Messages in this thread | | | From | "William J. Earl" <> | Date | Thu, 9 Dec 1999 15:42:10 -0800 (PST) | Subject | Re: Getting big areas of memory, in 2.3.x? |
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Alan Cox writes: > > That is not the case for loadable (modular) drivers. Loading st > > as a module, for example, after boot time sometimes works and sometimes does > > not, especially if you set the maximum buffer size larger (to, say, 128K, > > as is needed on some drives for good space efficiency). > > Dont mix up crap code with crap hardware. Scsi generic had similar problems > and has been fixed. There are very very few non scatter-gather scsi controllers
I only mentioned st as example of the inability to get a large page long after system startup. Large pages are good for a variety of purposes. For example, large pages for programs with large code or data footprints can dramatically reduce TLB misses. If the I/O system learns to do direct I/O, the overhead of setting up large I/O operations, whether for disk I/O or for OpenGL operations such as writing a large image to the screen (via DMA), is much reduced when the I/O is done from large pages. The CPU overhead of setting up I/O operations is pretty minimal when you are doing file I/O to and from a single IDE disk, but far from minimal for higher-bandwidth targets, such as a graphics controller or a HDTV camera.
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