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Preload Drastically Boosts Linux Performance

Posted by kdawson on from the getting-in-line-early dept.

Nemilar writes "Preload is a Linux daemon that stores commonly-used libraries and binaries in memory to speed up access times, similar to the Windows Vista SuperFetch function. This article examines Preload and gives some insight into how much performance is gained for its total resource cost, and discusses basic installation and configuration to get you started."

9 of 144 comments (clear)

  1. LiveCDs do this... by SaidinUnleashed · · Score: 4, Informative

    This is exactly why live CDs like Damn Small Linux (and Knoppix, if you have a ton of ram) run so fast if you load the CD image to ram. Ram is fast!

    --
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    1. Re:LiveCDs do this... by Anonymous Coward · · Score: 4, Informative

      Make sure you pass the "toram" parameter when you boot the livecd at the kernel load prompt. You can press the various function keys at boot time to find the correct method.

    2. Re:LiveCDs do this... by Ibn+al-Hazardous · · Score: 5, Informative

      You start with a false presumption. I do not know what distro you use, and can't tell you if that does anything nifty - but "Linux" sure as hell does not do this already. If another app has already loaded as shared library, it may well be in RAM but it can just as well be swapped out. For all other cases, the answer is probably that your shared libraries are not cached or preloaded - and so this will give you quite a speed up.

      The thing that eats all your RAM is nothing Linux specific at all, it is your applications asking for more RAM than they are currently going to use. Why should they do such a thing? Well, what do you think memory management would look like if hundreds of apps, daemons and kernel threads ask for two bytes at a time? It'd paint a pretty fragmented picture, so they ask for gobs of pages at a time. Pages seldom touched get swapped out, but still there's an awesome amount of overallocation - thus your memory seems to be 100% allocated 100% of the time.

      So, preloading libs that are frequently used is probably going to use your RAM in a more meaningful way unless you already have a problem with constant swapping.

      --
      Yes, I am a biological organism. All rumors to the contrary are just that, rumors.
  2. Re:What, what? by guruevi · · Score: 5, Informative

    I don't know what rock you were under, but preload has been available for a while:

    preload 0.2 release: 2005-09-01

    And it was there before as it was packaged in Gentoo (back when it was still popular) and Suse 9.3

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  3. Nice but... by pizzach · · Score: 4, Informative

    I never had any luck with preload the times I tried it (a year or two ago?). Nowadays I use alltray for preloading often used apps that are a bit chunky such as Firefox or Openoffice. Openoffice also has a built in preload feature...but you can use alltray anyway for the same effect.

    --
    Once you start despising the jerks, you become one.
    1. Re:Nice but... by Nemilar · · Score: 4, Informative

      Alltray and preload are two totally different things. With Alltray, you're talking about keeping the application open, just minimized to the system tray. With Preload, you're talking about caching the binaries/libraries in memory so when you do open the application, it's reading the data from RAM rather than the hard drive. Sure, AllTray moves the load to RAM, but at the cost of entire applications. The point of preload is that it just caches the most commonly used files.

      --
      Nemilar http://www.techthrob.com - Visit Me!
  4. Re:But I thought Vista doing it = RAM hogging? by Anonymous Coward · · Score: 5, Informative

    Vista's implementation is marketed as being useful for older, slower machines with less RAM, where it actually may be unwanted, and could cause performance issues (unless it's disabled below a certain threshold - it might be). It's only really useful if you have lots of RAM (around 2GB or so). Yes, SuperFetch has an extra mode where it uses a USB-2 stick as a secondary disk cache, but that's not what we're talking about here. That mode is generally perceived as a gimmick.

    Linux handles having lots of RAM a lot better than Windows (XP) does, because of differences in the way the caching system was designed. Linux (and OS X) was intended to run entirely from RAM and use little swap. I've run, say, OpenOffice once, not used it for several weeks, and the next time I start it it loads almost instantly, because it was still sitting in the cache. My machines have 2GB of RAM, with much less than 500MB actually in use - the remaining 1.5GB is being used as disk cache. Swap usage is either zero, or very close. Of course, performance goes to hell if you do something that flushes the disk cache, or if you try using such a system on a machine with 256MB of RAM.

    Windows, on the other hand, was designed to run almost entirely from swap, and tends to drop stuff from the disk cache when it's not been used in a while, as well as moving stuff out to swap rather aggressively. That works great if you barely have enough RAM to run the OS, but it's terribly wasteful if you have more than enough RAM. In this case, SuperFetch is actually useful, allowing it to catch up to and actually surpass Linux, by monitoring which files are actually used and making sure they're already in the disk cache.

    That's great, although nothing new. Other OSes have had this for years (this Linux implementation dates back to 2005, Mac OS X has had it for ages, and neither implementation was original) - Microsoft were just the first to brand it.

    TFA said nothing about Vista's implementation.

    I think the primary problem people have with Microsoft's implementations is that they're typically very complicated, and have a tendency to degrade over time. XP is the typical whipping boy for this - none of the self-maintaining performance stuff (prefetching, or the prelinker) actually works for longer than about six months, meaning that an XP installation starts off fast, gradually gets faster, and then rapidly slows down as the system tries to speed itself up.

  5. Blogspam by bziman · · Score: 5, Informative

    The submitter is the author of the blog, and is merely paraphrasing the whitepaper written by the author of the software -- and that is two years old. Nothing new or interesting here, just someone trying to draw eyeballs to his blog.

  6. Re:What, what? by sqrammi · · Score: 5, Informative

    It's actually a little different than the preload that's been in Gentoo for years. The core functionality is of course the same, but now a daemon runs that caches libraries and updates the linkage periodically. So, it can possibly give much more performance, since everything is always up-to-date. It will be standard in Hardy Heron when it comes out.