lk/linux-kernel-test
1
0
Fork 0
Code Issues Pull Requests Releases Wiki Activity

MIPS: Collect FPU emulator statistics per-CPU.

Browse Source 
On SMP systems, the collection of statistics can cause cache line
bouncing in the lines associated with the counters.  Also there are
races incrementing the counters on multiple CPUs.

To fix both problems, we collect the statistics in per-CPU variables,
and add them up in the debugfs read operation.

As a test I ran the LTP float_bessel test on a 12 CPU Octeon system.

Without CONFIG_DEBUG_FS :             2602 seconds.
With CONFIG_DEBUG_FS:                 2640 seconds.
With non-cpu-local atomic statistics: 14569 seconds.

Signed-off-by: David Daney <ddaney@caviumnetworks.com>
Cc: linux-mips@linux-mips.org
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
This commit is contained in:
David Daney
2009-11-05 11:34:26 -08:00
committed by Ralf Baechle
parent 32028f1f7b
commit b6ee75ed4f
3 changed files with 80 additions and 50 deletions
Download Patch File Download Diff File Expand all files Collapse all files

4
arch/mips/math-emu/dsemul.c
View File

@@ -98,7 +98,7 @@ int mips_dsemul(struct pt_regs *regs, mips_instruction ir, unsigned long cpc)
err |= __put_user(cpc, &fr->epc);
if (unlikely(err)) {
fpuemustats.errors++;
MIPS_FPU_EMU_INC_STATS(errors);
return SIGBUS;
}
@@ -136,7 +136,7 @@ int do_dsemulret(struct pt_regs *xcp)
err |= __get_user(cookie, &fr->cookie);
if (unlikely(err || (insn != BREAK_MATH) || (cookie != BD_COOKIE))) {
fpuemustats.errors++;
MIPS_FPU_EMU_INC_STATS(errors);
return 0;
}