Re: shared_buffer setting

Hi Km,

The shmmax setting is in *BYTES*.

Regards
Talha Khan

On 10/6/06, Talha Khan <talha(dot)amjad(at)gmail(dot)com> wrote:
>
> Hi Km,
>
> The shmmax setting is in bits.
>
> For knowing the details about the shared_buffer settings and
> other configuration features follow the link given below:
>
> http://www.powerpostgresql.com/PerfList
>
> The shmmax value set in your kernel (i.e 33554432) seems quite low seeng
> that you have 8GB physical RAM. Yes! you can set shmmax to half of your RAM
> but it all depends upon how you use your system .I would recommend setting
> it to 2/3 of your RAM.You can set the value in sysctl.conf file. and then
> reflect the setting by using sysctl -p switch.
>
> Regards
> Talha Khan
>
>
> On 10/6/06, km <km(at)mrna(dot)tn(dot)nic(dot)in> wrote:
> >
> >
> > Hi all,
> > Iam using postgresql 8.1.4 with 8GB physical RAM.
> >
> > OS kernel max shared memory usage is set to( /proc/sys/kernel/shmmax)
> > 33554432
> > dont know if this number is in bytes or bits
> > now how do i set my shared_buffer setting in postgresql.conf such that
> > ican use max shared memory setting of the kernel.
> >
> > also default shared_buffer setting is 1000 - its not clear if i have to
> > multiply this number with 8KB to be <= max shared memory value or it is 1000
> > bytes or bits.
> > can i set the max shared memory value to use atleast half of my physicl
> > RAM available ?
> > any idea ?
> > also i would like to know how is the performance hit when we change
> > shared_buffer value in general ?
> >
> > regards,
> > KM
> >
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