Date: Mon, 29 Oct 2007 17:58:32 -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.4.64.0710291756360.19572@sea.ntplx.net> In-Reply-To: <4726560F.5050804@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>
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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: >>>> >>>> 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. -- DE
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