mirror of
https://github.com/torvalds/linux.git
synced 2026-07-27 09:36:22 +02:00
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> |
||
|---|---|---|
| .. | ||
| boot | ||
| common | ||
| configs | ||
| kernel | ||
| lib | ||
| mach-aaec2000 | ||
| mach-clps711x | ||
| mach-clps7500 | ||
| mach-ebsa110 | ||
| mach-epxa10db | ||
| mach-footbridge | ||
| mach-h720x | ||
| mach-imx | ||
| mach-integrator | ||
| mach-iop3xx | ||
| mach-ixp4xx | ||
| mach-ixp2000 | ||
| mach-l7200 | ||
| mach-lh7a40x | ||
| mach-omap1 | ||
| mach-pxa | ||
| mach-rpc | ||
| mach-s3c2410 | ||
| mach-sa1100 | ||
| mach-shark | ||
| mach-versatile | ||
| mm | ||
| nwfpe | ||
| oprofile | ||
| plat-omap | ||
| tools | ||
| vfp | ||
| Kconfig | ||
| Kconfig.debug | ||
| Makefile | ||