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On Thu, Nov 12, 2009 at 12:10 AM, Sam Jas <samja...@yahoo.com> wrote:
>
> Hi,
>
> We are facing issue with the RES memory. Below is the o/p of top command. It 
> shows that writer process reserved 3.8g. We have observed that if it 
> increased to 3.9g we need to restart the db. Otherwise it hangs.  Kindly 
> suggest us the good way to figure it out this issue.   shared_buffer is 3 GB.

Are you sure this is what your problem really is?  It's quite normal
for the bgwriter to show a high res / shr number because it touches
all the shared_buffers eventually.  On my main db at work, where we
have 8G shared_buffers, it looks like this:

  PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND
32284 postgres  15   0 8446m 7.5g 7.5g S  0.0 23.8   2:35.10 postgres:
writer process
  337 postgres  15   0 8475m 7.0g 7.0g S  0.0 22.2 116:15.04 postgres:
slony www 10.0.0.104(56186) idle
  336 postgres  16   0 8455m 4.7g 4.7g S  4.1 14.8 148:57.29 postgres:
slony www 10.0.0.104(56184) COMMIT
  335 postgres  18   0 8457m 3.9g 3.9g S  0.0 12.5 598:04.23 postgres:
slony www 10.0.0.104(56183) idle

Note that the amount of memory used by a process on its own is
RES-SHR, so that none of these processes are actually using 7.5, 7.0,
4.7 or 3.9 Gigs by themselves.

> PID       USER      PR  NI  VIRT   RES  SHR S %CPU %MEM    TIME+  COMMAND
>
>  4822 postgres  15   0 4045m 3.8g 3.8g S  0.7 12.1   2:09.63 postgres: writer 
> process

Generally this isn't a problem.  Is this 100% reproduce-able?  Are you
sure there's no other problem, or that maybe a checkpoint kicks in at
the same time and your "hung" database isn't just unresponsive for a
minute or so?

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