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authorPaul Mackerras <paulus@samba.org>2010-08-26 19:56:43 +0000
committerBenjamin Herrenschmidt <benh@kernel.crashing.org>2010-09-02 14:07:31 +1000
commitcf9efce0ce3136fa076f53e53154e98455229514 (patch)
tree0e110018b160aff4813b81e0e8c3a43a364edd48 /arch/powerpc/include/asm/ppc_asm.h
parent93c22703efa72c7527dbd586d1951c1f4a85fd70 (diff)
downloadlinaro-lsk-cf9efce0ce3136fa076f53e53154e98455229514.tar.gz
powerpc: Account time using timebase rather than PURR
Currently, when CONFIG_VIRT_CPU_ACCOUNTING is enabled, we use the PURR register for measuring the user and system time used by processes, as well as other related times such as hardirq and softirq times. This turns out to be quite confusing for users because it means that a program will often be measured as taking less time when run on a multi-threaded processor (SMT2 or SMT4 mode) than it does when run on a single-threaded processor (ST mode), even though the program takes longer to finish. The discrepancy is accounted for as stolen time, which is also confusing, particularly when there are no other partitions running. This changes the accounting to use the timebase instead, meaning that the reported user and system times are the actual number of real-time seconds that the program was executing on the processor thread, regardless of which SMT mode the processor is in. Thus a program will generally show greater user and system times when run on a multi-threaded processor than on a single-threaded processor. On pSeries systems on POWER5 or later processors, we measure the stolen time (time when this partition wasn't running) using the hypervisor dispatch trace log. We check for new entries in the log on every entry from user mode and on every transition from kernel process context to soft or hard IRQ context (i.e. when account_system_vtime() gets called). So that we can correctly distinguish time stolen from user time and time stolen from system time, without having to check the log on every exit to user mode, we store separate timestamps for exit to user mode and entry from user mode. On systems that have a SPURR (POWER6 and POWER7), we read the SPURR in account_system_vtime() (as before), and then apportion the SPURR ticks since the last time we read it between scaled user time and scaled system time according to the relative proportions of user time and system time over the same interval. This avoids having to read the SPURR on every kernel entry and exit. On systems that have PURR but not SPURR (i.e., POWER5), we do the same using the PURR rather than the SPURR. This disables the DTL user interface in /sys/debug/kernel/powerpc/dtl for now since it conflicts with the use of the dispatch trace log by the time accounting code. Signed-off-by: Paul Mackerras <paulus@samba.org> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Diffstat (limited to 'arch/powerpc/include/asm/ppc_asm.h')
-rw-r--r--arch/powerpc/include/asm/ppc_asm.h50
1 files changed, 31 insertions, 19 deletions
diff --git a/arch/powerpc/include/asm/ppc_asm.h b/arch/powerpc/include/asm/ppc_asm.h
index 498fe09263d..98210067c1c 100644
--- a/arch/powerpc/include/asm/ppc_asm.h
+++ b/arch/powerpc/include/asm/ppc_asm.h
@@ -9,6 +9,7 @@
#include <asm/asm-compat.h>
#include <asm/processor.h>
#include <asm/ppc-opcode.h>
+#include <asm/firmware.h>
#ifndef __ASSEMBLY__
#error __FILE__ should only be used in assembler files
@@ -26,17 +27,13 @@
#ifndef CONFIG_VIRT_CPU_ACCOUNTING
#define ACCOUNT_CPU_USER_ENTRY(ra, rb)
#define ACCOUNT_CPU_USER_EXIT(ra, rb)
+#define ACCOUNT_STOLEN_TIME
#else
#define ACCOUNT_CPU_USER_ENTRY(ra, rb) \
beq 2f; /* if from kernel mode */ \
-BEGIN_FTR_SECTION; \
- mfspr ra,SPRN_PURR; /* get processor util. reg */ \
-END_FTR_SECTION_IFSET(CPU_FTR_PURR); \
-BEGIN_FTR_SECTION; \
- MFTB(ra); /* or get TB if no PURR */ \
-END_FTR_SECTION_IFCLR(CPU_FTR_PURR); \
- ld rb,PACA_STARTPURR(r13); \
- std ra,PACA_STARTPURR(r13); \
+ MFTB(ra); /* get timebase */ \
+ ld rb,PACA_STARTTIME_USER(r13); \
+ std ra,PACA_STARTTIME(r13); \
subf rb,rb,ra; /* subtract start value */ \
ld ra,PACA_USER_TIME(r13); \
add ra,ra,rb; /* add on to user time */ \
@@ -44,19 +41,34 @@ END_FTR_SECTION_IFCLR(CPU_FTR_PURR); \
2:
#define ACCOUNT_CPU_USER_EXIT(ra, rb) \
-BEGIN_FTR_SECTION; \
- mfspr ra,SPRN_PURR; /* get processor util. reg */ \
-END_FTR_SECTION_IFSET(CPU_FTR_PURR); \
-BEGIN_FTR_SECTION; \
- MFTB(ra); /* or get TB if no PURR */ \
-END_FTR_SECTION_IFCLR(CPU_FTR_PURR); \
- ld rb,PACA_STARTPURR(r13); \
- std ra,PACA_STARTPURR(r13); \
+ MFTB(ra); /* get timebase */ \
+ ld rb,PACA_STARTTIME(r13); \
+ std ra,PACA_STARTTIME_USER(r13); \
subf rb,rb,ra; /* subtract start value */ \
ld ra,PACA_SYSTEM_TIME(r13); \
- add ra,ra,rb; /* add on to user time */ \
- std ra,PACA_SYSTEM_TIME(r13);
-#endif
+ add ra,ra,rb; /* add on to system time */ \
+ std ra,PACA_SYSTEM_TIME(r13)
+
+#ifdef CONFIG_PPC_SPLPAR
+#define ACCOUNT_STOLEN_TIME \
+BEGIN_FW_FTR_SECTION; \
+ beq 33f; \
+ /* from user - see if there are any DTL entries to process */ \
+ ld r10,PACALPPACAPTR(r13); /* get ptr to VPA */ \
+ ld r11,PACA_DTL_RIDX(r13); /* get log read index */ \
+ ld r10,LPPACA_DTLIDX(r10); /* get log write index */ \
+ cmpd cr1,r11,r10; \
+ beq+ cr1,33f; \
+ bl .accumulate_stolen_time; \
+33: \
+END_FW_FTR_SECTION_IFSET(FW_FEATURE_SPLPAR)
+
+#else /* CONFIG_PPC_SPLPAR */
+#define ACCOUNT_STOLEN_TIME
+
+#endif /* CONFIG_PPC_SPLPAR */
+
+#endif /* CONFIG_VIRT_CPU_ACCOUNTING */
/*
* Macros for storing registers into and loading registers from