Hi,All. The problem has occurred in my customer. poor performance with Context Switch Storm occurred with the following composition. Usually, CS is about 5000, WIPS=360. when CSStorm occurrence, CS is about 100000, WIPS=60 or less. (WIPS = number of web interactions per second)
It is under investigation using the patch which collects a LWLock. I suspected conflict of BufMappingLock. but, collected results are seen, occurrence of CSStorm and the increase of BufMappingLock counts seem not to correspond. Instead, SubtransControlLock and SubTrans were increasing. I do not understand what in the cause of CSStorm. [DB server]*1 Intel Xeon 3.0GHz*4(2CPU * H/T ON) 4GB Memory Red Hat Enterprise Linux ES release 4(Nahant Update 3) Linux version 2.6.9-34.ELsmp PostgreSQL8.1.3 (The version 8.2(head-6/15) was also occurred) shared_buffers=131072 temp_buffers=1000 max_connections=300 [AP server]*2 200 connection pooling. TPC-W model workload [Clinet]*4 TPC-W model workload (1) The following discussion were read. http://archives.postgresql.org/pgsql-hackers/2006-05/msg01003.php From: Tom Lane <tgl ( at ) sss ( dot ) pgh ( dot ) pa ( dot ) us> To: josh ( at ) agliodbs ( dot ) com Subject: Re: Further reduction of bufmgr lock contention Date: Wed, 24 May 2006 15:25:26 -0400 If there is a patch for investigation or a technique, would someone show it to me? (2) It seems that much sequential scan has occurred at CSStorm. When reading a tuple, do the visible satisfy check. it seems to generate the subtransaction for every transaction. How much is a possibility that the LWLock to a subtransaction cause CSStorm? best regards. -------- Katsuhiko Okano okano katsuhiko _at_ oss ntt co jp ---------------------------(end of broadcast)--------------------------- TIP 5: don't forget to increase your free space map settings
