> > > > Remove this function. It's purpose was to limit the global number of > > writeback pages from submitted by direct reclaim. But this is equally > > well accomplished by limited queue lengths. When this function was > > added, the device queues had much larger default lengths (8192 > > requests, now it's 128), causing problems. > > This changelog is wrong. > > Yes, the _default_ depth of CFQ was decreased. But it is trivial for the > user to inrcrease the queue depth again, and we'd prefer that the VM not > shit itself in response. > > Plus, more significantly, the queue is per-disk. A system with many disks > will easily be able to cover all memory with under-writeback pages. > Which is why the level of under-writeback memory is controlled at a higher > level. > > These variables are why we must not reply upon per-queue throttling in > VFS/MM/VM. > > > All that being said, the patch (with a new, correct changlog) is OK. This > is because we now control the amount of dirty memory in the machine by > running balance_dirty_pages() at first-write-fault time. So we can no > longer get into the situation where all memory is dirty+writeback.
Well, sort of. I think you are not taking SwapCache pages into account, which just pop up out of nothing to be turned into writeback pages. So I think removing this function still relies on limited queues, or some other method of limiting writeback. Miklos - 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/
