On 4/23/2012 9:28 PM, Gustavo R Leal wrote:
I believe I've found the solution to excessive swapping with 1GB of memory.There is a script "/usr/lib/pm-utils/power.d/laptop-mode" that is setting too low values to VM tunable kernel parameters when on AC power: dirty_background_ratio=5 dirty_ratio=10 The line 69 of the script is the following: write_values 0 10 5 500 Changing the line with these values resulted in being able to run the system with 1GB without swap partition and good performance even with many large processes running. write_values 0 90 20 500 This sets the VM subsystem with these values: dirty_background_ratio=20 dirty_ratio=90
That makes the dirty_ratio even higher than when on battery. The purpose of tuning these is to allow a laptop on battery to be more aggressive about keeping dirty pages in the cache and letting the disk stay asleep. Normally you want dirty pages to be flushed to disk fairly quickly.
I'm curious if the normal value of 5 for background ratio but just increasing dirty_ratio to 20 or 25 would have a similar effect on your performance trouble without going to an excess.
Also if anything, increasing dirty_ratio should make swapping worse, not better, since more ram will be tied up in dirty cache pages. Are you sure you have a problem with swapping and not just applications blocking while writing data to disk?
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