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Date: Fri, 9 May 2008 08:18:05 -0700 (PDT) From: Martin Knoblauch <knobi@...bisoft.de> To: Thomas Gleixner <tglx@...utronix.de> Cc: Gabriel C <nix.or.die@...glemail.com>, Bart Van Assche <bart.vanassche@...il.com>, linux-kernel@...r.kernel.org, hmh@....eng.br Subject: Re: 2.6.25.2 - Jiffies/Time jumping back and forth (Regereesion from 2.6.24) ----- Original Message ---- > From: Martin Knoblauch <spamtrap@...bisoft.de> > To: Thomas Gleixner <tglx@...utronix.de> > Cc: Gabriel C <nix.or.die@...glemail.com>; Bart Van Assche <bart.vanassche@...il.com>; linux-kernel@...r.kernel.org; hmh@....eng.br > Sent: Friday, May 9, 2008 3:01:10 PM > Subject: Re: 2.6.25.2 - Jiffies/Time jumping back and forth (Regereesion from 2.6.24) > > ----- Original Message ---- > > > From: Thomas Gleixner > > To: Martin Knoblauch > > Cc: Gabriel C ; Bart Van Assche > ; linux-kernel@...r.kernel.org; hmh@....eng.br > > Sent: Thursday, May 8, 2008 4:13:55 PM > > Subject: Re: 2.6.25.2 - Jiffies/Time jumping back and forth (Regereesion from > 2.6.24) > > > > On Thu, 8 May 2008, Martin Knoblauch wrote: > > > on two different systems running 2.6.25.2: > > > > > > ibm x3650(2xDualCore) > > > ------------------------------------- > > > [root@...dm60 ~]# cat > > /sys/devices/system/clocksource/clocksource0/available_clocksource > > > tsc hpet acpi_pm jiffies > > > [root@...dm60 ~]# cat > > /sys/devices/system/clocksource/clocksource0/current_clocksource > > > tsc > > > > > > HP Proliant DL-380G4 (2xSingleCore) > > > ------------------------------------------------------------ > > > [root@...dm52 ~]# cat > > /sys/devices/system/clocksource/clocksource0/available_clocksource > > > tsc hpet acpi_pm jiffies > > > [root@...dm52 ~]# cat > > /sys/devices/system/clocksource/clocksource0/current_clocksource > > > tsc > > > > > > and on the DL380G4 running 2.6.24: > > > --------------------------------------------------------- > > > [root@...dm52 ~]# cat > > /sys/devices/system/clocksource/clocksource0/available_clocksource > > > hpet acpi_pm jiffies tsc > > > [root@...dm52 ~]# cat > > /sys/devices/system/clocksource/clocksource0/current_clocksource > > > hpet > > > > So on 2.6.24 the TSC is declared unstable at some point and 2.6.25 > > thinks it works fine. Is this the same kernel config (aside of the 24/25 fuzz) > ? > > > > Thanks, > > tglx > > hah. I love open source :-) > > Between 2.6.24 and 2.6.25 there was some patching in "kernel/printk.c". > Especially this is interesting: > > > @@ -680,7 +742,7 @@ > loglev_char = default_message_loglevel > + '0'; > } > - t = printk_clock(); > + t = cpu_clock(printk_cpu); > nanosec_rem = do_div(t, 1000000000); > tlen = sprintf(tbuf, > "<%c>[%5lu.%06lu] ", > > > Where "prink_clock()" basically translates into "sched_clock()" in 2.6.24. If I > change the 2.6.25 version to directly call "sched_clock()", the timestamps are > back to the expected values and are no longer jumping back and forth. So, > something in "cpu_clock()" is fishy. > so, I added the "/printk_cpu#" to the printk timestamp. It seems that the jumping is depends on which CPU is used in the call to cpu_clock(). They seem to run at different speeds. [ 0.000000/0] TSC calibrated against PM_TIMER [ 0.000003/0] time.c: Detected 2327.507 MHz processor. [ 0.002112/0] Console: colour VGA+ 80x25 [ 0.002119/0] console [tty0] enabled [ 0.002147/0] Lock dependency validator: Copyright (c) 2006 Red Hat, Inc., Ingo Molnar [ 0.002148/0] ... MAX_LOCKDEP_SUBCLASSES: 8 [ 0.002149/0] ... MAX_LOCK_DEPTH: 48 [ 0.002151/0] ... MAX_LOCKDEP_KEYS: 2048 [ 0.002152/0] ... CLASSHASH_SIZE: 1024 [ 0.002153/0] ... MAX_LOCKDEP_ENTRIES: 8192 [ 0.002154/0] ... MAX_LOCKDEP_CHAINS: 16384 [ 0.002156/0] ... CHAINHASH_SIZE: 8192 [ 0.002157/0] memory used by lock dependency info: 1712 kB [ 0.002158/0] per task-struct memory footprint: 3456 bytes [ 0.002161/0] Checking aperture... [ 0.002170/0] PCI-DMA: Using software bounce buffering for IO (SWIOTLB) [ 0.004000/0] Placing software IO TLB between 0x15093000 - 0x19093000 [ 0.004000/0] Memory: 8110260k/9437184k available (2945k kernel code, 277728k reserved, 1568k data, 796k init) [ 0.004000/0] CPA: page pool initialized 1 of 1 pages preallocated [ 0.004000/0] hpet clockevent registered [ 0.080008/0] Calibrating delay using timer specific routine.. 4660.35 BogoMIPS (lpj=9320712) [ 0.080104/0] Security Framework initialized [ 0.080110/0] SELinux: Initializing. [ 0.080150/0] SELinux: Starting in permissive mode [ 0.080157/0] selinux_register_security: Registering secondary module capability [ 0.080159/0] Capability LSM initialized as secondary [ 0.080904/0] Dentry cache hash table entries: 1048576 (order: 11, 8388608 bytes) [ 0.085951/0] Inode-cache hash table entries: 524288 (order: 10, 4194304 bytes) [ 0.088684/0] Mount-cache hash table entries: 256 [ 0.089128/0] CPU: L1 I cache: 32K, L1 D cache: 32K [ 0.089130/0] CPU: L2 cache: 4096K [ 0.089133/0] CPU 0/0 -> Node 0 [ 0.089135/0] CPU: Physical Processor ID: 0 [ 0.089136/0] CPU: Processor Core ID: 0 [ 0.089142/0] CPU0: Thermal monitoring enabled (TM2) [ 0.089144/0] using mwait in idle threads. [ 0.089152/0] Freeing SMP alternatives: 22k freed [ 0.089171/0] ACPI: Core revision 20070126 [ 0.135354/0] Using local APIC timer interrupts. [ 0.136010/0] APIC timer calibration result 20781297 [ 0.136012/0] Detected 20.781 MHz APIC timer. [ 0.136435/0] lockdep: fixing up alternatives. [ 0.136478/0] Booting processor 1/4 APIC 0x1 [ 0.004000/1] Initializing CPU#1 [ 0.004000/1] Calibrating delay using timer specific routine.. 4655.08 BogoMIPS (lpj=9310168) [ 0.004000/1] CPU: L1 I cache: 32K, L1 D cache: 32K [ 0.004000/1] CPU: L2 cache: 4096K [ 0.004000/1] CPU 1/1 -> Node 0 [ 0.004000/1] CPU: Physical Processor ID: 0 [ 0.004000/1] CPU: Processor Core ID: 1 [ 0.004000/1] CPU1: Thermal monitoring enabled (TM2) [ 0.004000/1] Intel(R) Xeon(R) CPU 5140 @ 2.33GHz stepping 06 [ 0.224558/0] checking TSC synchronization [CPU#0 -> CPU#1]: passed. [ 0.228357/0] lockdep: fixing up alternatives. [ 0.228392/0] Booting processor 2/4 APIC 0x6 [ 0.004000/2] Initializing CPU#2 [ 0.004000/2] Calibrating delay using timer specific routine.. 4655.12 BogoMIPS (lpj=9310252) [ 0.004000/2] CPU: L1 I cache: 32K, L1 D cache: 32K [ 0.004000/2] CPU: L2 cache: 4096K [ 0.004000/2] CPU 2/6 -> Node 0 [ 0.004000/2] CPU: Physical Processor ID: 3 [ 0.004000/2] CPU: Processor Core ID: 0 [ 0.004000/2] CPU2: Thermal monitoring enabled (TM2) [ 0.004000/2] Intel(R) Xeon(R) CPU 5140 @ 2.33GHz stepping 06 [ 0.316632/0] checking TSC synchronization [CPU#0 -> CPU#2]: passed. [ 0.320292/0] lockdep: fixing up alternatives. [ 0.320325/0] Booting processor 3/4 APIC 0x7 [ 0.004000/3] Initializing CPU#3 [ 0.004000/3] Calibrating delay using timer specific routine.. 4655.13 BogoMIPS (lpj=9310270) [ 0.004000/3] CPU: L1 I cache: 32K, L1 D cache: 32K [ 0.004000/3] CPU: L2 cache: 4096K [ 0.004000/3] CPU 3/7 -> Node 0 [ 0.004000/3] CPU: Physical Processor ID: 3 [ 0.004000/3] CPU: Processor Core ID: 1 [ 0.004000/3] CPU3: Thermal monitoring enabled (TM2) [ 0.004000/3] Intel(R) Xeon(R) CPU 5140 @ 2.33GHz stepping 06 [ 0.408625/0] checking TSC synchronization [CPU#0 -> CPU#3]: passed. [ 0.412054/0] Brought up 4 CPUs [ 0.412168/0] CPU0 attaching sched-domain: [ 0.412170/0] domain 0: span 03 [ 0.412172/0] groups: 01 02 [ 0.412175/0] domain 1: span 0f [ 0.412176/0] groups: 03 0c [ 0.412179/0] domain 2: span 0f -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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