On Tue, Jul 17, 2007 at 10:47:37AM -0700, William Lee Irwin III wrote: >> You may rest assured that it's technically feasible. It's been done. >> The larger obstacles to all this are nontechnical.
On Tue, Jul 17, 2007 at 09:33:08PM +0200, Andrea Arcangeli wrote: > Back then there was no variable order page size proposal, no slub, > generally nothing of that kind. > I think these days it worth to get it working again and solve the > technical obstacles once more time. Then we should plug into it a > pagecache logic to handle small files. That means if the soft page > size is 64k, we should kmalloc 32k of pagecache if the file is < 64k > but >= 32k, or kmalloc 16k if the file is < 32k but >= 16k, etc... Actually I'd worked on what was called MPSS (Multiple Page Size Support) before I ever started on pgcl. Some large portion of the pgcl proposal as I presented it internally was to reduce the order of large page allocations and provide a promotion and demotion mechanism enabling different processes to have different sized translations for the same large page, and hence no out-of-context pagetable/TLB updates during promotion and demotion, essentially by making the TLB translation to page relation M:N. ISTR describing this in a KS presentation for which IIRC you were present. But that's neither here nor there. On Tue, Jul 17, 2007 at 09:33:08PM +0200, Andrea Arcangeli wrote: > Down to 32bytes if we memcpy the 32bytes away to a 64k page, and we > disable the logic the moment somebody attempts to mmap the "kmalloced" > pagecache (which I think it's a lot simpler than trying to mmap a > kmalloced 4k naturally aligned object into userland). I wouldn't call > it tail packing, it's more a fine-granular pagecache with the already > available kmalloc granularities. That will maximize pagecache > utilization with read syscall for hg/git compared to current 2.6.22 > plus memory will be allocated faster in 64k chunks etc... Ideally it > should be possible to disable the finer-granular-kmalloc-pagecache on > the big irons with lots of memory and only working with big files. In any event, that is a sound strategy for mitigating internal fragmentation of pagecache, though internal fragmentation of anonymous memory has more severe consequences and is less easily mitigated. -- wli - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
