Author: mjg
Date: Sat Feb 17 00:23:28 2018
New Revision: 329420
URL: https://svnweb.freebsd.org/changeset/base/329420
Log:
Postpone sx_sunlock(&proctree_lock) on fork until after allproc is dropped.
There is a significant contention on the lock during -j 128 package build.
This change drops total wait time on this lock by 60%.
Modified:
head/sys/kern/kern_fork.c
Modified: head/sys/kern/kern_fork.c
==============================================================================
--- head/sys/kern/kern_fork.c Sat Feb 17 00:21:50 2018 (r329419)
+++ head/sys/kern/kern_fork.c Sat Feb 17 00:23:28 2018 (r329420)
@@ -401,8 +401,6 @@ do_fork(struct thread *td, struct fork_req *fr, struct
trypid = fork_findpid(fr->fr_flags);
- sx_sunlock(&proctree_lock);
-
p2->p_state = PRS_NEW; /* protect against others */
p2->p_pid = trypid;
AUDIT_ARG_PID(p2->p_pid);
@@ -414,6 +412,7 @@ do_fork(struct thread *td, struct fork_req *fr, struct
PROC_LOCK(p1);
sx_xunlock(&allproc_lock);
+ sx_sunlock(&proctree_lock);
bcopy(&p1->p_startcopy, &p2->p_startcopy,
__rangeof(struct proc, p_startcopy, p_endcopy));
@@ -977,8 +976,8 @@ fork1(struct thread *td, struct fork_req *fr)
}
error = EAGAIN;
- sx_sunlock(&proctree_lock);
sx_xunlock(&allproc_lock);
+ sx_sunlock(&proctree_lock);
#ifdef MAC
mac_proc_destroy(newproc);
#endif
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