Re: Testing 7.0 Beta: FFS still very slow when creating files

[Taylor R Campbell <riastradh%NetBSD.org@localhost>]

   Date: Sun, 24 Aug 2014 15:26:46 +0200
   From: Stephan <stephanwib%googlemail.com@localhost>

   Okay maybe I should wait for dtrace to be enabled and working by default.

Well, plugh.  Every one of the instructions I rattled off from memory
was slightly wrong, and apparently the default amd64 kernel doesn't
have enough KVA reserved to even load the dtrace modules.  Here are
the right instructions:

https://wiki.netbsd.org/tutorials/how_to_enable_and_run_dtrace/

And NKL2_KIMG_ENTRIES has to be bumped from 16 to 32 in
sys/arch/amd64/include/pmap.h for the kernel to have enough KVA to
load the modules -- something we definitely ought to fix pronto.

   As I said, I could´t even enter ddb. Otherwise I could have placed a
   breakpoint on mutex_enter() to get example stack traces. I wonder,
   though, if this really can be related to locking as this test is
   basically single-threaded.

Could be, but I seem to recall we already isolated another
vcache-related performance problem to excessive lock/unlock cycles in
a single-threaded test.