Messages in this thread | | | From | Mel Gorman <> | Subject | [PATCH 0/7] [RFC] Sizing zones and holes in an architecture independent manner V4 | Date | Mon, 24 Apr 2006 21:20:09 +0100 (IST) |
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This is V4 of the patchset to size zones and memory holes in an architecture-independent manner.
After this release, I would like to look at getting this into the -mm tree assuming there are no boot-related problems found before I would also like to hear some feedback. Andi has already stated for release V2 that he didn't think it helped x86_64 much, so later releases made more effort at reducing the x86_64-specific code. Andi, are you still concerned about the x86_64 changes? For the i386, ia64 and power maintainers, have you concerns or do you think these are ready to get some wider testing? For anyone else watching, code reviews and acks would be very welcome because my own testing cannot cover every machine configuration.
The reasons why I'd like to this merged include;
o Less architecture-specific code - particuarly for x86 and ppc64 o More maintainable. Changes to zone layout need only be made in one place o Zone-sizing and memory hole calculation is one less job that needs to be done for new architecture ports o With the architecture-independent representation, zone-based anti-fragmentation needs a lot less architecture-specific code making it more portable between architectures. This will be important for future hugepage-availability work o Nigel Cunningham has stated that that software suspend could potentially use the architecture-independent representation to discover what pages need to be saved during suspend
Changelog since V3 o Rebase to 2.6.17-rc2 o Allow the active regions to be cleared. Needed by x86_64 when it decides the SRAT table is bad half way through the registering of active regions o Fix for flatmem x86_64 machines booting
Changelog since V2 o Fix a bug where holes in lower zones get double counted o Catch the case where a new range is registered that is within an range o Catch the case where a zone boundary is within a hole o Use the EFI map for registering ranges on x86_64+numa o On IA64+NUMA, add the active ranges before rounding for granules o On x86_64, remove e820_hole_size and e820_bootmem_free and use arch-independent equivalents o On x86_64, remove the map walk in e820_end_of_ram() o Rename memory_present_with_active_regions, name ambiguous o Add absent_pages_in_range() for arches to call
Changelog since V1 o Correctly convert virtual and physical addresses to PFNs on ia64 o Correctly convert physical addresses to PFN on older ppc o When add_active_range() is called with overlapping pfn ranges, merge them o When a zone boundary occurs within a memory hole, account correctly o Minor whitespace damage cleanup o Debugging patch temporarily included
At a basic level, architectures define structures to record where active ranges of page frames are located. Once located, the code to calculate zone sizes and holes in each architecture is very similar. Some of this zone and hole sizing code is difficult to read for no good reason. This set of patches eliminates the similar-looking architecture-specific code.
The patches introduce a mechanism where architectures register where the active ranges of page frames are with add_active_range(). When all areas have been discovered, free_area_init_nodes() is called to initialise the pgdat and zones. The zone sizes and holes are then calculated in an architecture independent manner.
Patch 1 introduces the mechanism for registering and initialising PFN ranges Patch 2 changes ppc to use the mechanism - 128 arch-specific LOC removed Patch 3 changes x86 to use the mechanism - 150 arch-specific LOC removed Patch 4 changes x86_64 to use the mechanism - 96 arch-specific LOC removed Patch 5 changes ia64 to use the mechanism - 57 arch-specific LOC removed
At this point, there is a reduction of 431 architecture-specific lines of code and a net reduction of 52 lines. The arch-independent code is a lot easier to read in comparison to some of the arch-specific stuff, particularly in arch/i386/ .
For Patch 6, it was also noted that page_alloc.c has a *lot* of initialisation code which makes the file harder to read than it needs to be. Patch 6 creates a new file mem_init.c and moves a lot of initialisation code from page_alloc.c to it. After the patch is applied, there is still a net loss of 33 lines.
The patches have been successfully boot tested by me and verified that the zones are the correct size on
o x86, flatmem with 1.5GiB of RAM o x86, NUMAQ o PPC64, NUMA o PPC64, CONFIG_NUMA=n o Power, RS6000 with and without HIGHMEM enabled o x86_64, NUMA with SRAT o x86_64, NUMA with broken SRAT that falls back to k8topology discovery o x86_64, ACPI_NUMA, ACPI_MEMORY_HOTPLUG && !SPARSEMEM to trigger the hotadd path without sparsemem fun in srat.c (SRAT broken on test machine and I'm pretty sure the machine does not support physical memory hotadd anyway so test may not have been effective other than being a compile test.) o x86_64, CONFIG_NUMA=n o x86_64, AMD64 desktop machine with flatmem
Tony Luck has succesfully tested for ia64 on Itanium with tiger_defconfig, gensparse_defconfig and defconfig. Bob Picco has also tested and debugged on IA64. Jack Steiner successfully boot tested on a mammoth SGI IA64-based machine. These were on patches against 2.6.17-rc1 but there have been no ia64-changes made between release 3 and 4 of these patches.
There are differences in the zone sizes for x86_64 as the arch-specific code for x86_64 accounts the kernel image and the starting mem_maps as memory holes but the architecture-specific code accounts the memory as present.
The net reduction seems small but the big benefit of this set of patches is the reduction of 431 lines of architecture-specific code, some of which is very hairy. There should be a greater net reduction when other architectures use the same mechanisms for zone and hole sizing but I lack the hardware to test on.
Comments?
Additional credit; Dave Hansen for the initial suggestion and comments on early patches Andy Whitcroft for reviewing early versions and catching numerous errors Tony Luck for testing and debugging on IA64 Bob Picco for testing and fixing bugs related to pfn registration Jack Steiner and Yasunori for testing on IA64
arch/i386/Kconfig | 8 arch/i386/kernel/setup.c | 19 arch/i386/kernel/srat.c | 98 ---- arch/i386/mm/discontig.c | 59 -- arch/ia64/Kconfig | 3 arch/ia64/mm/contig.c | 60 -- arch/ia64/mm/discontig.c | 41 - arch/ia64/mm/init.c | 12 arch/powerpc/Kconfig | 13 arch/powerpc/mm/mem.c | 53 -- arch/powerpc/mm/numa.c | 157 ------ arch/ppc/Kconfig | 3 arch/ppc/mm/init.c | 26 - arch/x86_64/Kconfig | 3 arch/x86_64/kernel/e820.c | 109 +--- arch/x86_64/kernel/setup.c | 6 arch/x86_64/mm/init.c | 62 -- arch/x86_64/mm/k8topology.c | 3 arch/x86_64/mm/numa.c | 18 arch/x86_64/mm/srat.c | 10 include/asm-ia64/meminit.h | 1 include/asm-x86_64/e820.h | 5 include/asm-x86_64/proto.h | 2 include/linux/mm.h | 19 include/linux/mmzone.h | 15 mm/Makefile | 2 mm/mem_init.c | 1044 ++++++++++++++++++++++++++++++++++++++++++ mm/page_alloc.c | 678 ---------------------------- 28 files changed, 1248 insertions(+), 1281 deletions(-) -- -- Mel Gorman Part-time Phd Student Linux Technology Center University of Limerick IBM Dublin Software Lab - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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