On computers with CPU speeds less than ~800 MHz, all Linux distros I've tried exhibit cursor lag under CPU load. The cursor freezes in place for several seconds, and mouse clicks have no effect. The system thus gets very unresponsive when rendering a web page, installing a package, etc.

- Decreasing swappiness, reducing dirty_bytes, and other sysctl vm tweaks do not help
- Disabling nohz/highres does not help
- Using a specific X driver (as opposed to fbdev, which works better on old machines) does not help
- Enabling ShadowFB (or disabling it, as applicable) does nothing
- Using 16-bit color does not help
- Lowering Xorg's niceness does not help

On Windows 2000 this problem does not exist, period. 400 MHz computers maintain full GUI responsiveness except under extremely high load, and the cursor never lags the slightest bit, even when hardware acceleration is entirely disabled. On Win2k, Opera can render Facebook just fine and dandy; on Linux it comes close to freezing X.

Is there any way I can kill this lag, or am I SOL with current kernels? As it is, my legacy machines are unusable with modern Linux distros; it often takes several seconds for a mouse click to register when doing routine stuff.

(The machines are a Mac G3 (blue and white) and a Thinkpad 600E. I've tried Debian on the Mac, and Salix, Debian, and Tiny Core on the Thinkpad. I want Linux on the Thinkpad for security reasons, and on the Mac because it's the only modern OS that's supported halfway decently.)

Do these computer use Nvidia graphics? If so, install the driver from Nvidia.

Unfortunately no, and if they did the cards would be too old. The Mac has a Rage 128 and the Thinkpad has some NeoMagic card. The r128 driver cannot achieve more than 800x600 resolution on the Mac, and the neomagic driver is as slow on the Thinkpad as the vesa driver (and present on fewer distros).

BTW I don't expect good performance from these computers, in terms of web page rendering speeds, application launch times, etc. But I expect the GUIs to be usable during day to day stuff, because that is the case under Windows 2000 and XP. On Linux it is not.

http://en.wikipedia.org/wiki/Moore%27s_law

Windows 2000 is not an applicable comparison to 2012 linux distros with 3.x kernels. 12 years = 2 to the 5th = Windows 2k was designed for computers with 1/32nd the resources on average compared with operating systems of 2012.

You could try DSL (2.4 kernel) or any recent distro with 2.6 kernel.

But why not upgrade your hardware? How many seconds of your precious time watching the cursor crawl across the screen of a mac G3 (street value maybe $20)?

That's not a new symptom. Woodsman made a series of posts in his blog about looking for a distro for old hardware and he came to the same conclusion: that none of the environments available for the mom and pop users could out-perform his Windows NT 4.0.
Out of curiosity, have you tried using wms like WindowMaker and Fluxbox and use Midori as a web-browser? I ask that because I have a Presario 700 US and trying to run XFCE is painful, but Fluxbox does reasonably ok. If you want something really light-weight, go with OpenBSD. It's waaaaay lighter than Linux - I could run KDE 3.5.10 there, albeit a little slowly.

Tried Fluxbox and a webkit-based browser. Cursor still lags a lot.

Haven't tried OpenBSD on the Mac, because it requires some hacks to make it bootable. (You have to boot with an OS 9 CD and stuff.) But I may try it on the Thinkpad. Got nothing to lose there in terms of power management, since it doesn't support ACPI.

snowpine: Linux (Maemo) works fine on cell phones not much more powerful than the G3, albeit at lower screen resolution. Linux has been used on much less powerful embedded systems, even with X11. Being a modern OS does not (and should not) imply that it will not work on older computers.

I got some lag of this type before. I suspect it is caused by either I/O hogging of some write process and/or by bad CPU scheduling.

All issues were fixed by compiling a 3.2 kernel and I also am using zcache. The issue has disappeared since this, so it may be worth a try. Technically, compared to previous kernels I also enabled hugepage support and cleancache.

I was probably wrong then. However, I meant midori and not webkit-based browser. Chrome and Chromium are resource-hogs.

You're wrong about that last part, actually. All software has minimum hardware requirements, below which it may not run satisfactorily. Here are the published recommendations for Debian; does your Mac G3 meet them?

It sounds like you have "ignored these suggestions" and are therefore "frustrated," just as the Debian documentation warned. Your iMac G3 was a low end computer in 1998; as you yourself point out, the average 2012 smartphone is more powerful, a phenomenon called "Moore's Law."

I have a Thinkpad underclocked to 600MHz, on which I use Salix. It's not exactly fast, but I haven't noticed cursor lag.

I suspect the difference between your Opera Win2k install and your Opera Linux install is that the Win2k install has the latest browser.js and the Linux one does not.

http://www.opera.com/docs/browserjs/
http://my.opera.com/sitepatching/blo...yping-problems

What video card? I'm beginning to suspect these problems are all X11.

It's not just Opera though. On Linux, the cursor freezes when opening application menus, for instance.

As for Linux on my Thinkpad... It's unfortunate but I guess I'll be sticking with Win2k. It's not as secure as I'd like, but it does everything I need. Shame it doesn't run on Macs.

Re upgrading the hardware: because of the widespread use of Congoese tantalum, the use of effective slave labor in the manufacture of computers, and the unhealthy conditions in computer recycling plants, I try to avoid buying new hardware if possible. Instead I prefer to get the most out of the "obsolete" computers I have. Perhaps it's a bit presumptuous of me to expect a modern OS to work as well as Win2k on the older ones... I'd just like something with better multiuser support than Win2k (let alone MacOS 9, which is purely single user). Sorry if I come off as kind of snobby.

Then you have either tried the wrong distros or your workload is just to much for that machines, I would assume.
I run a trimmed down Slackware 13.37 with a kernel specifically compiled for that machine with wmii as window manager on my Asus eeePC 4G (630 MHz Celeron Mobile, 512MB RAM) and have absolutely no cursor lags or something similar.

And this has a simple reason: They run a customized kernel and customized software (most likely it will not be Xorg's xserver that you see there, but TinyX, XVesa or some custom stuff, for example), all chosen to fit to the specs for those machines and all compiled to get the most out of it. They don't run all-purpose desktop distros that have been compiled to run on anything from i486 upwards, That would be to excessive on CPU power and size.
If you want something really fast then try it with LFS or one of the source based distros, this way you will get the best speed. Tip: Do the compiling stuff in a VM on a powerful system and copy the results over to the low-spec machines, will save some time.

An update...

I managed to get FreeBSD 9 installed on the Thinkpad. It boots pretty slowly, but once it's up and running it's fast enough. Not Win2k fast, and certainly not as user-friendly as Win2k, but more than on par in terms of features. And input does not lag at all. Not when installing packages, not when rendering web pages, etc. Some applications are kind of slow (yay GTK2), but in general it is quite usable.

My setup, FWIW:
- XDM as the login manager
- wmii 3.6 as my window manager
- xxxterm as my browser
- clex and uxterm to manage my files
- the automounter daemon manages anything mountable

Total memory use as I type this is 81 MB... Actually it was 64MB a few minutes ago, maybe there's a memory leak in xxxterm. :P Anyway this is probably 30-50% less memory usage than a similar Linux setup, or thereabouts.

Three cheers for BSD! :P