svn commit: r326758 - in head/sys/i386: conf include

[Conrad Meyer]

Author: cem
Date: Mon Dec 11 04:32:37 2017
New Revision: 326758
URL: https://svnweb.freebsd.org/changeset/base/326758

Log:
  i386: Bump KSTACK_PAGES default to match amd64
  
  Logically, extend r286288 to cover all threads, by default.
  
  The world has largely moved on from i386.  Most FreeBSD users and developers
  test on amd64 hardware.  For better or worse, we have written a non-trivial
  amount of kernel code that relies on stacks larger than 8 kB, and it "just
  works" on amd64, so there has been little incentive to shrink it.
  
  amd64 had its KSTACK_PAGES bumped to 4 back in Peter's initial AMD64 commit,
  r114349, in 2003.  Since that time, i386 has limped along on a stack half
  the size.  We've even observed the stack overflows years ago, but neglected
  to fix the issue; see the 20121223 and 20150728 entries in UPDATING.
  
  If anyone is concerned with this change, I suggest they configure their
  AMD64 kernels with KSTACK_PAGES 2 and fix the fallout there first.  Eugene
  has identified a list of high stack usage functions in the first PR below.
  
  PR:		219476, 224218
  Reported by:	eugen@, Shreesh Holla <hshreesh AT yahoo.com>
  Relnotes:	maybe
  Sponsored by:	Dell EMC Isilon

Modified:
  head/sys/i386/conf/NOTES
  head/sys/i386/include/param.h

Modified: head/sys/i386/conf/NOTES
==============================================================================
--- head/sys/i386/conf/NOTES	Mon Dec 11 02:44:15 2017	(r326757)
+++ head/sys/i386/conf/NOTES	Mon Dec 11 04:32:37 2017	(r326758)
@@ -968,7 +968,7 @@ device		ndis
 # KSTACK_PAGES is the number of memory pages to assign to the kernel
 # stack of each thread.
 
-options 	KSTACK_PAGES=3
+options 	KSTACK_PAGES=5
 
 # Enable detailed accounting by the PV entry allocator.
 

Modified: head/sys/i386/include/param.h
==============================================================================
--- head/sys/i386/include/param.h	Mon Dec 11 02:44:15 2017	(r326757)
+++ head/sys/i386/include/param.h	Mon Dec 11 04:32:37 2017	(r326758)
@@ -113,7 +113,7 @@
 #define IOPAGES	2		/* pages of i/o permission bitmap */
 
 #ifndef KSTACK_PAGES
-#define KSTACK_PAGES 2		/* Includes pcb! */
+#define KSTACK_PAGES 4		/* Includes pcb! */
 #endif
 #define KSTACK_GUARD_PAGES 1	/* pages of kstack guard; 0 disables */
 #if KSTACK_PAGES < 4