On Thu, Jul 23, 2015 at 05:32:03PM -0600, Toshi Kani wrote: > On Thu, 2015-07-23 at 14:54 -0700, Spencer Baugh wrote: > > From: Joern Engel <joern@xxxxxxxxx> > > > > Mapping large memory spaces can be slow and prevent high-priority > > realtime threads from preempting lower-priority threads for a long time. > > Yes, and one of the goals of large page ioremap support is to address such > problem. Nice! Once we upgrade we should retest this one then. > > ------------[ cut here ]------------ > > WARNING: at arch/x86/kernel/irq.c:182 do_IRQ+0x126/0x140() > > Thread not rescheduled for 95 jiffies > > CPU: 14 PID: 6684 Comm: foo Tainted: G W O 3.10.59+ > > 0000000000000009 ffff883f7fbc3ee0 ffffffff8163a12c ffff883f7fbc3f18 > > ffffffff8103f131 ffff887f48275ac0 000000000000002f 000000000000007c > > 0000000000000000 00007fadd1e00000 ffff883f7fbc3f78 ffffffff8103f19c > > Call Trace: > > <IRQ> [<ffffffff8163a12c>] dump_stack+0x19/0x1b > > [<ffffffff8103f131>] warn_slowpath_common+0x61/0x80 > > [<ffffffff8103f19c>] warn_slowpath_fmt+0x4c/0x50 > > [<ffffffff810bd917>] ? rcu_irq_exit+0x77/0xc0 > > [<ffffffff8164a556>] do_IRQ+0x126/0x140 > > [<ffffffff816407ef>] common_interrupt+0x6f/0x6f > > <EOI> [<ffffffff81640483>] ? _raw_spin_lock+0x13/0x30 > > [<ffffffff8111b621>] __pte_alloc+0x31/0xc0 > > [<ffffffff8111feac>] remap_pfn_range+0x45c/0x470 > > remap_pfn_range() does not have large page mappings support yet. So, yes, > this can still take a long time at this point. We can extend large page > support for this interface if necessary. A cond_resched() is enough to solve the latency impact. But I suspect large pages will perform better as well, so having that support would be appreciated. > > [<ffffffffa007f1f8>] vfio_pci_mmap+0x148/0x210 [vfio_pci] > > [<ffffffffa0025173>] vfio_device_fops_mmap+0x23/0x30 [vfio] > > [<ffffffff81124ed8>] mmap_region+0x3d8/0x5e0 > > [<ffffffff811253e5>] do_mmap_pgoff+0x305/0x3c0 > > [<ffffffff8126f3f3>] ? call_rwsem_down_write_failed+0x13/0x20 > > [<ffffffff81111677>] vm_mmap_pgoff+0x67/0xa0 > > [<ffffffff811237e2>] SyS_mmap_pgoff+0x272/0x2e0 > > [<ffffffff810067e2>] SyS_mmap+0x22/0x30 > > [<ffffffff81648c59>] system_call_fastpath+0x16/0x1b > > ---[ end trace 6b0a8d2341444bde ]--- Jörn -- A defeated army first battles and then seeks victory. -- Sun Tzu -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>