[PATCH] hashed waitqueues, somewhat cleaner

From: William Lee Irwin III (wli@holomorphy.com)
Date: Sun Jan 06 2002 - 21:34:17 EST

Some new versions of the hashed waitqueues are now available:


This includes:

(1) Manual common subexpression elimination of page_waitqueue() calls
(2) Use a 64-bit Fibonacci hashing prime conditional on BITS_PER_LONG
(3) Storing wait_table_shift instead of wait_table_bits to reduce
        arithmetic within the hash function
(4) Eliminating the masking operation within the hash function, as
        the shifting already zeroes the high-order bits.
(5) Eliminating explicit references to struct page ->wait outside
        of the VM.

Future directions:
(1) Using a non-linear function to size the waitqueue table given the
        size of a zone, as the demand for waitqueues does not appear to
        scale linearly with the size of memory.
(2) Finding bit-sparse Fibonacci hashing multipliers for machines with
        slow integer multiplies (so it can be optimized to shift/add
        sequences on those machines).

I'll followup shortly after rediffing against 2.4.17-mainline.

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