Commit Graph

20 Commits

Author SHA1 Message Date
David S. Miller
dcc1e8dd88 [SPARC64]: Add a secondary TSB for hugepage mappings.
Signed-off-by: David S. Miller <davem@davemloft.net>
2006-03-22 01:15:14 -08:00
David S. Miller
bb8646d834 [SPARC64]: Optimized TSB table initialization.
We only need to write an invalid tag every 16 bytes,
so taking advantage of this can save many instructions
compared to the simple memset() call we make now.

A prefetching implementation is implemented for sun4u
and a block-init store version if implemented for Niagara.

The next trick is to be able to perform an init and
a copy_tsb() in parallel when growing a TSB table.

Signed-off-by: David S. Miller <davem@davemloft.net>
2006-03-20 01:16:41 -08:00
David S. Miller
9b4006dcf6 [SPARC64]: Use SLAB caches for TSB tables.
Signed-off-by: David S. Miller <davem@davemloft.net>
2006-03-20 01:16:39 -08:00
David S. Miller
b52439c22c [SPARC64]: Don't kill the page allocator when growing a TSB.
Try only lightly on > 1 order allocations.

If a grow fails, we are under memory pressure, so do not try
to grow the TSB for this address space any more.

If a > 0 order TSB allocation fails on a new fork, retry using
a 0 order allocation.

Signed-off-by: David S. Miller <davem@davemloft.net>
2006-03-20 01:16:38 -08:00
David S. Miller
7a1ac52641 [SPARC64]: Fix and re-enable dynamic TSB sizing.
This is good for up to %50 performance improvement of some test cases.
The problem has been the race conditions, and hopefully I've plugged
them all up here.

1) There was a serious race in switch_mm() wrt. lazy TLB
   switching to and from kernel threads.

   We could erroneously skip a tsb_context_switch() and thus
   use a stale TSB across a TSB grow event.

   There is a big comment now in that function describing
   exactly how it can happen.

2) All code paths that do something with the TSB need to be
   guarded with the mm->context.lock spinlock.  This makes
   page table flushing paths properly synchronize with both
   TSB growing and TLB context changes.

3) TSB growing events are moved to the end of successful fault
   processing.  Previously it was in update_mmu_cache() but
   that is deadlock prone.  At the end of do_sparc64_fault()
   we hold no spinlocks that could deadlock the TSB grow
   sequence.  We also have dropped the address space semaphore.

While we're here, add prefetching to the copy_tsb() routine
and put it in assembler into the tsb.S file.  This piece of
code is quite time critical.

There are some small negative side effects to this code which
can be improved upon.  In particular we grab the mm->context.lock
even for the tsb insert done by update_mmu_cache() now and that's
a bit excessive.  We can get rid of that locking, and the same
lock taking in flush_tsb_user(), by disabling PSTATE_IE around
the whole operation including the capturing of the tsb pointer
and tsb_nentries value.  That would work because anyone growing
the TSB won't free up the old TSB until all cpus respond to the
TSB change cross call.

I'm not quite so confident in that optimization to put it in
right now, but eventually we might be able to and the description
is here for reference.

This code seems very solid now.  It passes several parallel GCC
bootstrap builds, and our favorite "nut cruncher" stress test which is
a full "make -j8192" build of a "make allmodconfig" kernel.  That puts
about 256 processes on each cpu's run queue, makes lots of process cpu
migrations occur, causes lots of page table and TLB flushing activity,
incurs many context version number changes, and it swaps the machine
real far out to disk even though there is 16GB of ram on this test
system. :-)

Signed-off-by: David S. Miller <davem@davemloft.net>
2006-03-20 01:16:33 -08:00
David S. Miller
a77754b4d0 [SPARC64]: Bulletproof MMU context locking.
1) Always spin_lock_init() in init_context().  The caller essentially
   clears it out, or copies the mm info from the parent.  In both
   cases we need to explicitly initialize the spinlock.

2) Always do explicit IRQ disabling while taking mm->context.lock
   and ctx_alloc_lock.

Signed-off-by: David S. Miller <davem@davemloft.net>
2006-03-20 01:14:20 -08:00
David S. Miller
77b838fa1e [SPARC64]: destroy_context() needs to disable interrupts.
get_new_mmu_context() can be invoked from interrupt context
now for the new SMP version wrap handling.

So disable interrupt while taking ctx_alloc_lock in destroy_context()
so we don't deadlock.

Signed-off-by: David S. Miller <davem@davemloft.net>
2006-03-20 01:14:01 -08:00
David S. Miller
8b23427441 [SPARC64]: More TLB/TSB handling fixes.
The SUN4V convention with non-shared TSBs is that the context
bit of the TAG is clear.  So we have to choose an "invalid"
bit and initialize new TSBs appropriately.  Otherwise a zero
TAG looks "valid".

Make sure, for the window fixup cases, that we use the right
global registers and that we don't potentially trample on
the live global registers in etrap/rtrap handling (%g2 and
%g6) and that we put the missing virtual address properly
in %g5.

Signed-off-by: David S. Miller <davem@davemloft.net>
2006-03-20 01:13:34 -08:00
David S. Miller
de635d833f [SPARC64]: Fix flush_tsb_user() on SUN4V.
Needs to use physical addressing just like cheetah_plus.

Signed-off-by: David S. Miller <davem@davemloft.net>
2006-03-20 01:13:07 -08:00
David S. Miller
c4bce90ea2 [SPARC64]: Deal with PTE layout differences in SUN4V.
Yes, you heard it right, they changed the PTE layout for
SUN4V.  Ho hum...

This is the simple and inefficient way to support this.
It'll get optimized, don't worry.

Signed-off-by: David S. Miller <davem@davemloft.net>
2006-03-20 01:12:25 -08:00
David S. Miller
e92b92571c [SPARC64]: Handle hypervisor case correctly in copy_tsb().
Signed-off-by: David S. Miller <davem@davemloft.net>
2006-03-20 01:12:19 -08:00
David S. Miller
618e9ed98a [SPARC64]: Hypervisor TSB context switching.
Signed-off-by: David S. Miller <davem@davemloft.net>
2006-03-20 01:12:06 -08:00
David S. Miller
f4e841da30 [SPARC64]: Turn off TSB growing for now.
There are several tricky races involved with growing the TSB.  So just
use base-size TSBs for user contexts and we can revisit enabling this
later.

One part of the SMP problems is that tsb_context_switch() can see
partially updated TSB configuration state if tsb_grow() is running in
parallel.  That's easily solved with a seqlock taken as a writer by
tsb_grow() and taken as a reader to capture all the TSB config state
in tsb_context_switch().

Then there is flush_tsb_user() running in parallel with a tsb_grow().
In theory we could take the seqlock as a reader there too, and just
resample the TSB pointer and reflush but that looks really ugly.

Lastly, I believe there is a case with threads that results in a TSB
entry lock bit being set spuriously which will cause the next access
to that TSB entry to wedge the cpu (since the TSB entry lock bit will
never clear).  It's either copy_tsb() or some bug elsewhere in the TSB
assembly.

Signed-off-by: David S. Miller <davem@davemloft.net>
2006-03-20 01:11:34 -08:00
David S. Miller
517af33237 [SPARC64]: Access TSB with physical addresses when possible.
This way we don't need to lock the TSB into the TLB.
The trick is that every TSB load/store is registered into
a special instruction patch section.  The default uses
virtual addresses, and the patch instructions use physical
address load/stores.

We can't do this on all chips because only cheetah+ and later
have the physical variant of the atomic quad load.

Signed-off-by: David S. Miller <davem@davemloft.net>
2006-03-20 01:11:32 -08:00
David S. Miller
2f7ee7c63f [SPARC64]: Increase swapper_tsb size to 32K.
Signed-off-by: David S. Miller <davem@davemloft.net>
2006-03-20 01:11:26 -08:00
David S. Miller
4753eb2ac7 [SPARC64]: Fix incorrect TSB lock bit handling.
The TSB_LOCK_BIT define is actually a special
value shifted down by 32-bits for the assembler
code macros.

In C code, this isn't what we want.

Signed-off-by: David S. Miller <davem@davemloft.net>
2006-03-20 01:11:21 -08:00
David S. Miller
bd40791e1d [SPARC64]: Dynamically grow TSB in response to RSS growth.
As the RSS grows, grow the TSB in order to reduce the likelyhood
of hash collisions and thus poor hit rates in the TSB.

This definitely needs some serious tuning.

Signed-off-by: David S. Miller <davem@davemloft.net>
2006-03-20 01:11:18 -08:00
David S. Miller
98c5584cfc [SPARC64]: Add infrastructure for dynamic TSB sizing.
This also cleans up tsb_context_switch().  The assembler
routine is now __tsb_context_switch() and the former is
an inline function that picks out the bits from the mm_struct
and passes it into the assembler code as arguments.

setup_tsb_parms() computes the locked TLB entry to map the
TSB.  Later when we support using the physical address quad
load instructions of Cheetah+ and later, we'll simply use
the physical address for the TSB register value and set
the map virtual and PTE both to zero.

Signed-off-by: David S. Miller <davem@davemloft.net>
2006-03-20 01:11:17 -08:00
David S. Miller
09f94287f7 [SPARC64]: TSB refinements.
Move {init_new,destroy}_context() out of line.

Do not put huge pages into the TSB, only base page size translations.
There are some clever things we could do here, but for now let's be
correct instead of fancy.

Signed-off-by: David S. Miller <davem@davemloft.net>
2006-03-20 01:11:16 -08:00
David S. Miller
74bf4312ff [SPARC64]: Move away from virtual page tables, part 1.
We now use the TSB hardware assist features of the UltraSPARC
MMUs.

SMP is currently knowingly broken, we need to find another place
to store the per-cpu base pointers.  We hid them away in the TSB
base register, and that obviously will not work any more :-)

Another known broken case is non-8KB base page size.

Also noticed that flush_tlb_all() is not referenced anywhere, only
the internal __flush_tlb_all() (local cpu only) is used by the
sparc64 port, so we can get rid of flush_tlb_all().

The kernel gets it's own 8KB TSB (swapper_tsb) and each address space
gets it's own private 8K TSB.  Later we can add code to dynamically
increase the size of per-process TSB as the RSS grows.  An 8KB TSB is
good enough for up to about a 4MB RSS, after which the TSB starts to
incur many capacity and conflict misses.

We even accumulate OBP translations into the kernel TSB.

Another area for refinement is large page size support.  We could use
a secondary address space TSB to handle those.

Signed-off-by: David S. Miller <davem@davemloft.net>
2006-03-20 01:11:13 -08:00