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Improvements come from eliminating srlz.i, not scheduling AR/CR-reads
too early (while there are others still pending), scheduling the
backing-store switch as well as possible, splitting the BBB bundle
into a MIB/MBB pair.
Why is it safe to eliminate the srlz.i? Observe
that we used to clear bits ~PSR_PRESERVED_BITS in PSR.L. Since
PSR_PRESERVED_BITS==PSR.{UP,MFL,MFH,PK,DT,PP,SP,RT,IC}, we
ended up clearing PSR.{BE,AC,I,DFL,DFH,DI,DB,SI,TB}. However,
PSR.BE : already is turned off in __kernel_syscall_via_epc()
PSR.AC : don't care (kernel normally turns PSR.AC on)
PSR.I : already turned off by the time fsys_bubble_down gets invoked
PSR.DFL: always 0 (kernel never turns it on)
PSR.DFH: don't care --- kernel never touches f32-f127 on its own
initiative
PSR.DI : always 0 (kernel never turns it on)
PSR.SI : always 0 (kernel never turns it on)
PSR.DB : don't care --- kernel never enables kernel-level breakpoints
PSR.TB : must be 0 already; if it wasn't zero on entry to
__kernel_syscall_via_epc, the branch to fsys_bubble_down
will trigger a taken branch; the taken-trap-handler then
converts the syscall into a break-based system-call.
In other words: all the bits we're clearying are either 0 already or
are don't cares! Thus, we don't have to write PSR.L at all and we
don't have to do a srlz.i either.
Good for another ~20 cycle improvement for EPC-based heavy-weight
syscalls.
Signed-off-by: David Mosberger-Tang <davidm@hpl.hp.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
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Two other very minor changes: use "mov.i" instead of "mov" for reading
ar.pfs (for clarity; doesn't affect the code at all). Also, predicate
the load of r14 for consistency.
Signed-off-by: David Mosberger-Tang <davidm@hpl.hp.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
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Avoid some stalls, which is good for about 2 cycles when invoking a
light-weight handler. When invoking a heavy-weight handler, this
helps by about 7 cycles, with most of the improvement coming from the
improved branch-prediction achieved by splitting the BBB bundle into
two MIB bundles.
Signed-off-by: David Mosberger-Tang <davidm@hpl.hp.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
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This patch reorganizes break_fault() to optimistically assume that a
system-call is being performed from user-space (which is almost always
the case). If it turns out that (a) we're not being called due to a
system call or (b) we're being called from within the kernel, we fixup
the no-longer-valid assumptions in non_syscall() and .break_fixup(),
respectively.
With this approach, there are 3 major phases:
- Phase 1: Read various control & application registers, in
particular the current task pointer from AR.K6.
- Phase 2: Do all memory loads (load system-call entry,
load current_thread_info()->flags, prefetch
kernel register-backing store) and switch
to kernel register-stack.
- Phase 3: Call ia64_syscall_setup() and invoke
syscall-handler.
Good for 26-30 cycles of improvement on break-based syscall-path.
Signed-off-by: David Mosberger-Tang <davidm@hpl.hp.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
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Signed-off-by: David Mosberger-Tang <davidm@hpl.hp.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
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Reschedule code to read ar.bsp as early as possible. To enable this,
don't bother clearing some of the registers when we're returning to
kernel stacks. Also, instead of trying to support the pNonSys case
(which makes no sense), do a bugcheck instead (with break 0). Finally,
remove a clear of r14 which is a left-over from the previous patch.
Signed-off-by: David Mosberger-Tang <davidm@hpl.hp.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
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Using stf8 seemed like a clever idea at the time, but stf8 forces
the cache-line to be invalidated in the L1D (if it happens to be
there already). This patch eliminates a guaranteed L1D cache-miss
and, by itself, is good for a 1-2 cycle improvement for heavy-weight
syscalls.
Signed-off-by: David Mosberger-Tang <davidm@hpl.hp.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
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Why is this a good idea? Clearing b7 to 0 is guaranteed to do us no
good and writing it with __kernel_syscall_via_epc() yields a 6 cycle
improvement _if_ the application performs another EPC-based system-
call without overwriting b7, which is not all that uncommon. Well
worth the minimal cost of 1 bundle of code.
Signed-off-by: David Mosberger-Tang <davidm@hpl.hp.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
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Decreases syscall overhead by approximately 6 cycles.
Signed-off-by: David Mosberger-Tang <davidm@hpl.hp.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
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This by itself is good for a 1-2 cycle speed up. Effect is bigger
when combined with the later patches.
Signed-off-by: David Mosberger-Tang <davidm@hpl.hp.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
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Signed-off-by: David Mosberger-Tang <davidm@hpl.hp.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
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vector sharing patch had a typo ... mismatched spin_lock() with
a spin_unlock_irq(). Fix from Kenji Kaneshige.
Signed-off-by: Tony Luck <tony.luck@intel.com>
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Rohit and Suresh changed their mind about the order to print things
in /proc/cpuinfo, but didn't include the change in the version of
the patch they sent to me.
Signed-off-by: Tony Luck <tony.luck@intel.com>
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Current ia64 linux cannot handle greater than 184 interrupt sources
because of the lack of vectors. The following patch enables ia64 linux
to handle greater than 184 interrupt sources by allowing the same
vector number to be shared by multiple IOSAPIC's RTEs. The design of
this patch is besed on "Intel(R) Itanium(R) Processor Family Interrupt
Architecture Guide".
Even if you don't have a large I/O system, you can see the behavior of
vector sharing by changing IOSAPIC_LAST_DEVICE_VECTOR to fewer value.
Signed-off-by: Kenji Kaneshige <kaneshige.kenji@jp.fujitsu.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
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Version 3 - rediffed to apply on top of Ashok's hotplug cpu
patch. /proc/cpuinfo output in step with x86.
This is an updated MC/MT identification patch based on the
previous discussions on list.
Add the Multi-core and Multi-threading detection for IPF.
- Add new core and threading related fields in /proc/cpuinfo.
Physical id
Core id
Thread id
Siblings
- setup the cpu_core_map and cpu_sibling_map appropriately
- Handles Hot plug CPU
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: Gordon Jin <gordon.jin@intel.com>
Signed-off-by: Rohit Seth <rohit.seth@intel.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
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Sadly, I goofed in this syscall-tuning patch:
ChangeSet 1.1966.1.40 2005/01/22 13:31:05 davidm@hpl.hp.com
[IA64] Improve ia64_leave_syscall() for McKinley-type cores.
Optimize ia64_leave_syscall() a bit better for McKinley-type cores.
The patch looks big, but that's mostly due to renaming r16/r17 to r2/r3.
Good for a 13 cycle improvement.
The problem is that the size of the physical stacked registers was
loaded into the wrong register (r3 instead of r17). Since r17 by
coincidence always had the value 1, this had the effect of turning
rse_clear_invalid into a no-op. That poses the risk of leaking kernel
state back to user-land and is hence not acceptable.
The fix below is simple, but unfortunately it costs us about 28 cycles
in syscall overhead. ;-(
Unfortunately, there isn't much we can do about that since those
registers have to be cleared one way or another.
--david
Signed-off-by: Tony Luck <tony.luck@intel.com>
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- make pfm_sysctl a global such that it is possible
to enable/disable debug printk in sampling formats
using PFM_DEBUG.
- remove unused pfm_debug_var variable
- fix a bug in pfm_handle_work where an BUG_ON() could
be triggered. There is a path where pfm_handle_work()
can be called with interrupts enabled, i.e., when
TIF_NEED_RESCHED is set. The fix correct the masking
and unmasking of interrupts in pfm_handle_work() such
that we restore the interrupt mask as it was upon entry.
signed-off-by: stephane eranian <eranian@hpl.hp.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
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Recently I noticed that clearing ar.ssd/ar.csd right before srlz.d is
causing significant stalling in the syscall path. The patch below
fixes that by moving the register-writes after srlz.d. On a Madison,
this drops break-based getpid() from 241 to 226 cycles (-15 cycles).
Signed-off-by: David Mosberger-Tang <davidm@hpl.hp.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
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Detect user space by the unwind frame with predicate PRED_USER_STACK
set, instead of a user space IP. Tighten up the last ditch check for
running off the top of the kernel stack.
Based on a suggestion by David Mosberger, reworked to fit the current
tree. This survives my stress test which used to break 2.6.9 kernels.
Unlike 2.6.11, the stress test now unwinds to the correct point, so
gdb can get the user space registers.
Signed-off-by: Keith Owens <kaos@sgi.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
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Call cpu_relax() in busy-waiting loops of the ITC-syncing code.
Signed-off-by: David Mosberger-Tang <davidm@hpl.hp.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
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Signed-off-by: Ashok Raj <ashok.raj@intel.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
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This patch is required to support cpu removal for IPF systems. Existing code
just fakes the real offline by keeping it run the idle thread, and polling
for the bit to re-appear in the cpu_state to get out of the idle loop.
For the cpu-offline to work correctly, we need to pass control of this CPU
back to SAL so it can continue in the boot-rendez mode. This gives the
SAL control to not pick this cpu as the monarch processor for global MCA
events, and addition does not wait for this cpu to checkin with SAL
for global MCA events as well. The handoff is implemented as documented in
SAL specification section 3.2.5.1 "OS_BOOT_RENDEZ to SAL return State"
Signed-off-by: Ashok Raj <ashok.raj@intel.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
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Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.
Let it rip!
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David Mosberger-Tang
Kenji Kaneshige
Tony Luck
Suresh Siddha
Stephane Eranian
Keith Owens
Ashok Raj
Linus Torvalds