From owner-cvs-all Tue May 21 13:47:16 2002 Delivered-To: cvs-all@freebsd.org Received: from freefall.freebsd.org (freefall.FreeBSD.org [216.136.204.21]) by hub.freebsd.org (Postfix) with ESMTP id 848FB37B40C; Tue, 21 May 2002 13:47:11 -0700 (PDT) Received: (from jhb@localhost) by freefall.freebsd.org (8.11.6/8.11.6) id g4LKlBY50788; Tue, 21 May 2002 13:47:11 -0700 (PDT) (envelope-from jhb) Message-Id: <200205212047.g4LKlBY50788@freefall.freebsd.org> From: John Baldwin Date: Tue, 21 May 2002 13:47:11 -0700 (PDT) To: cvs-committers@FreeBSD.org, cvs-all@FreeBSD.org Subject: cvs commit: src/sys/conf NOTES options src/sys/kern kern_mutex.c X-FreeBSD-CVS-Branch: HEAD Sender: owner-cvs-all@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.ORG jhb 2002/05/21 13:47:11 PDT Modified files: sys/conf NOTES options sys/kern kern_mutex.c Log: Add code to make default mutexes adaptive if the ADAPTIVE_MUTEXES kernel option is used (not on by default). - In the case of trying to lock a mutex, if the MTX_CONTESTED flag is set, then we can safely read the thread pointer from the mtx_lock member while holding sched_lock. We then examine the thread to see if it is currently executing on another CPU. If it is, then we keep looping instead of blocking. - In the case of trying to unlock a mutex, it is now possible for a mutex to have MTX_CONTESTED set in mtx_lock but to not have any threads actually blocked on it, so we need to handle that case. In that case, we just release the lock as if MTX_CONTESTED was not set and return. - We do not adaptively spin on Giant as Giant is held for long times and it slows SMP systems down to a crawl (it was taking several minutes, like 5-10 or so for my test alpha and sparc64 SMP boxes to boot up when they adaptively spinned on Giant). - We only compile in the code to do this for SMP kernels, it doesn't make sense for UP kernels. Tested on: i386, alpha, sparc64 Revision Changes Path 1.1033 +5 -0 src/sys/conf/NOTES 1.318 +1 -0 src/sys/conf/options 1.92 +26 -0 src/sys/kern/kern_mutex.c To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe cvs-all" in the body of the message