49 lines
2.0 KiB
Plaintext
49 lines
2.0 KiB
Plaintext
.\"
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.\" ----------------------------------------------------------------------------
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.\" "THE BEER-WARE LICENSE" (Revision 42):
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.\" <phk@login.dknet.dk> wrote this file. As long as you retain this notice you
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.\" can do whatever you want with this stuff. If we meet some day, and you think
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.\" this stuff is worth it, you can buy me a beer in return. Poul-Henning Kamp
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.\" ----------------------------------------------------------------------------
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.\"
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.\" $FreeBSD$
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.\"
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.ds RH Conclusion and experience.
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.NH
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Conclusion and experience.
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.PP
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In general the performance differences between gnumalloc and this
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malloc are not that big.
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The major difference comes when primary storage is seriously
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over-committed, in which case gnumalloc
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wastes time paging in pages it's not going to use.
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In such cases as much as a factor of five in wall-clock time has
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been seen in difference.
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Apart from that gnumalloc and this implementation are pretty
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much head-on performance-wise.
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.PP
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Several legacy programs in the BSD 4.4 Lite distribution had
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code that depended on the memory returned from malloc
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being zeroed. In a couple of cases, free(3) was called more than
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once for the same allocation, and a few cases even called free(3)
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with pointers to objects in the data section or on the stack.
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.PP
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A couple of users have reported that using this malloc on other
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platforms yielded "pretty impressive results", but no hard benchmarks
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have been made.
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.ds RH Acknowledgements & references.
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.NH
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Acknowledgements & references.
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.PP
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The first implementation of this algorithm was actually a file system,
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done in assembler using 5-hole ``Baudot'' paper tape for a drum storage
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device attached to a 20 bit germanium transistor computer with 2000 words
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of memory, but that was many years ago.
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.PP
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Peter Wemm <peter@FreeBSD.org> came up with the idea to store the
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page-directory in mmap(2)'ed memory instead of in the heap.
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This has proven to be a good move.
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.PP
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Lars Fredriksen <fredriks@mcs.com> found and identified a
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fence-post bug in the code.
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