Date: Tue, 11 Nov 2003 14:07:30 -0800 (PST) From: John Baldwin <jhb@FreeBSD.org> To: src-committers@FreeBSD.org, cvs-src@FreeBSD.org, cvs-all@FreeBSD.org Subject: cvs commit: src/sys/conf files src/sys/kern kern_mutex.c kern_thread.c subr_turnstile.c subr_witness.c src/sys/sys _mutex.h filedesc.h proc.h Message-ID: <200311112207.hABM7UAu006144@repoman.freebsd.org>
next in thread | raw e-mail | index | archive | help
jhb 2003/11/11 14:07:30 PST
FreeBSD src repository
Modified files:
sys/conf files
sys/kern kern_mutex.c kern_thread.c
subr_turnstile.c subr_witness.c
sys/sys _mutex.h filedesc.h proc.h
Log:
Add an implementation of turnstiles and change the sleep mutex code to use
turnstiles to implement blocking isntead of implementing a thread queue
directly. These turnstiles are somewhat similar to those used in Solaris 7
as described in Solaris Internals but are also different.
Turnstiles do not come out of a fixed-sized pool. Rather, each thread is
assigned a turnstile when it is created that it frees when it is destroyed.
When a thread blocks on a lock, it donates its turnstile to that lock to
serve as queue of blocked threads. The queue associated with a given lock
is found by a lookup in a simple hash table. The turnstile itself is
protected by a lock associated with its entry in the hash table. This
means that sched_lock is no longer needed to contest on a mutex. Instead,
sched_lock is only used when manipulating run queues or thread priorities.
Turnstiles also implement priority propagation inherently.
Currently turnstiles only support mutexes. Eventually, however, turnstiles
may grow two queue's to support a non-sleepable reader/writer lock
implementation. For more details, see the comments in sys/turnstile.h and
kern/subr_turnstile.c.
The two primary advantages from the turnstile code include: 1) the size
of struct mutex shrinks by four pointers as it no longer stores the
thread queue linkages directly, and 2) less contention on sched_lock in
SMP systems including the ability for multiple CPUs to contend on different
locks simultaneously (not that this last detail is necessarily that much of
a big win). Note that 1) means that this commit is a kernel ABI breaker,
so don't mix old modules with a new kernel and vice versa.
Tested on: i386 SMP, sparc64 SMP, alpha SMP
Revision Changes Path
1.848 +1 -0 src/sys/conf/files
1.132 +39 -225 src/sys/kern/kern_mutex.c
1.162 +3 -0 src/sys/kern/kern_thread.c
1.132 +471 -758 src/sys/kern/subr_turnstile.c
1.162 +3 -3 src/sys/kern/subr_witness.c
1.10 +0 -2 src/sys/sys/_mutex.h
1.52 +2 -0 src/sys/sys/filedesc.h
1.357 +8 -4 src/sys/sys/proc.h
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?200311112207.hABM7UAu006144>