Messages in this thread | | | Date | Wed, 18 Mar 1998 17:00:46 +0100 (W. Europe Standard Time) | From | Jan Gyselinck <> | Subject | Re: some memory/swap thoughts |
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On Wed, 18 Mar 1998, Andreas Kostyrka wrote: > On Wed, 18 Mar 1998, Jan Gyselinck wrote: > > Now, 5 meg as a cache, isn't that too much?? Some people think this is > Nope, I routinly run with 80MB swap (here and at home.) And it's a > difficult question, because there are tradeoffs: Either you want one bzip > to run fast, or you want a dozen bzip par. run with high troughput. I can't run a dozen bzip's with high troughput if I only have 16 meg RAM > (That's nicely demonstrated by EIDE/SCSI on a multiuser server: Replacing > a 5 yrs old SCSI disc with a new EIDE that was in benchmarks 3-4 times > faster resulted in grinding teh server to a halt. I had to replace EIDE > disc with a new SCSI disc, which again in benchmarks is about 50-60% of > the speed of the EIDE disc, but I can do background kernel recompiles > without anyone even noticing :) ). Yes, and my HD is slow, I know. > > needed, well I can tell you, it isn't. A year ago, I did some testing on > > a 486DX33 with 8 meg, running DOS/winslows 3.11. I tried different > > cache-sizes (with pc-cache) and measured the speedup while starting up > Comparing the Linux cache subsystem to SMARTDRV is like doing performance > testing on LADA and then applying the findings to BMW/Cadillac/... They > may hald true, but they may hold also not true! It wasn't smartdrive, it was pc-cache, that's somewhat better :p > > MS-Word. Maybe you think that's not the way to test this, but why not? > > You test the speed-up in real-life applications, because that's what you > > do all day. So, speedup from 0 to 64 kB cache, 20 seconds, from 64 to 128 > > kB cache, 14 seconds, from 128 to 256 kB, 6 seconds, from 256 to 512 kB, 3 > > seconds, and from 512 to 1024 kB, 1 second. Now why in gods name would > Again, on a Single-User box a different memory management may seem better. > (But what happens if the single-user becomes a power user and begins to > ``multitask'' heavily?) Maybe that's true. I only know that things were different (and maybe you can't notice that on that speed-monster of yours) > > one want 5 meg of cache? It will increase the speed of disk-activity with > > maybe 1 second of a 2,5 meg cache. My oppinion is that for 16 meg of > > memory, the minimum-limit for a disk-cache should be 256kB, not 5 meg!! > Nope, that sucks. I know how NeXT with 800kb-2MB cache runs on the same > hardware as Linux. Limiting the cache is not a very clever thing. I was talking about the minimum cache size, not the maximum. At the moment, on my machine, minimum cache size is 5 meg, and that's toooo much > > Okay, you say, but what about all those idling programs that are stuck in > > memory, and just take up memory from the cache. I know, I know, there are > > cases where it's needed to run such programs, but not always. People are > > running to many idle programs these days! Why do you think there is a > Nope. By definitation a process that does a sleep(3600); should not be a > hurden on the system. -> That's usual POSIX coding understanding. > And not all can be handled by inetd, and not all should be handled. > > inet-daemon? So that there don't need to be a dozen idle processes who > > are checking if there isn't something knocking on there port. Running 6 > They are not checking. They are blocked. And that means they are eligible > for swapping. > > or more agetty's? There exists something like a console spawn daemon, you > Nice. And what if each of the ``getty's'' does a different thing? (One > menu for system halt/restart/etc., one menu to restart gpm [Did you notice It was an example, every case and environment is different. > it's quite impossible to find GOOD 3 button trackballs today, especially > if you don't want to pay MEGABUCKs? I've got one here, that seems to > ``powerdown'' and needs to be restarted with button pressed, ...] I got one too, and it functions without problems. > > If I run a bash on a console, and I do something on another console for a > > while, and I return to the first one, I want the bash-process to respond > > immediatly to my key-strokes. I don't like to wait for it until it's > > loaded from swap. My opinion is this: if I run something, it is because > > it needs to run, and it must be able to respond immediatly. If this is > But Linux is Unix and by definition is a server OS. If you want a buggy > scheduler implementation, than go buy OS/2 or NT *g*. (I've seen a nice > SQL server for OS/2, but the scheduler was quite broken: It automatically > decreased the priority of the server if you minimized it. So the Server > had to run in foreground all the time, ...) So you actually _like_ having a slow OS?? I began with 1.2.13 on my portable, and that was _fast_. Previous linux kernels didn't do such aggressive memory-freeing. > > not so, I wont run it. I don't have memory to throw around, I need every > > bit. (And no, memory for a portable is not that cheap) > Than you want to use it more cleverly than to have say 900kb wasted on > bash blocked on read(0,..,..); 900kB? It's shared, maybe 500 kB is not shared. I want my system to swap if it's needed, not to have some more cache. Disks are quite fast now, and they cache a bit too. > > So think about this, when you people change something in the > >memory-management of linux, because it'll run on low-budget and > > high-budget systems... > The point is, that Linux is as a server OS more optimized for the > multitasking/multiuser troughput. And that's the complicated one: If you > want to run one thing a time, than DOS quite cut it :) ?? My point is: don't swap if it is not needed. Like I said, I do multi-task! > > > Jan Gyselink > > for the moment a swapping linux-user > Nothing bad about swapping. (And running bzip on a underpowered machine > was always painful. If it wouldn't be so painful, than bzip would have > long replaced gzip, right?) No? My machine doesn't respond when it swaps! And that's bad. I got not that much diskspace either, and bzip used to run fine. > > PS: i hope .90 is better, 'll try it tonight, but after I rebooted, > > because my console is messed up by Xwindows, who didn't restore the state > > after it finished (maybe caused by to much swapping?????) > Why should swapping influence this? *wonder* Euh, maybe because things got stalled??? > Andreas
Jan Gyselinck
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