Messages in this thread | | | Subject | Re: sched_clock - microblaze | From | Wu Zhangjin <> | Date | Fri, 16 Apr 2010 02:12:59 +0800 |
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On Thu, 2010-04-15 at 18:32 +0200, Michal Simek wrote: > 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); > }
Hey, I guess you got:
sched_clock() -> printk() -> sched_clock() ...
since printk() is not annotated with notrace, it will call mcount() and then sched_clock() and ... so, you can not call printk() in sched_clock().
but you may try this if you want to print something in sched_clock() for debugging.
#include <>
sched_clock() { ftrace_stop(); printk(...); ftrace_start(); ... }
Regards, Wu Zhangjin
> > (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 >
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