Hi ,
As far as i know, inactive_dirty pages are types of virtual memory pages
which muste be written to disk before reuse. This means , if an
application needs memory and if the operatimg system decides or has to
use a page that is inactive_dirty , the data inside this memory must be
written to disk. ( Here by saying disk , i mean swap disk for anon pages
, and normal data files for file caches. )
This is what i know , i will be appreciated if some one also corrects my
points. The file caching issue is also what i especially wonder.
Anyway , lets return to inactive_dirty issue. Here what my box showes:
[oracle@tanidw1 proc]$ cat meminfo
total: used: free: shared: buffers: cached:
Mem: 8490827776 7332200448 1158627328 0 376569856 3980132352
Swap: 25165725696 589660160 24576065536
MemTotal: 8291824 kB
MemFree: 1131472 kB
MemShared: 0 kB
Buffers: 367744 kB
Cached: 3853888 kB
SwapCached: 32960 kB
Active: 2433184 kB
Inact_dirty: 2035712 kB
Inact_clean: 282592 kB
Inact_target: 950288 kB
HighTotal: 0 kB
HighFree: 0 kB
LowTotal: 8291824 kB
LowFree: 1131472 kB
SwapTotal: 24575904 kB
SwapFree: 24000064 kB
Committed_AS: 97331872 kB
HugePages_Total: 0
HugePages_Free: 0
Hugepagesize: 262144 kB
[oracle@tanidw1 proc]$ free
total used free shared buffers
cached
Mem: 8291824 7160352 1131472 0 367760
3853904
-/+ buffers/cache: 2938688 5353136
Swap: 24575904 575840 24000064
inactvi_dirty value is 2035712 , lets say 2GB. My free ram is 5353136.
Right now the server is not loaded.
This inactive_dirty pages can be reused , if necessary . The os decides
to launder enough pages in order to keep up with the memory pressure.
When the memory pressure increases , what i observerse is
inactive_dirty pages are not laundered fast enough , and sar -W shows
swapping activity , sar -B shows page outs. What i do periodically is
to force the os to launder inactive dirty pages . ( I do this with a
simple c program which allocates lots of memory , touches each of them .
Only allocating memory is not enough due to the reservation-committing
issues of virtual memory)
Kind Regards
Tolga
-----Original Message-----
From: redhat-list-bounces@xxxxxxxxxx
[mailto:redhat-list-bounces@xxxxxxxxxx] On Behalf Of mac subbu
Sent: Monday, March 06, 2006 7:23 AM
To: General Red Hat Linux discussion list
Subject: Re: Red HAT AS3 memory issues
Hi,
Thanks for the suggestion...could you let us know the significance of
inact_dirty pages
/proc/meminfo and inact_dirty pages to get detailed memory usage
IF inact_dirty pages is low does it mean my system is optimally using
RAm
and may be coming under pressure ??
Thnaks and regards
On 3/6/06, Tolga Evren <tolgae@xxxxxxxxxxx> wrote:
>
> Hi,
>
> This is normal behaviour. Linux tries to use all available memory as
> cache. Whenever free memory is
> needed ,the os uses the memory which is reported as free .
>
> try to use :
>
> sar -B to see whether page-in or out is happening
>
> sar -W to see swapping activity
>
> /proc/meminfo and inact_dirty pages to get detailed memory usage
>
> sar -r : to see swap , cache usage.
>
> Regards,
> tolga
>
>
>
> ________________________________
>
> From: redhat-list-bounces@xxxxxxxxxx on behalf of mac subbu
> Sent: Sun 3/5/2006 3:48 AM
> To: redhat-list@xxxxxxxxxx
> Subject: Red HAT AS3 memory issues
>
>
>
> HI,
>
> We have a linux AS3 on a server with 4 GB RAM
>
> At any point of time my Free -m Gives total of 4000 mb and used of
3900
> and free 10 mb but my buffers/cache used is hardly 1000 mb and 3000
mb
> free
>
> Whereas
>
> the top always gives
>
> mem used 4000 mb avg and used 3972
>
> Going by bufffers/cache i shudnt be having memory issues BUT our
server is
> monitored and keeps throwing above 80% memory utilisation all the time
>
>
> why is there a discrepancy between TOP and FREE and which shud be used
> more definitely for memory analysis
>
> and why do we get over 80% used all the time when buffers/cache is low
all
> times
>
> Any pointers would be appreciated
>
> regards
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