Date: Mon, 29 Oct 2007 23:06:50 +0100 From: Kris Kennaway <kris@FreeBSD.org> To: Daniel Eischen <deischen@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: <4726597A.6000004@FreeBSD.org> In-Reply-To: <Pine.GSO.4.64.0710291756360.19572@sea.ntplx.net> 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>
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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? Kris
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