On 11/9/12 6:34 PM, Eitan Adler wrote:
On 9 November 2012 21:08, Alfred Perlstein <alf...@freebsd.org> wrote:
Modified: head/sys/kern/subr_param.c
+#ifdef VM_MAX_AUTOTUNE_MAXUSERS
+ if (maxusers > VM_MAX_AUTOTUNE_MAXUSERS)
+ maxusers = VM_MAX_AUTOTUNE_MAXUSERS;
+#endif
+ /*
+ * Scales down the function in which maxusers grows once
+ * we hit 384.
+ */
+ if (maxusers > 384)
+ maxusers = 384 + ((maxusers - 384) / 8);
+ }
Hey,
I know you didn't introduce this magic number 384. But can you (or
someone else) explain where it came from?
Sure, this is magic for i386 PAE machines. 384 maxusers was pretty much
the highest you wanted auto-tuned SAFELY for 32bit KVA on i386.
Now with 64 bit machines doing away with this hard ceiling, I wanted to
change the slope so that it doesn't grow too much as a conservative
measure to test the waters.
Take for example my amd64 machine with 16GB of ram.
Without the scaling factor of "maxusers = 384 + ((maxusers - 384) / 8)"
then I get 8173 maxusers.
8173 maxusers translates to 524096 nmbclusters (1024 + 8173 * 64).
That is 2GB RAM for just nmbclusters, nevermind jumbo9 and jumbo16.
With the scaling adjustment I get 1357 maxusers which is 87872 nmbclusters.
That is 343MB. Somewhat more reasonable.
I'm open to other suggestions and people coming in here to open the
value up higher... however I wanted a conservative value for now to
avoid too much concern.
We'll see where this takes us.
-Alfred
With this patch I get 75104 nmbclusters, which is 75104 pages which is
293 MB of ram!
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