forked from luck/tmp_suning_uos_patched
4c21e2f244
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> |
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| drivers | ||
| include | ||
| kernel | ||
| os-Linux | ||
| scripts | ||
| sys-i386 | ||
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| sys-ppc | ||
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| config.release | ||
| defconfig | ||
| Kconfig | ||
| Kconfig.char | ||
| Kconfig.debug | ||
| Kconfig.i386 | ||
| Kconfig.net | ||
| Kconfig.scsi | ||
| Kconfig.x86_64 | ||
| Makefile | ||
| Makefile-i386 | ||
| Makefile-ia64 | ||
| Makefile-os-Linux | ||
| Makefile-ppc | ||
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| Makefile-x86_64 | ||