Date: Mon, 29 Oct 2007 18:11:29 -0400 (EDT) From: Daniel Eischen <deischen@freebsd.org> To: Kris Kennaway <kris@freebsd.org> Cc: cvs-src@freebsd.org, src-committers@freebsd.org, cvs-all@freebsd.org Subject: Re: cvs commit: src/lib/libthr/thread thr_mutex.c src/lib/libkse/thread thr_mutex.c src/include pthread.h Message-ID: <Pine.GSO.4.64.0710291808160.19572@sea.ntplx.net> In-Reply-To: <4726597A.6000004@FreeBSD.org> References: <200710292101.l9TL1mAE049561@repoman.freebsd.org> <Pine.GSO.4.64.0710291712100.19572@sea.ntplx.net> <472650BF.5060706@FreeBSD.org> <Pine.GSO.4.64.0710291732090.19572@sea.ntplx.net> <4726560F.5050804@FreeBSD.org> <Pine.GSO.4.64.0710291756360.19572@sea.ntplx.net> <4726597A.6000004@FreeBSD.org>
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On Mon, 29 Oct 2007, Kris Kennaway wrote: > Daniel Eischen wrote: >> On Mon, 29 Oct 2007, Kris Kennaway wrote: >> >>> Daniel Eischen wrote: >>>> On Mon, 29 Oct 2007, Kris Kennaway wrote: >>>> >>>>> Daniel Eischen wrote: >>>>>> >>>>>> The libkse implementation already spins for a bit. The default >>>>>> number of spins is 500. >>>>> >>>>> OK, cool. >>>>> >>>>>> I'm not sure that another mutex type is warranted, the default >>>>>> mutex implementation should be adaptive I think. >>>>> >>>>> The point being that certain existing applications already know about >>>>> this mutex name and will use it automatically when it exists. >>>>> >>>>> I am a bit wary of making this the default type though. The algorithm >>>>> is a pessimization when the conditions described above are not true. >>>> >>>> I agree, and it applies a little to the KSE approach also. >>>> Spinning is mostly a hack for not being able to tell in >>>> userland if a thread is swapped in/out or is on another >>>> CPU. If you solve that problem, then you can make the >>>> default mutex adaptive. >>> >>> Yeah. It looks like Solaris does this. In principle you could do it >>> cheaply with a shared page, I'm not sure what Solaris does. >> >> I think we should add back the thread mailbox for libthr threads. >> I was in favor of keeping the mailbox for libthr, and this might >> be a good use for it. > > I am not familiar with that code, can you point me to the change that removed > it? This was when David revised libthr, so it never really had a mailbox. libkse has the mailbox, and I would have preferred keeping a similar interface for libthr (specifying it on thr_create(2)). You can look at how it works for KSE as an example. -- DE
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