Messages in this thread |  | | From | "Gregg G. Wonderly" <> | Subject | Re: [ Matthias Sattler ] Bad 1.3.95 interactive performance (fwd) | Date | Mon, 29 Apr 1996 15:33:23 -0500 |
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In your message dated: Mon, 29 Apr 1996 20:39:41 +0200 >In addition to that, I'm a bit alarmed because no one else seems to see this >problem :-(
Well, looking at the output of free, it looks to me like you don't have enough physical memory for you set up. And, considering you seem to have a single disk, I am amazed (in a sense) that the disk head is not protruding from the side of your machine by now!
I am sure that most people on this list understand the concepts of swapping and paging. What some people might not understand are the issues with the use of VM, the number of partitions your disk(s) has/have and the disks that have swap space on them verses those that have swap and active text on them.
In recent times, it was decided that there was no reason to swap text (remember the sticky bit) because it was faster to just tell the VM manager that the memory for text was free and read it back from the original disk location later (text file busy scrolling up the screen...)
The problem is that by doing this, the disk I/O for an active system that is using VM to manage the address space(s) must now traverse a larger physical surface area to get the text for all the active programs and then go back to the swap partition to read/write data, than it did when it was all in one partition! So, when you have a single disk and swapping starts, you can bet that it could take quite some time to accomplish the VM shuffle required to handle all of the address spaces that are active.
My machine has 2 1GB scsi disks (CONNORs), and 1 2GB IDE disk (MAXTOR). The day that I moved all of my swap to the IDE, I decided I did not need more phsical memory. It used to take 10-15secs to switch virtual desktops in fvwm. Now it takes 2-3secs! And that it swaping from a file that is located on a fat file system.
It might be interesting to turn off the special case for text some day and see what happens to swapping when the head can hover over a single partition again!
Ever heard of a paging drum? If you know someone who has one of those really small SCSI or IDE drives (40-200 megs), you might think about picking one up and using it for your swap partition. It will at least keep the head from having to consistantly wander around between text and data sources during swapping. And maybe, like it did for me, you'll get a sizeable performance improvement without having to buy more physical RAM (which I think is the source of your wild swapping problem).
----- gregg@lucent.com (Gregg Wonderly)
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