On Tue, 2007-08-14 at 12:12 -0700, Christoph Lameter wrote: > On Tue, 14 Aug 2007, Andi Kleen wrote: > > > Christoph Lameter <[EMAIL PROTECTED]> writes: > > > > > Reclaim can be called with interrupts disabled in atomic reclaim. > > > vmscan.c is currently using spinlock_irq(). Switch to spin_lock_irqsave(). > > > > I like the idea in principle. If this fully works out we could > > potentially keep less memory free by default which would be a good > > thing in general: free memory is bad memory. > > Right. > > > But would be interesting to measure what the lock > > changes do to interrupt latency. Probably nothing good. > > Yup. > > > A more benign alternative might be to just set a per CPU flag during > > these critical sections and then only do atomic reclaim on a local > > interrupt when the flag is not set. That would make it a little less > > reliable, but much less intrusive and with some luck still give many > > of the benefits. > > There are other lock interactions that may cause problems. If we do not > switch to the saving of irq flags then all involved spinlocks must become > trylocks because the interrupt could have happened while the spinlock is > held. So interrupts must be disabled on locks acquired during an > interrupt.
A much simpler approach to this seems to use threaded interrupts like -rt does. - 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/
