lkml.org 
[lkml]   [2020]   [Jan]   [13]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
Subject[RFC PATCH v3 00/12] powerpc: switch VDSO to C implementation.
Date
This is a third tentative to switch powerpc VDSO to generic C implementation.

This version should work on PPC64 (untested). VDSO32 for PPC64 is
impossible to build and has been de-activated, because the powerpc
ASM header files for C are not prepared to build 32 bits code with CONFIG_PPC64.

powerpc is a bit special for VDSO as well as system calls in the
way that it requires setting CR SO bit which cannot be done in C.
Therefore, entry/exit and fallback need to be performed in ASM.

On a powerpc8xx, with current powerpc/32 ASM VDSO:

gettimeofday: vdso: 737 nsec/call
clock-getres-realtime: vdso: 475 nsec/call
clock-gettime-realtime: vdso: 892 nsec/call

The first patch adds VDSO generic C support without any changes to common code.
Performance is as follows:

gettimeofday: vdso: 1379 nsec/call
clock-getres-realtime-coarse: vdso: 984 nsec/call
clock-gettime-realtime-coarse: vdso: 868 nsec/call
clock-getres-realtime: vdso: 922 nsec/call
clock-gettime-realtime: vdso: 1511 nsec/call
clock-getres-monotonic-raw: vdso: 968 nsec/call
clock-gettime-monotonic-raw: vdso: 1576 nsec/call

Then a few changes in the common code have allowed performance improvement. At
the end of the series we have:

gettimeofday: vdso: 899 nsec/call
clock-getres-realtime-coarse: vdso: 546 nsec/call
clock-gettime-realtime-coarse: vdso: 615 nsec/call
clock-getres-realtime: vdso: 545 nsec/call
clock-gettime-realtime: vdso: 1064 nsec/call
clock-getres-monotonic-raw: vdso: 546 nsec/call
clock-gettime-monotonic-raw: vdso: 1125 nsec/call

Christophe Leroy (12):
powerpc/64: Don't provide time functions in compat VDSO32
powerpc/vdso: Switch VDSO to generic C implementation.
lib: vdso: mark __cvdso_clock_getres() as static
lib: vdso: inline do_hres() and do_coarse()
lib: vdso: Avoid duplication in __cvdso_clock_getres()
lib: vdso: __iter_div_u64_rem() is suboptimal for 32 bit time
powerpc/vdso: simplify __get_datapage()
lib: vdso: allow arches to provide vdso data pointer
powerpc/vdso: provide inline alternative to __get_datapage()
powerpc/vdso: provide vdso data pointer from the ASM caller.
lib: vdso: split clock verification out of __arch_get_hw_counter()
powerpc/vdso: provide __arch_is_hw_counter_valid()

arch/powerpc/Kconfig | 2 +
arch/powerpc/include/asm/vdso/gettimeofday.h | 104 +++++++++++
arch/powerpc/include/asm/vdso/vsyscall.h | 25 +++
arch/powerpc/include/asm/vdso_datapage.h | 52 +++---
arch/powerpc/kernel/asm-offsets.c | 46 +----
arch/powerpc/kernel/time.c | 90 ----------
arch/powerpc/kernel/vdso.c | 58 ++----
arch/powerpc/kernel/vdso32/Makefile | 30 +++-
arch/powerpc/kernel/vdso32/datapage.S | 10 +-
arch/powerpc/kernel/vdso32/gettimeofday.S | 258 ++++-----------------------
arch/powerpc/kernel/vdso32/vdso32.lds.S | 9 +-
arch/powerpc/kernel/vdso32/vgettimeofday.c | 29 +++
arch/powerpc/kernel/vdso64/Makefile | 23 ++-
arch/powerpc/kernel/vdso64/datapage.S | 13 +-
arch/powerpc/kernel/vdso64/gettimeofday.S | 257 ++++----------------------
arch/powerpc/kernel/vdso64/vdso64.lds.S | 7 +-
arch/powerpc/kernel/vdso64/vgettimeofday.c | 29 +++
lib/vdso/gettimeofday.c | 130 +++++++++++---
18 files changed, 457 insertions(+), 715 deletions(-)
create mode 100644 arch/powerpc/include/asm/vdso/gettimeofday.h
create mode 100644 arch/powerpc/include/asm/vdso/vsyscall.h
create mode 100644 arch/powerpc/kernel/vdso32/vgettimeofday.c
create mode 100644 arch/powerpc/kernel/vdso64/vgettimeofday.c

--
2.13.3

\
 
 \ /
  Last update: 2020-01-13 18:09    [W:0.102 / U:5.456 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site