RE: Slow performance after shmem dynamically allocated

How many segments does 'onstat -g seg' show? If there are more than four, then you could be having some performance issues. It's all in the way that HP handles memory; it can't have more than three memory segments active in the OS at one time. Here's a snip of my current production system ---------------------------------------------------------------------------- ------------ noahsark:/home/dvp/mis_95/sql> onstat -g seg Informix Dynamic Server Version 7.30.UC7 -- On-Line -- Up 2 days 12:40:39 -- 437240 Kbytes Segment Summary: id key addr size ovhd class blkused blkfree 6 1381451777 c1461000 347062272 7744 R 42359 7 (shared) 1381451777 d5f5d000 100671488 2148 V 7299 4990 7 1381451778 dbf5f000 2777088 652 M 333 6 8 1381451779 dc205000 2777088 652 M 331 8 Total: - - 453287936 - - 50322 5011 (* segment locked in memory) noahsark:/home/dvp/mis_95/sql> ipcs -m | grep informix m 6 0x52574801 --rw-rw---- root informix m 7 0x52574802 --rw-rw-rw- root informix m 8 0x52574803 --rw-rw-rw- root informix There are only three segments active in the OS: ids 6, 7, and 8. 6 corresponds to the resident and virtual memory segments for Informix, while 7 and 8 correspond to the Informix message queues. When Informix allocates another segment of virtual memory, it allocates it as a separate segment to the OS as well. In HPUX, when that fourth segment is allocated, you can get some performance hits. If possible, use onmode -F to free unused memory segments. John Carlson Informix DBA EDS - WHSmith USA 3200 Windy Hill Road, Suite 1500 West Atlanta, GA 30330 > -----Original Message----- > From: Colleen M. Morrow [mailto:cmmorrow@JonesDay.com] > Sent: Tuesday, October 03, 2000 10:35 AM > To: informix-list@iiug.org > Subject: Slow performance after shmem dynamically allocated > > > > _______________________________________________________________ > > This message and any attachments are intended for the > individual or entity > named above. If you are not the intended recipient, please > do not read, > copy, use or disclose this communication to others; also > please notify the > sender by replying to this message, and then delete it from > your system. > Thank you. > _______________________________________________________________ > > I've heard that there was a bug in previous versions of IDS that > performance suffered after a new Virtual Memory segment was > dynamically > allocated. We're using 7.31.UC6 on HP 10.20. Does anyone know of any > problems with that in this version? TIA. > > BTW, please respond directly to this address, thanks. > > Colleen >

Check the FAQ and www.smooth1.demon.co.uk. It is because the CPU on HP-UX machine only has three segment registers and so efffectively a type of 'swapping' occurs if a process has more than three shared memory segments attached to it. A fundamental bug in the design of the CPU! Any plans for HP to fix it? John Carlson wrote in message <8rd46v$ilr$1@news.xmission.com>... > >How many segments does 'onstat -g seg' show? If there are more than four, >then you could be having some performance issues. It's all in the way that >HP handles memory; it can't have more than three memory segments active in >the OS at one time. > >Here's a snip of my current production system >--------------------------------------------------------------------------- - >------------ >noahsark:/home/dvp/mis_95/sql> onstat -g seg > > > >Informix Dynamic Server Version 7.30.UC7 -- On-Line -- Up 2 days 12:40:39 >-- 437240 Kbytes > > > >Segment Summary: > >id key addr size ovhd class blkused blkfree > >6 1381451777 c1461000 347062272 7744 R 42359 7 > >(shared) 1381451777 d5f5d000 100671488 2148 V 7299 4990 > >7 1381451778 dbf5f000 2777088 652 M 333 6 > >8 1381451779 dc205000 2777088 652 M 331 8 > >Total: - - 453287936 - - 50322 5011 > > > > (* segment locked in memory) > > > >noahsark:/home/dvp/mis_95/sql> ipcs -m | grep informix > >m 6 0x52574801 --rw-rw---- root informix > >m 7 0x52574802 --rw-rw-rw- root informix > >m 8 0x52574803 --rw-rw-rw- root informix > > > >There are only three segments active in the OS: ids 6, 7, and 8. 6 >corresponds to the resident and virtual memory segments for Informix, while >7 and 8 correspond to the Informix message queues. When Informix allocates >another segment of virtual memory, it allocates it as a separate segment to >the OS as well. In HPUX, when that fourth segment is allocated, you can get >some performance hits. > >If possible, use onmode -F to free unused memory segments. > >John Carlson >Informix DBA >EDS - WHSmith USA >3200 Windy Hill Road, Suite 1500 West >Atlanta, GA 30330 > > > > >> -----Original Message----- >> From: Colleen M. Morrow [mailto:cmmorrow@JonesDay.com] >> Sent: Tuesday, October 03, 2000 10:35 AM >> To: informix-list@iiug.org >> Subject: Slow performance after shmem dynamically allocated >> >> >> >> _______________________________________________________________ >> >> This message and any attachments are intended for the >> individual or entity >> named above. If you are not the intended recipient, please >> do not read, >> copy, use or disclose this communication to others; also >> please notify the >> sender by replying to this message, and then delete it from >> your system. >> Thank you. >> _______________________________________________________________ >> >> I've heard that there was a bug in previous versions of IDS that >> performance suffered after a new Virtual Memory segment was >> dynamically >> allocated. We're using 7.31.UC6 on HP 10.20. Does anyone know of any >> problems with that in this version? TIA. >> >> BTW, please respond directly to this address, thanks. >> >> Colleen >>