Le 22 nov. 2009 à 15:35, Simon a écrit :
> Hi Nicolas,
>
> Thank you.
>
> I think adding extra swap device would not be helpful in our case,because the
> customer appliction created too many stack/heaps,these anonymous memory has
> to use swap device as back store,if the physical RAM really shortage,more
> swap device only cause page out cost and performance will be degraded
> accordingly,right ?
Right. Except in one case....DISM use of shared memory.
Take a look to this command :
> # ipcs -ZAm | awk 'NR>1&&$16>0{s+=$10} END{print "total=", s/1024}'
If there's something different than 0, your Sybase is using DISM segments.
With DISM, there's a double 'reservation'....one at creation time, and another
at attach time. 'Reservation' doesn't mean 'utilisation', the only way to have
sufficient 'rerservation' space is to add swap. Nothing will be swapped out
because it's only a reservation. It's just a security to be able to swap out
theses segments in case of DR.
Nicolas
>
>
> Thanks.
> Best Regards,
> Simon
>
>
> On Sat, Nov 21, 2009 at 8:01 PM, Nicolas Dorfsman <n...@woup.net> wrote:
>
> Hi Simon,
>
> Le 21 nov. 09 à 07:27, Simon a écrit :
>
>
> # ipcs -a
> IPC status from <running system> as of Thu Nov 12 12:05:28 HKT 2009
> T ID KEY MODE OWNER GROUP CREATOR CGROUP
> CBYTES QNUM QBYTES LSPID LRPID STIME RTIME CTIME
> Message Queues:
> T ID KEY MODE OWNER GROUP CREATOR CGROUP
> NATTCH SEGSZ CPID LPID ATIME DTIME CTIME
> Shared Memory:
> m 3 0xe9032d40 --rw------- sybase staff sybase staff
> 3 738803712 1314 2125 20:47:22 no-entry 20:47:14
> m 2 0x51 --rw-rw-r-- root root root root
> 1 2000196 2122 8553 15:15:18 15:15:23 13:14:38
> m 1 0x50 --rw-rw-r-- root root root root
> 1 600196 2121 2121 13:14:38 no-entry 13:14:38
> m 0 0xe9032d32 --rw------- sybase staff sybase staff
> 3 7851147264 1314 2125 13:14:40 13:14:40 13:13:42
> T ID KEY MODE OWNER GROUP CREATOR CGROUP
> NSEMS OTIME CTIME
> Semaphores:
> s 1 0x51 --ra-ra-ra- root root root root
> 6 12:05:28 13:14:38
> s 0 0x50 --ra-ra-ra- root root root root
> 6 12:05:28 13:14:38
>
> I'm not sure about Sybase and ISM/DISM, but you may take a look to
> ISM/DISM segments by :
>
> # ipcs -ZAm | awk 'NR>1&&$16>0{s+=$10} END{print "total=", s/1024}'
>
> DISM segments may suffer of double allocation algorithm. The Workaround is
> to add as many disk-swap-area as your SGBD SHM reservation.
> I've wrote an article on that
> (http://www.solaris-fr.org/home/docs/base/memoire), but in french for now,
> sorry.
>
> Nicolas
>
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