On Tue, Mar 09, 2010 at 06:42:02PM -0600, Kevin Day wrote: > > On Mar 9, 2010, at 4:27 PM, John Baldwin wrote: > > > On Tuesday 09 March 2010 3:40:26 pm Kevin Day wrote: > >> > >> > >> If I boot up on an Opteron 2218 system, it boots normally. If I boot the > > exact same VM moved to a 2352, I get: > >> > >> acpi0: <INTEL 440BX> on motherboard > >> PCIe: Memory Mapped configuration base @ 0xe0000000 > >> (very long pause) > >> ioapic0: routing intpin 9 (ISA IRQ 9) to lapic 0 vector 48 > >> acpi0: [MPSAFE] > >> acpi0: [ITHREAD] > >> > >> then booting normally. > > > > It's probably worth adding some printfs to narrow down where the pause is > > happening. This looks to be all during the acpi_attach() routine, so maybe > > you can start there. > > Okay, good pointer. This is what I've narrowed down: > > acpi_enable_pcie() calls pcie_cfgregopen(). It's called here with > pcie_cfgregopen(0xe0000000, 0, 255). inside pcie_cfgregopen, the pause starts > here: > > /* XXX: We should make sure this really fits into the direct map. */ > pcie_base = (vm_offset_t)pmap_mapdev(base, (maxbus + 1) << 20); > > pmap_mapdev calls pmap_mapdev_attr, and in there this evaluates to true: > > /* > * If the specified range of physical addresses fits within the direct > * map window, use the direct map. > */ > if (pa < dmaplimit && pa + size < dmaplimit) { > > so we call pmap_change_attr which called pmap_change_attr_locked. It's > changing 0x10000000 bytes starting at 0xffffff00e0000000. The very last line > before returning from pmap_change_attr_locked is: > > pmap_invalidate_cache_range(base, tmpva); > > And this is where the delay is. This is calling MFENCE/CLFLUSH in a loop 8 > million times. We actually had a problem with CLFLUSH causing panics on these > same CPUs under Xen, which is partially why we're looking at VMware now. (see > kern/138863). I'm wondering if VMware didn't encounter the same problem and > replace CLFLUSH with a software emulated version that is far slower... based > on the speed is probably invalidating the entire cache. A quick change to > pmap_invalidate_cache_range to just clear the entire cache if the area being > cleared is over 8MB seems to have fixed it. i.e.: > > else if (cpu_feature & CPUID_CLFSH) { > > to > > else if ((cpu_feature & CPUID_CLFSH) && ((eva-sva) < (2<<22))) { > > > However, I'm a little blurry on if everything leading to this point is > correct. It's ending up with 256MB of memory for the pci area, which seems > really excessive. Is the problem just that it wants room for 256 busses, > or...? Anyone know this code path well enough to know if this is deviating > from the norm?
I think that the idea not to for CLFLUSH in the loop for large regions is good. We do not extract the L2/L3 cache size now, I suppose that 2MB estimation is good for most situations. commit bbac1632d349d68b905df644656ce9a8e4aed094 Author: Konstantin Belousov <kos...@pooma.home> Date: Wed Mar 10 13:07:51 2010 +0200 Fall back to wbinvd when region for CLFLUSH is >= 2MB. Submitted by: Kevin Day <toa...@dragondata.com> diff --git a/sys/amd64/amd64/pmap.c b/sys/amd64/amd64/pmap.c index 07db5d1..4361be0 100644 --- a/sys/amd64/amd64/pmap.c +++ b/sys/amd64/amd64/pmap.c @@ -994,7 +994,8 @@ pmap_invalidate_cache_range(vm_offset_t sva, vm_offset_t eva) if (cpu_feature & CPUID_SS) ; /* If "Self Snoop" is supported, do nothing. */ - else if (cpu_feature & CPUID_CLFSH) { + else if ((cpu_feature & CPUID_CLFSH) != 0 && + eva - sva < 2 * 1024 * 1024) { /* * Otherwise, do per-cache line flush. Use the mfence @@ -1011,7 +1012,8 @@ pmap_invalidate_cache_range(vm_offset_t sva, vm_offset_t eva) /* * No targeted cache flush methods are supported by CPU, - * globally invalidate cache as a last resort. + * or the supplied range is bigger then 2MB. + * Globally invalidate cache. */ pmap_invalidate_cache(); } diff --git a/sys/i386/i386/pmap.c b/sys/i386/i386/pmap.c index 4b2e34f..f448071 100644 --- a/sys/i386/i386/pmap.c +++ b/sys/i386/i386/pmap.c @@ -996,7 +996,8 @@ pmap_invalidate_cache_range(vm_offset_t sva, vm_offset_t eva) if (cpu_feature & CPUID_SS) ; /* If "Self Snoop" is supported, do nothing. */ - else if (cpu_feature & CPUID_CLFSH) { + else if ((cpu_feature & CPUID_CLFSH) != 0 && + eva - sva < 2 * 1024 * 1024) { /* * Otherwise, do per-cache line flush. Use the mfence @@ -1013,7 +1014,8 @@ pmap_invalidate_cache_range(vm_offset_t sva, vm_offset_t eva) /* * No targeted cache flush methods are supported by CPU, - * globally invalidate cache as a last resort. + * or the supplied range is bigger then 2MB. + * Globally invalidate cache. */ pmap_invalidate_cache(); }
pgpo01y8142ck.pgp
Description: PGP signature