Re: Hibernation
On Fri, 19 Nov 1999, Heather wrote:
>> So you create a 1M partition for swap then. Using RAM as swap will not gain
>> you anything. At best it won't be used and will just be a waste of memory
>> that could otherwise be used for disk cache. At worst you will have programs
>> being paged to it which means copying data to/from the memory area which
>> wastes CPU time.
>
>If it's there it will be used. Therefore during system operations the disk
>will be hit. If you are so insanely sensitive that you can "feel" the diff
>between hitting disk and hitting RAM - notice I haven't said I'm using the
>trick - then your measly scrap of swap could be on... more RAM. There is
>probably even some optimal size for the silly thing.
The point is that a scrap of swap in ram decreases main memory and makes the
swap more likely to be used.
>> With 64bit memory it will take 512 reads and 512 writes to copy a 4K page of
>> memory. If the memory is 10ns then it'll be 10*1024 == 10240ns to copy the
>> page. That's 4096 clock cycles on a modern CPU.
>
>Not useful statistic without a similar analysis of how many cycles paging
>the same amount a disk takes - and straying off things that are specific to
>laptops, nor debian.
The issue is that it will be used directly if it's not forced to be in swap
because of main memory being used by a RAM disk (for swap).
>> Having slower CPUs also means that we need to conserve their power more too.
>> That means not using swap-to-RAM, putting plenty of RAM in the system (so the
>> CPU doesn't block on paging), and doing anything else reasonable to get
>> effective use of CPU power.
>
>hard disk = motor = conserves lots to not have it spin, if you have an old
>enough monster. Betcha motors cost more than bit flips.
Yes. However any program that gets swapped out will have it's code pages
discarded. So when it starts to be used again the code pages will have to be
brought in from disk and the drive will spin up anyway.
The only exception to this is certain types of binaries in the "a.out" family
which behaved like DOS .COM files (code and data in the same memory area).
>> Currently I am using the Xserver-fbdev which can't take advantage of the
>> co-processed features of my video card and wastes CPU power and energy.
>> I plan to write a Neomagic FrameBuffer driver and then try and get the
>> xserver-fbdev co-prossing patches going (they apparently work well on Power
>> Macintosh).
>
>Isn't Neomagic supported directly in the latest X? Why use a non-optimal
>server?
I always had big problems having two X servers running on the same display
before I went to fbdev. I have VT5 and VT6 running seperate X sessions.
>> What I would like to see is a laptop that supports multiple hard drives.
>> RAID-1 on desktop features is starting to become common (it will become
>> especially common when the Raidtools2 stuff gets into the mainstream kernel).
>> I think that we need the same in laptops. Also for more serious use they
>> should sell laptops with support for 4 hard drives to run RAID-10.
>
>I have an IDE adapter cable, and it's possible to get a SCSI one, but that
>wouldn't really do what you want. The Omnibook 800 - as far as I can tell
>unique among laptops - has its internal SCSI bus accessible as an external
>port, so you should be able to hang a whole chain off of it. Helluva docking
>station you get there :)
External SCSI requires power down to disconnect. Even with hibernation it
would be a PITA.
>If the focus of laptops is to be portable - what sort of task needs to
>carry a half-terabyte around with you *regularly*? Or are you looking for
>the parity/stability which RAID is supposed to offer - why wouldn't the
>upcoming journaling be enough? Just curious...
Journalling does not replace parity at all. In fact if anything journalling
probably increases the need because it'll be more difficult to recover from a
partial hardware failure!
What I wait is RAID-1 for reliability and double the read bandwidth. I also
want RAID-0 for bulk write bandwidth and for read performance when I have
many processes running. Combine that into RAID-10 and you need a minimum of
4 hard drives but get great performance.
I use my laptop as a development and test machine for ISP servers amoung
other things. Also I compile many largish programs.
I could use RAID-10 for LDAP ldif imports and performance while compiling
large programs. Lots of RAM will be handy for compiling MICO (gcc takes 160M
of memory) and for running OpenLDAP (wants database size * 1.5 amount of RAM
for good performane - I'm playing with a 40M database).
I use my laptop to compare Linux to UNIX servers that come from all the big
vendors and I like Linux to win. Recently I had the opportunity to replace a
Sun server with 400M of RAM and SCSI RAID with a PC running Linux (128M and
an IDE drive). The Linux machine is significantly faster, now I just want
RAID-1 on it for obvious reasons!
>On a different note there are 47 Gb SCSI drives running around now. That's
>a single drive for a desktop system, but ... it's a funny thing, if I could
>jump from 3.2 Gb to 26 or 47 Gb instead of merely 10 or 12, I think I'd be
>more seriously considering it! So I eagerly await if they can get them down
>to our size and power requirements. Obviously some people are willing to
>carry anything, given some of the monster notebooks coming out, so I'm not
>going to call weight a strong factor.
I want to carry <3Kg. I believe that 4 * 10G hard drives can fit into a 3Kg
laptop if it's correctly designed.
>> When you move to a journalled file system you may feel the need for more RAM.
>> Journalling does result in a larger working-set for the cache system...
>
>If I feel the need for more RAM than 96M I'll just plain be stuck, because
>it's maxed out.
No. Just buy a new laptop. I think that you should get a new one every 18
months.
>> I spend less money on laptops than most people spend on cars...
>
>That's good, very few laptops cost 32 k$. Though
Although I do spend more than many people spend on cars. ;)
><pipe dream>
>an 8.5-10 pound laptop with a half Gb of memory (expandable further) with
>2 internal, 1 swappable drive bays (options 10 Gb through 38 Gb in size)
>with [whatever the latest rage in perfected laptop monitors is] plus builtin
>CD/DVD capable, real stereo access, Video4Linux supported vidtuner graphics
>card,
></pipe dream>
>might start getting there.
Firstly you don't want to lug 5Kg. You want at most 3.5Kg with 1280x1024
display, 500M of RAM, 4 hard drives, and CD-ROM/floppy (like the Thinkpad 600
series where you choose which one of floppy or CD is external and which is
internal). This is all achievable with today's technology, and would cost
much less than $32000 if they made them.
As for Video. I am waiting for that, but expect I'll be waiting quite a
while.
--
Electronic information tampers with your soul.
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