diff options
Diffstat (limited to 'share/doc/papers/malloc/conclusion.ms')
| -rw-r--r-- | share/doc/papers/malloc/conclusion.ms | 48 |
1 files changed, 48 insertions, 0 deletions
diff --git a/share/doc/papers/malloc/conclusion.ms b/share/doc/papers/malloc/conclusion.ms new file mode 100644 index 000000000000..da7d7e98bdb5 --- /dev/null +++ b/share/doc/papers/malloc/conclusion.ms @@ -0,0 +1,48 @@ +.\" +.\" ---------------------------------------------------------------------------- +.\" "THE BEER-WARE LICENSE" (Revision 42): +.\" <phk@FreeBSD.org> wrote this file. As long as you retain this notice you +.\" can do whatever you want with this stuff. If we meet some day, and you think +.\" this stuff is worth it, you can buy me a beer in return. Poul-Henning Kamp +.\" ---------------------------------------------------------------------------- +.\" +.\" $FreeBSD$ +.\" +.ds RH Conclusion and experience. +.NH +Conclusion and experience. +.PP +In general the performance differences between gnumalloc and this +malloc are not that big. +The major difference comes when primary storage is seriously +over-committed, in which case gnumalloc +wastes time paging in pages it's not going to use. +In such cases as much as a factor of five in wall-clock time has +been seen in difference. +Apart from that gnumalloc and this implementation are pretty +much head-on performance-wise. +.PP +Several legacy programs in the BSD 4.4 Lite distribution had +code that depended on the memory returned from malloc +being zeroed. In a couple of cases, free(3) was called more than +once for the same allocation, and a few cases even called free(3) +with pointers to objects in the data section or on the stack. +.PP +A couple of users have reported that using this malloc on other +platforms yielded "pretty impressive results", but no hard benchmarks +have been made. +.ds RH Acknowledgements & references. +.NH +Acknowledgements & references. +.PP +The first implementation of this algorithm was actually a file system, +done in assembler using 5-hole ``Baudot'' paper tape for a drum storage +device attached to a 20 bit germanium transistor computer with 2000 words +of memory, but that was many years ago. +.PP +Peter Wemm <peter@FreeBSD.org> came up with the idea to store the +page-directory in mmap(2)'ed memory instead of in the heap. +This has proven to be a good move. +.PP +Lars Fredriksen <fredriks@mcs.com> found and identified a +fence-post bug in the code. |