Date: Wed, 10 Nov 2004 22:00:05 -0800 From: Julian Elischer <julian@elischer.org> To: Scott Long <scottl@freebsd.org> Cc: David Schultz <das@freebsd.org> Subject: Re: U Area Removal Message-ID: <4192FFE5.8060205@elischer.org> In-Reply-To: <4192D9AB.5060309@freebsd.org> References: <20041111030035.GA70923@VARK.MIT.EDU> <4192D9AB.5060309@freebsd.org>
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Scott Long wrote: > David Schultz wrote: > >> Over the years, the amount of data we have stored in each process' U >> area has eroded to the point where all we have left are the following: >> >> - A struct kinfo_proc that is only used for a.out core dumps. >> This can be reconstructed at the time of the core dump, so >> it doesn't need to be there. >> >> - The struct pstats for the process, which takes a mere 216 bytes >> on i386. >> >> In exchange for the ability to swap out this 216-byte structure, we >> keep around a 4096-byte page, a 132-byte vm_object, and a couple of >> pointers. Moreover, there is a small amount of runtime overhead >> associated with this, and developers need to remember to PHOLD() and >> PRELE() the process as appropriate.[1] >> >> I propose to remove the ability to swap the U area, allocating p_stats >> from malloced memory instead. Medium-term scheduling and swapping of >> kernel stacks would be retained. Here are the patches; !i386 testers >> wanted: >> >> http://www.freebsd.org/~das/patches/upages.diff >> >> >> [1] Most of the instances of PHOLD() and PRELE() right now never >> needed to be there or have been unnecessary ever since the PCB >> was moved out of the U area. > We've been slowly working towards this.. when we moved the pcb out to the thread this became inevitable.. go for it! > > Go for it! Just get some validation that amd64 and sparc64 work, and > then do the deed. I'll try testing at least amd64 right now. > > Scott > _______________________________________________ > freebsd-arch@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-arch > To unsubscribe, send any mail to "freebsd-arch-unsubscribe@freebsd.org"
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