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i386: Bump KSTACK_PAGES default to match amd64

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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
This commit is contained in:
Conrad Meyer 2017-12-11 04:32:37 +00:00
parent 14382fcf29
commit 3f6867ef63
2 changed files with 2 additions and 2 deletions
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2
sys/i386/conf/NOTES
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@ -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.

2
sys/i386/include/param.h
View File

@ -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