Date: Fri, 25 Jun 1999 13:27:49 -0700 (PDT) From: Julian Elischer <julian@whistle.com> To: Alan Cox <alc@cs.rice.edu> Cc: Luoqi Chen <luoqi@watermarkgroup.com>, dyson@iquest.net, smp@freebsd.org Subject: Re: Call to arms..-SMP Message-ID: <Pine.BSF.3.95.990625132540.4244B-100000@current1.whistle.com> In-Reply-To: <19990625135341.H2331@cs.rice.edu>
next in thread | previous in thread | raw e-mail | index | archive | help
So I don't really understand the _cpl stuff. in regards to _cml I guess that theoretically, the BSDI method (lazy treading) makes all that go away doesn't it?. On Fri, 25 Jun 1999, Alan Cox wrote: > On Fri, Jun 25, 1999 at 02:21:08PM -0400, Luoqi Chen wrote: > > > Here's a question: Try compiling a kernel "make -jN". I experienced > > > an immense slow-down. (I added a call to acquire the giant lock if I > > > didn't already hold it just before userret. So doreti needed to release > > > it in all cases anyway.) I concluded that the problem is related > > > to _cpl because the following changes produced the same slowdown: > > > > > > Index: src/sys/i386/i386/exception.s > > > =================================================================== > > > RCS file: /home/ncvs/src/sys/i386/i386/exception.s,v > > > retrieving revision 1.61 > > > diff -c -r1.61 exception.s > > > *** exception.s 1999/06/01 18:19:36 1.61 > > > --- exception.s 1999/06/25 05:54:03 > > > *************** > > > *** 269,275 **** > > > movl $7,TF_ERR(%esp) /* sizeof "lcall 7,0" */ > > > FAKE_MCOUNT(13*4(%esp)) > > > MPLOCKED incl _cnt+V_SYSCALL > > > - SYSCALL_LOCK > > > ECPL_LOCK > > > #ifdef CPL_AND_CML > > > movl $SWI_AST_MASK,_cml > > > --- 269,274 ---- > > > > Maybe not, -current is using the int0x80 syscall interface (altsyscall), > > not the old "lcall 7,0" interface you modified, you might want to remove > > ALTSYSCALL_LOCK and try again. > > > > This fixed the performance problem. I'm amazed that I didn't > deadlock before. > > _cpl still however makes me queasy. Does anyone know why > we're locking a 32-bit store that ought to be atomic > by its very nature? > > Alan > > To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-smp" in the body of the message
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?Pine.BSF.3.95.990625132540.4244B-100000>