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    SubjectRe: Couldn't get a free page
    On Mon, 10 Mar 1997, Leonard N. Zubkoff wrote:

    > Date: Mon, 10 Mar 1997 09:18:47 -0500 (EST)
    > From: "Richard B. Johnson" <>
    > Hello memory manager wizards........
    > What #define do I change and were to get some more pages for Disc I/O?
    > I can't write a large amount of data to a raw SCSI device for testing.
    > I use the BusLogic driver. It gets memory for "DMA" from the kernel.
    > It runs out and hangs.
    > The BusLogic driver itself should never hang waiting for DMA memory. The only
    > place it asks for memory after initialization is if it decides to expand the
    > number of CCBs. In that case, it calls with GFP_ATOMIC and should handle not
    > being able to create any.
    > I would think the DMA memory allocations are coming from the SCSI disk driver
    > itself (sd.c). I think there are some magic files in /proc that can reserve
    > more free pages, but I've never tried them.
    > Leonard

    Okay. I'll check some more. I am trying to isolate a possible file-system
    problem that occurs with _VERY_LARGE_ files. To isolate specific file-systems
    I am trying to write to a raw SCSI device just to make sure I can read
    what I write, i.e., is it a driver problem instead of a file-system problem.
    So far, I can't write directly to the raw device without a "free-page" hang.

    This may not be a problem in the "real" world because the kernel will get
    a chance to free up FS buffers to make more free pages. However, when I
    don't have the file-system cache, the SCSI interface has got to have
    enough buffers to fill it's cached-write SCB queue.

    Dick Johnson
    Richard B. Johnson
    Project Engineer
    Analogic Corporation
    Voice : (508) 977-3000 ext. 3754
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