Date: Thu, 03 Aug 1995 21:28:55 -0700 From: David Greenman <davidg@Root.COM> To: jiho@sierra.net Cc: freebsd-questions@freefall.cdrom.com Subject: Re: 2.0.5 Eager to go into swap Message-ID: <199508040428.VAA13446@corbin.Root.COM> In-Reply-To: Your message of "Thu, 03 Aug 95 15:34:28 -0800." <199508032331.AA27711@diamond.sierra.net>
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>But those differences are small, and they still don't explain the horrendous >swapping generated by X, unless the decision to swap is totally blind to >page sharing, which makes no sense. It is escentially blind. The policy of which pages to reclaim is based on frequency of page usage, not on how many people have it mapped. Horrendous swapping? If that is true on machines with >=16MB of memory, then perhaps there is a problem...but that doesn't match my own experiance. >And don't FreeBSD and Linux pretty much use the same XFree86 libraries, >with the same ordering of contents? No. The way the shared libraries are built is completely different. I don't know if Linux orders their X libraries, but I have heard that they do order their system libraries (libc, etc). > It's supposed to be better with ELF, >but the older Linux library scheme was a mess, it required libraries to load >at fixed, bureaucratically-registered addresses. Having libraries at fixed addresses actually improves execution performance because the code need not be PIC (PIC consumes a register which is scarce on x86's). > I had more trouble running >out of swap with X under Linux than I've had under FreeBSD. That begs the question "Then why are you complaining?". :-) >About malloc(), whose and which malloc() are you talking about, and why >doesn't it "work right"? We use the Berkeley malloc by default which causes power of 2 allocations to allocate twice as much memory as is needed. It's a function of its design - it takes a few bytes more than it needs for the allocation, and the allocation buckets are power of 2. So a request for a power of 2 amount causes the allocation to fall into the next bucket (which is twice as large). >This all seems to be degenerating into a useless flap without addressing >the original issue much. > >I remember reading a gripe column in BYTE, where a networking support >guy at Cray was complaining because customers wanted to run X on >laptops and he couldn't do it for them. He recalled a time when X ran fine >on Suns with 4 MB of RAM. Now we have a user who likes FreeBSD >because it runs X fine with 16 MB (although others dispute that even with >32 MB). I don't see where the basic server (extensions aside) has acquired >much new functionality to account for the difference. It's just quadrupled >in size and extrapolated its RAM requirements. > >Maybe that's why nobody wants to deal with this issue--it collapses into a >flame war and nobody can do anything about it anyway! There are different levels of "fine"ness. I had a VAXstation-2000 here for awhile. It runs a version of X11R3...and has only 6MB of RAM. It is absolutely DOG slow...and not because the CPU is slow, but because it thrashes constantly. Using it was an absolute pain. Similarly, a MicroVAX with 16MB of memory also paged a little when running X - especially once you start using things like gcc which is a complete memory pig (needing >3MB of memory). -DG
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