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Provide a streamlined '#define curthread __curthread()' for amd64 to avoid

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the compiler having to parse and optimize the PCPU_GET(curthread) so often.
__curthread() is an inline optimized version of PCPU_GET(curthread) that
knows that pc_curthread is at offset zero in the pcpu struct.  Add a
CTASSERT() to catch any possible changes to this.  This accounts for
just over a 1% wall clock speedup for total kernel compile/link time,
and 20% compile time speedup on some specific files depending on which
compile options are used.

Approved by:  re (jhb)
This commit is contained in:
Peter Wemm 2003-11-20 22:54:44 +00:00
parent de8e370ec1
commit 5dd883833c
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=122930
2 changed files with 13 additions and 0 deletions
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3
sys/amd64/amd64/machdep.c
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@ -121,6 +121,9 @@ __FBSDID("$FreeBSD$");
#include <sys/ptrace.h>
#include <machine/sigframe.h>
/* Sanity check for __curthread() */
CTASSERT(offsetof(struct pcpu, pc_curthread) == 0);
extern u_int64_t hammer_time(u_int64_t, u_int64_t);
extern void dblfault_handler(void);

10
sys/amd64/include/pcpu.h
View file

@ -159,6 +159,16 @@ extern struct pcpu *pcpup;
#define PCPU_PTR(member) __PCPU_PTR(pc_ ## member)
#define PCPU_SET(member, val) __PCPU_SET(pc_ ## member, val)
static __inline struct thread *
__curthread(void)
{
struct thread *td;
__asm __volatile("movq %%gs:0,%0" : "=r" (td));
return (td);
}
#define Xurthread (__curthread())
#else
#error gcc or lint is required to use this file
#endif