[LON-CAPA-admin] memory and httpd processes

[Todd Ruskell]

Jim,

This doesn't surprise me too much.  One thing about top is that the reported 
amount of memory used includes all kinds of cached data that isn't really 
"used" in the sense that it contains crucial code for a currently running 
process.  It is only "used" in the sense that it contains a bunch of data 
that was accessed recently, and some process decided it might improve 
response times if this data were kept in memory rather than always going out 
to disk, for example.  I haven't checked my servers regularly, but on my 
desktop machines, top nearly always reports I am at full memory use, even 
though I know the currently loaded programs aren't that big.  My guess is 
that when you stop httpd, it intelligently tells the kernel to *really* let 
that memory go.

As to why this drastically improves performance, I will let those with much 
more knowledge answer that question more intelligently than I can.

Todd

On Wednesday 04 May 2005 08:58 pm, Jim Maxka wrote:
> Hi all -- I just want to run this by people to see how crazy I am.  I
> have one access server and a library server, each with 2 GB of physical
> memory.  During high usage times, top shows all of the memory used.  If
> I run, /etc/init.d/httpd reload I can recover up to 500 MB, sometimes
> more.  Performance for users seems to improve.  I tested it with users,
> when they reported lag times when hitting submits and refresh of
> variables passed to applications -- like the jme editor.
>
> Here is an example:
> #####before reload
> Mem:   2074928k total,  1990800k used,    84128k free,   351024k buffers
> Swap:  2337416k total,      224k used,  2337192k free,   960936k cached
> [root at loncapa jmol]# /etc/init.d/httpd reload
> Reloading httpd:                                           [  OK  ]
> ####after reload
> Mem:   2074928k total,  1598448k used,   476480k free,   343740k buffers
> Swap:  2337416k total,      224k used,  2337192k free,   797400k cached
>
> Right now I do this manually, but I was wondering if it would be worth
> writing a cron job to do this more often.  Or am I completely making
> something up here?  thanks -- jim
> _______________________________________________
> LON-CAPA-admin mailing list
> LON-CAPA-admin at mail.lon-capa.org
> http://mail.lon-capa.org/mailman/listinfo/lon-capa-admin