Re: Re: [firebird-support] Re: [FB 2.1] Firebird engine seems to slow down on high load without utilizing hardware
soryy not Shane but Sean regards, karol Bieniaszewski
Re: [firebird-support] Re: [FB 2.1] Firebird engine seems to slow down on high load without utilizing hardware
>>1) We do monitor the transaction gab and if needed, we interact. how often and how? By MON$ tables or you read header page? >>2) We do run gbak daily. We do not use nbackup - we would like to and tried >>it but it's corrupting the db. and this slowdown is not in time of backup i suppose? Will be good if you can test this corruption scenario on newer firebird version - especially on FB3. And send us your feedback. >>3) We do use read-only readcommited transactions with record versioning as >>much as we can. >>Otherwise, same Settings but not read-only. good More questions: 1. as Shane ask what is your CPU utilization % but per core? 2. how do you checked that your system slowdown? Some queries are slower or all queries are slower. Did you run some monitoring throught MON$ tables ten? 3. and same as Shane ask - how often do you run manual sweep? And did you consider to change FB to newer version In new version sweep was optimized and do not visit unnescessary pages. page contain now flag if sweep is needed. 4. What is your TempCacheLimit? 5. and i am also interested about disc test with cristalmark regards, Karol Bieniaszewski
RE: [firebird-support] Re: [FB 2.1] Firebird engine seems to slow down on high load without utilizing hardware
> 1) We have sweep set to 0. We do monitor the transaction gab and if > needed, we interact. Any kind of automatic sweep under high load will kill > the server :) 1- Do you run a manual sweep on a regular basis? 2- What is the CPU % like when Firebird "slows down"? 3- Have you tried using CrystalDiskMark to measure your disk IOPs? My local workstation SSD results are: --- CrystalDiskMark 5.0.2 x64 (C) 2007-2015 hiyohiyo --- Sequential Read (Q= 2,T= 4) : 564.293 MB/s Sequential Write (Q= 2,T= 4) : 535.874 MB/s Random Read 4KiB (Q=256,T= 1) : 227.652 MB/s [ 55579.1 IOPS] Random Write 4KiB (Q=256,T= 1) : 195.258 MB/s [ 47670.4 IOPS] Sequential Read (T= 1) : 545.480 MB/s Sequential Write (T= 1) : 520.939 MB/s Random Read 4KiB (Q= 1,T= 1) :36.577 MB/s [ 8929.9 IOPS] Random Write 4KiB (Q= 1,T= 1) :90.805 MB/s [ 22169.2 IOPS] 3- Have you tried to analyze/determine the long running SQLs being executed, to determine if wrong/no indexes are being used by queries or other optimizations that could be made? Sean
[firebird-support] Re: [FB 2.1] Firebird engine seems to slow down on high load without utilizing hardware
We splitted our system now to 2 databases, reducing the connections to about 250 per DB. Running on same Hardware (same SAN-Storage) and splitted the CPU ressources. Both system seems stable now, but that's not really a solution we prefered. Just helps us to not lose customers at the moment.
[firebird-support] Re: [FB 2.1] Firebird engine seems to slow down on high load without utilizing hardware
1) We have sweep set to 0. We do monitor the transaction gab and if needed, we interact. Any kind of automatic sweep under high load will kill the server :) 2) We do run gbak daily. We do not use nbackup - we would like to and tried it but it's corrupting the db. 3) We do use read-only readcommited transactions with record versioning as much as we can. Otherwise, same Settings but not read-only.
[firebird-support] Re: [FB 2.1] Firebird engine seems to slow down on high load without utilizing hardware
Hey Thomas, thanks for your extensive reply. Unfortunatly we'r still bound to some old 32bit UDF functionality which we can't get in 64bit. I think you know about the use of SuperClassic with 32bit Server - 2GB RAM Limit :) It's not impossible, but also not really a fast route we can go. But for sure again a reason to talk about moving the switch to 2.5. We did ran some some disk IO benchmarks (with AS SSD) today, and in times of SSD kinda depressing :D The thing is, sure this numbers look really low. But the system never uses it. The monitoring of the SAN show's that this load's are never used. The Single-4k-read is worring me, but i lean towards that our 500 proceses are more like the 64-thread test. But even then, we only messured 100 Iops reading on livesystem. Sequential Read speed: ~ 450 MB / s Sequential Write speed: ~500 MB / s 4k read: 196 Iops 4k write: 1376 Iops 4k-64 thread read: 15945 Iops 4k-64 thread write: 7361 Iops Garbage Info still needs to be collected. But first signs show that this indeed could be a potential problem. From Sintatica, every 20 Minutes a Peak in GC for ~15.000 transactions. This get's fixed by the server in the relative small amount of time (i think < 1 minute), since it's really only a single peak in the graph everytime. When the GC stop increasing and the server starts to collect it, we see an increase of concurrent running transactions (= transactions are longer open and processed slower). We don't have data from the live system yet to see if this behaviour kind of "snowballs" when there is really high load on the server. Best Regards, ---In firebird-support@yahoogroups.com, wrote : Hi Patrick, > Hi Thomas, nice to get a response from you. We already met in ~2010 in Linz > at > your office :) > (ex. SEM GmbH, later Playmonitor GmbH) I know. XING (Big Brother) is watching you. Nice to see that you are still running with Firebird. ;-) > First, sorry for posting a mixed state of informations. The config settings i > postet are the current settings. > But the Lock-Table-Header was from last saturday (day of total system crash) > - > we changed Hash Slot Value since than, but it didn't work. New Table looks > like: > > > LOCK_HEADER BLOCK > Version: 16, Active owner: 0, Length: 134247728, Used: 55790260 > Semmask: 0x0, Flags: 0x0001 > Enqs: 1806423519, Converts: 4553851, Rejects: 5134185, Blocks: 56585419 > Deadlock scans: 82, Deadlocks: 0, Scan interval: 10 > Acquires: 2058846891, Acquire blocks: 321584126, Spin count: 0 > Mutex wait: 15.6% > Hash slots: 20011, Hash lengths (min/avg/max): 0/ 7/ 18 > Remove node: 0, Insert queue: 0, Insert prior: 0 > Owners (297): forward: 385160, backward: 38086352 > Free owners (43): forward: 52978748, backward: 20505128 > Free locks (41802): forward: 180712, backward: 3620136 > Free requests (-1097572396): forward: 46948676, backward: 13681252 > Lock Ordering: Enabled > > > The Min/Avg/Max hash lengths look better now, but as you mentioned the Mutex > wait is worring us too. > We have 2 direct questions about that. > > > 1) What are the negative effects of increasing Hash-Slots (too high)? It somehow defines the initial size of a hash table which is used for lock(ed) object lookup by a key (= hash value), ideally with constant O(1) run-time complexity. If the hash table is too small, due to a too small value for hash slots, it starts to degenerate into a linked/linear list per hash slot. Worst case resulting in O(n) complexity for lookups. The above 20011 setting shows an AVG hash length which looks fine. As you might know, Classic having a dedicated process per connection model somehow needs a (global) mechanism to synchronize/protect shared data structures across these processes via IPC. This is what the lock manager and the lock table is used for. > 2) As far as we know, we can't influence Mutex wait directly (it's just > informational). But do you think that's the reason the underlying hardware is > not utilized? I don't think you are disk IO bound. Means, I'm not convinced that faster IO will help. Somehow backed by the high mutex wait. Under normal operations you see 100-500 IOPS with some room for further increase as shown in the 1700 IOPS backup use case. Don't know how random disk IO is in this two scenarios. Any chance to run some sort of disk IO benchmarks or do you already know your upper limits for your SAN IOPS wise? > > > We do consider to upgrade to 2.5, but had our eyes on FB 3 over the last > year, > waiting for it to get ready. > With 2.5.x we tested around a long time now, but never found a real reason to > upgrade - since it's a reasonable amount of work for us. When you say it > improves the lock contention, this sound pretty good. But again the question, > do you think lock contention is limiting our system? Dmitry, Vlad etc. will correct me (in case he is following the thread), but I recall t
[firebird-support] Re: [FB 2.1] Firebird engine seems to slow down on high load without utilizing hardware
Hey Alexey, thanks you for our input. I think what you say is correct, and we reviewed our disk setup again. We are utilizing mechnical discs so it's kinda hard to compare SSD performance to them. But they should provide enought IOPS for our load. Unfortunatly we can't just switch to a single SSD, since we would loose replication and failover systems the SAN provides which is a critical demand for us. I'm afraid for now we have to stick with it, until we have some facts to proof that the SAN Setup is our limiting factor. And data is not should that for me currently. On a sidenode, we do own a server with SSD setup, but in tests we couldn't get a noticable performance gain through increasement of IOs this way. (tests was generic and not real world load unfortunatly) Best Regards, Patrick ---In firebird-support@yahoogroups.com, wrote : Hi Patrick, If you say that problem occurred recently, I would suggest you to check SAN disks health. However, these values >Average system IOPS under load read: 100 >Average system IOPS under load write: 550 >Backup Restore IOPS read: 1700 >Backup Restore IOPS write: 250 are really, really low. 1700 IOPS for the database with 4k page means 6.8Mb/sec (in case of random reads). I suggest to install a single SSD drive and check how it will work. SSD IOPS looks like Random Read 4KB (QD=32) : 283.050 MB/s [ 69104.0 IOPS] Random Write 4KB (QD=32) : 213.837 MB/s [ 52206.2 IOPS] From our optimization practice we found that if you need to optimize only the single instance of the database, the most cost effective way is to upgrade to SSD first, and only then fix other problems. Regards, Alexey Kovyazin IBSurgeon HQbird www.ib-aid.com http://www.ib-aid.com hi, recently we had some strange performance issues with our Firebird DB server. On high load, our server started to slow down. Select and update SQL query times did go up by more than 500% on average, but reaching unreasonable high execution times at worst case. (several minutes instead of < 1sec) OIT/OAT/Next Transaction statistics was within 1000 the hole time We were not able to messure any hardware limiting factor. Indeed, this system was running with only 8 cores at about 70% CPU usage on max. load. We decided that this may be our problem since we experienced a similar problem at about 80% CPU load in the past. So we upgraded the hardware. As expected, the CPU-load dropped to ~35% usage on max. load scenario. But this did not solve the problem. Same story for the harddisk system. The usage is not even near it's max capacity. We also can't see any impact on the harddisk. We'r kind of stuck with our ideas, because we have no idea what could be a potential bottleneck to the system. Since the hardware doesn't show a limit, there have to be anything else - most likely firebird engine related that's limiting our system. We would be very grateful if anyone can give us hints where we can search further. Or someone has similar experiences to share with us. Operating System: Windows Server 2003 Firebird: 2.1.5 Classic Dedicated database server (VMWare) CPU: 16 cores, each 2.4 GHz RAM: 32 GB About 14GB are used from OS and firebird processes under max load. HDD: SAN Storage System Average system IOPS under load read: 100 Average system IOPS under load write: 550 Backup Restore IOPS read: 1700 Backup Restore IOPS write: 250 SAN IPOS Limit (max): 3000 Firebird Config Settings, based on defaults DefaultDbCachePages = 1024 LockMemSize = 134247728 LockHashSlots = 20011 Database size: about 45 GB 450 to 550 concurrent connections Daily average of 65 transactions / second (peak should be higher) FB_LOCK_PRINT (without any params) while system was slowing down (~4 days uptime). I have to note, Firebird was not able to print the complete output (stats was not cropped by me) LOCK_HEADER BLOCK Version: 16, Active owner: 0, Length: 134247728, Used: 82169316 Semmask: 0x0, Flags: 0x0001 Enqs: 4211018659, Converts: 10050437, Rejects: 9115488, Blocks: 105409192 Deadlock scans: 1049, Deadlocks: 0, Scan interval: 10 Acquires: 4723416170, Acquire blocks: 640857597, Spin count: 0 Mutex wait: 13.6% Hash slots: 15077, Hash lengths (min/avg/max):3/ 12/ 25 Remove node: 0, Insert queue: 36, Insert prior: 74815332 Owners (456): forward: 131316, backward: 14899392 Free owners (9): forward: 39711576, backward: 49867232 Free locks (42409): forward: 65924212, backward: 23319052 With best Regards, Patrick Friessnegg Synesc GmbH
