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2005-11-23[PATCH] mm: update split ptlock KconfigHugh Dickins
Closer attention to the arithmetic shows that neither ppc64 nor sparc really uses one page for multiple page tables: how on earth could they, while pte_alloc_one returns just a struct page pointer, with no offset? Well, arm26 manages it by returning a pte_t pointer cast to a struct page pointer, harumph, then compensating in its pmd_populate. But arm26 is never SMP, so it's not a problem for split ptlock either. And the PA-RISC situation has been recently improved: CONFIG_PA20 works without the 16-byte alignment which inflated its spinlock_t. But the current union of spinlock_t with private does make the 7xxx struct page significantly larger, even without debug, so disable its split ptlock. Signed-off-by: Hugh Dickins <hugh@veritas.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-11-07[PATCH] Suppress split ptlock on arches which may use one page for multiple ↵Hugh Dickins
page tables Suppress split ptlock on arches which may use one page for multiple page tables. Reconsider what better to do (particularly on ppc64) later on. Signed-off-by: Hugh Dickins <hugh@veritas.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-10-29[PATCH] memory hotplug: sysfs and add/remove functionsDave Hansen
This adds generic memory add/remove and supporting functions for memory hotplug into a new file as well as a memory hotplug kernel config option. Individual architecture patches will follow. For now, disable memory hotplug when swsusp is enabled. There's a lot of churn there right now. We'll fix it up properly once it calms down. Signed-off-by: Matt Tolentino <matthew.e.tolentino@intel.com> Signed-off-by: Dave Hansen <haveblue@us.ibm.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-10-29[PATCH] mm: split page table lockHugh Dickins
Christoph Lameter demonstrated very poor scalability on the SGI 512-way, with a many-threaded application which concurrently initializes different parts of a large anonymous area. This patch corrects that, by using a separate spinlock per page table page, to guard the page table entries in that page, instead of using the mm's single page_table_lock. (But even then, page_table_lock is still used to guard page table allocation, and anon_vma allocation.) In this implementation, the spinlock is tucked inside the struct page of the page table page: with a BUILD_BUG_ON in case it overflows - which it would in the case of 32-bit PA-RISC with spinlock debugging enabled. Splitting the lock is not quite for free: another cacheline access. Ideally, I suppose we would use split ptlock only for multi-threaded processes on multi-cpu machines; but deciding that dynamically would have its own costs. So for now enable it by config, at some number of cpus - since the Kconfig language doesn't support inequalities, let preprocessor compare that with NR_CPUS. But I don't think it's worth being user-configurable: for good testing of both split and unsplit configs, split now at 4 cpus, and perhaps change that to 8 later. There is a benefit even for singly threaded processes: kswapd can be attacking one part of the mm while another part is busy faulting. Signed-off-by: Hugh Dickins <hugh@veritas.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-09-17[PATCH] fix mm/Kconfig spellingDave Hansen
Signed-off-by: Dave Hansen <haveblue@us.ibm.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-09-05[PATCH] sparsemem extreme implementationBob Picco
With cleanups from Dave Hansen <haveblue@us.ibm.com> SPARSEMEM_EXTREME makes mem_section a one dimensional array of pointers to mem_sections. This two level layout scheme is able to achieve smaller memory requirements for SPARSEMEM with the tradeoff of an additional shift and load when fetching the memory section. The current SPARSEMEM implementation is a one dimensional array of mem_sections which is the default SPARSEMEM configuration. The patch attempts isolates the implementation details of the physical layout of the sparsemem section array. SPARSEMEM_EXTREME requires bootmem to be functioning at the time of memory_present() calls. This is not always feasible, so architectures which do not need it may allocate everything statically by using SPARSEMEM_STATIC. Signed-off-by: Andy Whitcroft <apw@shadowen.org> Signed-off-by: Bob Picco <bob.picco@hp.com> Signed-off-by: Dave Hansen <haveblue@us.ibm.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-09-05[PATCH] SPARSEMEM EXTREMEBob Picco
A new option for SPARSEMEM is ARCH_SPARSEMEM_EXTREME. Architecture platforms with a very sparse physical address space would likely want to select this option. For those architecture platforms that don't select the option, the code generated is equivalent to SPARSEMEM currently in -mm. I'll be posting a patch on ia64 ml which uses this new SPARSEMEM feature. ARCH_SPARSEMEM_EXTREME makes mem_section a one dimensional array of pointers to mem_sections. This two level layout scheme is able to achieve smaller memory requirements for SPARSEMEM with the tradeoff of an additional shift and load when fetching the memory section. The current SPARSEMEM -mm implementation is a one dimensional array of mem_sections which is the default SPARSEMEM configuration. The patch attempts isolates the implementation details of the physical layout of the sparsemem section array. ARCH_SPARSEMEM_EXTREME depends on 64BIT and is by default boolean false. I've boot tested under aim load ia64 configured for ARCH_SPARSEMEM_EXTREME. I've also boot tested a 4 way Opteron machine with !ARCH_SPARSEMEM_EXTREME and tested with aim. Signed-off-by: Andy Whitcroft <apw@shadowen.org> Signed-off-by: Bob Picco <bob.picco@hp.com> Signed-off-by: Dave Hansen <haveblue@us.ibm.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-06-23[PATCH] sparsemem memory modelAndy Whitcroft
Sparsemem abstracts the use of discontiguous mem_maps[]. This kind of mem_map[] is needed by discontiguous memory machines (like in the old CONFIG_DISCONTIGMEM case) as well as memory hotplug systems. Sparsemem replaces DISCONTIGMEM when enabled, and it is hoped that it can eventually become a complete replacement. A significant advantage over DISCONTIGMEM is that it's completely separated from CONFIG_NUMA. When producing this patch, it became apparent in that NUMA and DISCONTIG are often confused. Another advantage is that sparse doesn't require each NUMA node's ranges to be contiguous. It can handle overlapping ranges between nodes with no problems, where DISCONTIGMEM currently throws away that memory. Sparsemem uses an array to provide different pfn_to_page() translations for each SECTION_SIZE area of physical memory. This is what allows the mem_map[] to be chopped up. In order to do quick pfn_to_page() operations, the section number of the page is encoded in page->flags. Part of the sparsemem infrastructure enables sharing of these bits more dynamically (at compile-time) between the page_zone() and sparsemem operations. However, on 32-bit architectures, the number of bits is quite limited, and may require growing the size of the page->flags type in certain conditions. Several things might force this to occur: a decrease in the SECTION_SIZE (if you want to hotplug smaller areas of memory), an increase in the physical address space, or an increase in the number of used page->flags. One thing to note is that, once sparsemem is present, the NUMA node information no longer needs to be stored in the page->flags. It might provide speed increases on certain platforms and will be stored there if there is room. But, if out of room, an alternate (theoretically slower) mechanism is used. This patch introduces CONFIG_FLATMEM. It is used in almost all cases where there used to be an #ifndef DISCONTIG, because SPARSEMEM and DISCONTIGMEM often have to compile out the same areas of code. Signed-off-by: Andy Whitcroft <apw@shadowen.org> Signed-off-by: Dave Hansen <haveblue@us.ibm.com> Signed-off-by: Martin Bligh <mbligh@aracnet.com> Signed-off-by: Adrian Bunk <bunk@stusta.de> Signed-off-by: Yasunori Goto <y-goto@jp.fujitsu.com> Signed-off-by: Bob Picco <bob.picco@hp.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-06-23[PATCH] generify memory presentAndy Whitcroft
Allow architectures to indicate that they will be providing hooks to indice installed memory areas, memory_present(). Provide prototypes for the i386 implementation. Signed-off-by: Andy Whitcroft <apw@shadowen.org> Signed-off-by: Dave Hansen <haveblue@us.ibm.com> Signed-off-by: Martin Bligh <mbligh@aracnet.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-06-23[PATCH] mm/Kconfig: give DISCONTIG more help textDave Hansen
This gives DISCONTIGMEM a bit more help text to explain what it does, not just when to choose it. Signed-off-by: Dave Hansen <haveblue@us.ibm.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-06-23[PATCH] mm/Kconfig: hide "Memory Model" selection menuDave Hansen
I got some feedback from users who think that the new "Memory Model" menu is a little invasive. This patch will hide that menu, except when CONFIG_EXPERIMENTAL is enabled *or* when an individual architecture wants it. An individual arch may want to enable it because they've removed their arch-specific DISCONTIG prompt in favor of the mm/Kconfig one. Signed-off-by: Dave Hansen <haveblue@us.ibm.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-06-23[PATCH] sparsemem: fix minor "defaults" issue in mm/KconfigDave Hansen
The following patch applies on top of 2.6.12-rc2-mm1. It fixes a minor user interaction issue, and an early reference to SPARSEMEM. This "choice" menu would always default to FLATMEM, as it was listed first. Move it to the end so that the other defaults have a chance first. Signed-off-by: Dave Hansen <haveblue@us.ibm.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-06-23[PATCH] Introduce new Kconfig option for NUMA or DISCONTIGDave Hansen
There is some confusion that arose when working on SPARSEMEM patch between what is needed for DISCONTIG vs. NUMA. Multiple pg_data_t's are needed for DISCONTIGMEM or NUMA, independently. All of the current NUMA implementations require an implementation of DISCONTIG. Because of this, quite a lot of code which is really needed for NUMA is actually under DISCONTIG #ifdefs. For SPARSEMEM, we changed some of these #ifdefs to CONFIG_NUMA, but that broke the DISCONTIG=y and NUMA=n case. Introducing this new NEED_MULTIPLE_NODES config option allows code that is needed for both NUMA or DISCONTIG to be separated out from code that is specific to DISCONTIG. One great advantage of this approach is that it doesn't require every architecture to be converted over. All of the current implementations should "just work", only the ones implementing SPARSEMEM will have to be fixed up. The change to free_area_init() makes it work inside, or out of the new config option. Signed-off-by: Dave Hansen <haveblue@us.ibm.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-06-23[PATCH] create mm/Kconfig for arch-independent memory optionsDave Hansen
With sparsemem being introduced, we need a central place for new memory-related .config options: mm/Kconfig. This allows us to remove many of the duplicated arch-specific options. The new option, CONFIG_FLATMEM, is there to enable us to detangle NUMA and DISCONTIGMEM. This is a requirement for sparsemem because sparsemem uses the NUMA code without the presence of DISCONTIGMEM. The sparsemem patches use CONFIG_FLATMEM in generic code, so this patch is a requirement before applying them. Almost all places that used to do '#ifndef CONFIG_DISCONTIGMEM' should use '#ifdef CONFIG_FLATMEM' instead. Signed-off-by: Andy Whitcroft <apw@shadowen.org> Signed-off-by: Dave Hansen <haveblue@us.ibm.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>