Messages in this thread | | | Date | Thu, 15 Apr 2010 18:32:57 +0200 | From | Michal Simek <> | Subject | Re: sched_clock - microblaze |
| |
Steven Rostedt wrote: > On Thu, 2010-04-15 at 16:55 +0200, Michal Simek wrote: >> Hi Thomas and Steven, >> >> I would like to improve time measuring for ftrace (Log below) >> >> I looked at http://lkml.org/lkml/2009/11/16/181 >> where Thomas suggested to create sched_clock() function. >> I used the same solution as Wu proposed but it is not nice. >> >> Is unimplemented sched_clock the reason why ftrace not show fine grain time? > > Yeah, sched_clock is used by ftrace for timings, so if it only returns > jiffies, then that will, unfortunately, be the resolution of the tracer. > > I've been told that if you make a higher resolution timer for sched > clock, it will improve the scheduling in CFS.
We have two timers (in one IP). timer0 - in IRQ mode - clock event timer1 - free running up counter without IRQ - clock source
I hope that I can use timer1 in sched_clock too.
Anyway. I played with it a little bit and I also implemented microblaze specific sched_clock function (inspired by arch/arm/mach-ixp4xx/common.c)
unsigned long long notrace sched_clock(void) { printk("%s\n", __func__); cycle_t cyc = microblaze_read(NULL); struct clocksource *cs = &clocksource_microblaze; return clocksource_cyc2ns(cyc, cs->mult, cs->shift); }
(And comment sched_clock in kernel/sched_clock.c because our toolchain has the problem with weak symbols)
Recompile the kernel and then show the log_buf
<4>Ramdisk addr 0x00000003, Compiled-in FDT at 0xc0242a28 <5>Linux version 2.6.34-rc4-00053-gbc6ce8a-dirty (monstr@monstr.eu) (gcc version 4.1.2) #27 Thu Apr 15 16:38:16 CEST 2010 <6>setup_cpuinfo: initialising <6>setup_cpuinfo: Using full CPU PVR support <6>cache: wb_msr <6>setup_memory: Main mem: 0x48000000-0x50000000, size 0x08000000, klimit 0xc09c7000 <6>setup_memory: max_mapnr: 0x8000 <6>setup_memory: min_low_pfn: 0x48000 <6>setup_memory: max_low_pfn: 0x50000 <4>reserved 0 - 0x48000000-0x009c8000 <4>reserved 1 - 0x48fe0000-0x00020000 <4>reserved 2 - 0x4fffd8c8-0x00002738 <7>On node 0 totalpages: 32768 <7>free_area_init_node: node 0, pgdat c02bc70c, node_mem_map c09c8000 <7> Normal zone: 256 pages used for memmap <7> Normal zone: 32512 pages, LIFO batch:7 <4>Built 1 zonelists in Zone order, mobility grouping on. Total pages: 32512 <5>Kernel command line: console=ttyS0,115200 <6>PID hash table entries: 512 (order: -1, 2048 bytes) <6>Dentry cache hash table entries: 16384 (order: 4, 65536 bytes) <6>Inode-cache hash table entries: 8192 (order: 3, 32768 bytes) <6>Memory: 119796k/131072k available <4>sched_clock
The problem I see is that scheck_clock is used before our timer subsystem is initialized. What am I missing?
Thanks, Michal
-- Michal Simek, Ing. (M.Eng) PetaLogix - Linux Solutions for a Reconfigurable World w: www.petalogix.com p: +61-7-30090663,+42-0-721842854 f: +61-7-30090663
| |