > > > > > > > > > > > > > > > > Recently we probably found a way to reproduce it, and then > have > > > > some > > > > > > > > suspections. We found that if we continuously perform I/O on > a > > > > client > > > > > > > > without stop, then after some time threshold (probably more > than 24 > > > > > > > > hours), the additional file I/O bandwidth of that client > will be > > > > > > shriked > > > > > > > > dramatically. > > > > > > > > > > > > > > > > Our configuration is the following: > > > > > > > > - One MDT and one OST server, based on ZFS + Lustre-2.12.4. > > > > > > > > - The OST is served by a RAID 5 system with 15 SAS hard > disks. > > > > > > > > - Some clients connect to MDT/OST through Infiniband, some > through > > > > > > > > gigabit ethernet. > > > > > > > > > > > > > > > > Our test was focused on the clients using infiniband, which > is > > > > > > described > > > > > > > > in the following: > > > > > > > > > > > > > > > > We have a huge (several TB) amount of data stored in the > Lustre > > > > file > > > > > > > > system to be transferred to outside network. In order not to > > > > exhaust > > > > > > > > the network bandwidth of our institute, we transfer the data > with > > > > > > limited > > > > > > > > bandwidth via the following command: > > > > > > > > > > > > > > > > rsync -av --bwlimit=1000 <data_in_Lustre> > > > > > > <out_side_server>:/<out_side_path>/ > > > > > > > > > > > > > > > > That is, the transferring rate is 1 MB per second, which is > > > > relatively > > > > > > > > low. The client read the data from Lustre through > infiniband. So > > > > during > > > > > > > > data transmission, presumably there is no problem to do > other data > > > > I/O > > > > > > > > on the same client. On average, when copy a 600 MB file from > one > > > > > > directory > > > > > > > > to another directory (both in the same Lustre file system), > it took > > > > > > about > > > > > > > > 1.0 - 2.0 secs, even when the rsync process still working. > > > > > > > > > > > > > > > > But after about 24 hours of continuously sending data via > rsync, > > > > the > > > > > > > > additional I/O on the same client was dramatically shrinked. > When > > > > it > > > > > > happens, > > > > > > > > it took more than 1 minute to copy a 600 MB from somewhere to > > > > another > > > > > > place > > > > > > > > (both in the same Lustre) while rsync is still running. > > > > > > > > > > > > > > > > Then, we stopped the rsync process, and wait for a while > (about one > > > > > > > > hour). The I/O performance of copying that 600 MB file > returns > > > > normal. > > > > > > > > > > > > > > > > Based on this observation, we are suspecting that whether > there is > > > > a > > > > > > > > hidden QoS mechanism built in Lustre ? When a process > occupies the > > > > I/O > > > > > > > > bandwidth for a long time and exceeded some limits, does > Lustre > > > > > > automatically > > > > > > > > shrinked the I/O bandwidth for all processes running in the > same > > > > > > client ? > > > > > > > > > > > > > > > > I am not against such QoS design, if it does exist. But the > amount > > > > of > > > > > > > > shrinking seems to be too large for infiniband (QDR and > above). > > > > Then > > > > > > > > I am further suspecting that whether this is due to that our > > > > system is > > > > > > > > mixed with clients in which some have infiniband but some do > not ? > > > > > > > > > > > > > > > > Could anyone help to fix this problem ? Any suggestions will > be > > > > very > > > > > > > > appreciated. > > > > > > > > > > > > > > There is no "hidden QOS", unless it is so well hidden that I > don't > > > > know > > > > > > > about it. > > > > > > > > > > > > > > You could investigate several different things to isolate the > > > > problem: > > > > > > > - try with a 2.13.56 client to see if the problem is already > fixed > > > > > > > - check if the client is using a lot of CPU when it becomes > slow > > > > > > > - run strace on your copy process to see which syscalls are > slow > > > > > > > - check memory/slab usage > > > > > > > - enable Lustre debug=-1 and dump the kernel debug log to see > where > > > > > > > the process is taking a long time to complete a request > > > > > > > > > > > > > > It is definitely possible that there is some kind of problem, > since > > > > this > > > > > > > is not a very common workload to be continuously writing to > the same > > > > file > > > > > > > descriptor for over a day. You'll have to do the > investigation on > > > > your > > > > > > > system to isolate the source of the problem. > > > > > > > > > > > > > > Cheers, Andreas > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > _______________________________________________ > > > > > > lustre-discuss mailing list > > > > > > lustre-discuss@lists.lustre.org > > > > > > http://lists.lustre.org/listinfo.cgi/lustre-discuss-lustre.org > > > > > > > > > > >
_______________________________________________ lustre-discuss mailing list lustre-discuss@lists.lustre.org http://lists.lustre.org/listinfo.cgi/lustre-discuss-lustre.org
