On Mon, 19 Mar 2007 12:27:40 -0700
Randy Dunlap <randy.dunlap@xxxxxxxxxx> wrote:
+The default vfs_cache_divisor value is 100 (like percent). However, for
+extremely large systems where a value of vfs_cache_pressure of less than
+1 percent is desirable, using a larger vfs_cache_divisor enables this wanted
+characteristic.
The one-percent-granularity problem also applies to /proc/sys/vm/*dirty*
and possibly other things. So any fix we do should be applicable to those
as well.
And I'm not really sure how we should do this. I do think that we should
change the kernel so these knobs are internally higher-resolution. So, for
example, we switch all the logic so that instead of these variables
representing 1/100th, they instead represent 1/1000000th, for example.
Then, we change the top-level /proc handler to do the 1/100th <-> 1/1000000th
conversion. So the rest of the kernel doesn't have to know about it.
The we duplicate all the relevant /proc knobs:
cat /proc/sys/vm/dirty_ratio
30
cat /proc/sys/vm/hires-dirty_ratio/
300000
Or we do something else ;)