Re: mmap() is slower than read() on SCSI/IDE on 2.0 and 2.1

Jay Nordwick (nordwick@scam.XCF.Berkeley.EDU)
Mon, 14 Dec 1998 20:54:23 -0800

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>I'd say that most apps use a fixed "buffer size". "cat" or "dd" use
>0.5 to 8k buffers. That's constant buffer.
>

With read() you can know that requests are coming in PAGE_SIZE*n, n>1,
so you can prefetch more than a singe page. With mmap() that
information is lost, you only see read os PAGE_SIZE.

> Roger.
>

-jay

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