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Re: [PATCH] [15/58] i386: Rewrite sched_clock

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From: Andi Kleen
Subject: Re: [PATCH] [15/58] i386: Rewrite sched_clock
Date: Friday, July 20, 2007 - 8:14 am

> So if, after this, we run tsc_sched_clock() with an unstable TSC, we

On x86-64 the 64bit write is atomic against interrupts.

You're right 32bit has a problem though. I'm not too happy about 
cmpxchg though because that wouldn't work on some CPUs.

I wonder if we can just get away with using a 32bit value on i386.
Just for the purpose of keeping the value monotonic it should be good
enough. Will think about it.

Thanks for the review.

-Andi

-
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[PATCH] [0/58] First batch of x86 patches for .23, Andi Kleen, (Thu Jul 19, 2:54 am)
[PATCH] [1/58] x86: Always flush pages in change_page_attr, Andi Kleen, (Thu Jul 19, 2:54 am)
[PATCH] [2/58] x86_64: Tell gcc to only align stack to 8 bytes, Andi Kleen, (Thu Jul 19, 2:54 am)
[PATCH] [3/58] x86_64: asm/ptrace.h needs linux/compiler.h, Andi Kleen, (Thu Jul 19, 2:54 am)
[PATCH] [4/58] x86_64: Don't rely on a unique IO-APIC ID, Andi Kleen, (Thu Jul 19, 2:54 am)
[PATCH] [5/58] x86_64: Report the pending irq if available ..., Andi Kleen, (Thu Jul 19, 2:54 am)
[PATCH] [6/58] x86_64: Use LOCAL_DISTANCE and REMOTE_DIST ..., Andi Kleen, (Thu Jul 19, 2:54 am)
[PATCH] [7/58] x86_64: various cleanups in NUMA scan node, Andi Kleen, (Thu Jul 19, 2:54 am)
[PATCH] [8/58] x86_64: Use string instruction memcpy/memse ..., Andi Kleen, (Thu Jul 19, 2:54 am)
[PATCH] [9/58] x86_64: Always use builtin memcpy on gcc 4.3, Andi Kleen, (Thu Jul 19, 2:54 am)
[PATCH] [10/58] i386: Move all simple string operations ou ..., Andi Kleen, (Thu Jul 19, 2:54 am)
[PATCH] [11/58] x86: Support __attribute__((__cold__)) in ..., Andi Kleen, (Thu Jul 19, 2:54 am)
[PATCH] [12/58] x86_64: Add vDSO for x86-64 with gettimeof ..., Andi Kleen, (Thu Jul 19, 2:54 am)
[PATCH] [13/58] x86: Separate checking of unsynchronized a ..., Andi Kleen, (Thu Jul 19, 2:54 am)
[PATCH] [14/58] x86_64: Add on_cpu_single, Andi Kleen, (Thu Jul 19, 2:54 am)
[PATCH] [15/58] i386: Rewrite sched_clock, Andi Kleen, (Thu Jul 19, 2:54 am)
[PATCH] [16/58] x86_64: Use new shared sched_clock in x86- ..., Andi Kleen, (Thu Jul 19, 2:55 am)
[PATCH] [17/58] i386: Add L3 cache support to AMD CPUID4 e ..., Andi Kleen, (Thu Jul 19, 2:55 am)
[PATCH] [18/58] x86_64: remove extra extern declaring abou ..., Andi Kleen, (Thu Jul 19, 2:55 am)
[PATCH] [19/58] x86_64: Don't use softirq save locks in sm ..., Andi Kleen, (Thu Jul 19, 2:55 am)
[PATCH] [20/58] x86: Always probe the NMI watchdog, Andi Kleen, (Thu Jul 19, 2:55 am)
[PATCH] [21/58] i386: Reserve the right performance counte ..., Andi Kleen, (Thu Jul 19, 2:55 am)
[PATCH] [22/58] x86_64: hpet tsc calibration fix broken sm ..., Andi Kleen, (Thu Jul 19, 2:55 am)
[PATCH] [23/58] i386: remove pit_interrupt_hook, Andi Kleen, (Thu Jul 19, 2:55 am)
[PATCH] [24/58] x86_64: Untangle asm/hpet.h from asm/timex.h, Andi Kleen, (Thu Jul 19, 2:55 am)
[PATCH] [25/58] x86_64: use generic cmos update, Andi Kleen, (Thu Jul 19, 2:55 am)
[PATCH] [26/58] x86_64: Use generic xtime init, Andi Kleen, (Thu Jul 19, 2:55 am)
[PATCH] [27/58] x86_64: Remove dead code and other janitor ..., Andi Kleen, (Thu Jul 19, 2:55 am)
[PATCH] [28/58] x86_64: Fix APIC typo, Andi Kleen, (Thu Jul 19, 2:55 am)
[PATCH] [29/58] x86_64: fiuxp pt_reqs leftovers, Andi Kleen, (Thu Jul 19, 2:55 am)
[PATCH] [30/58] x86: share hpet.h with i386, Andi Kleen, (Thu Jul 19, 2:55 am)
[PATCH] [31/58] x86_64: apic.c coding style janitor work, Andi Kleen, (Thu Jul 19, 2:55 am)
[PATCH] [32/58] x86_64: time.c white space wreckage cleanup, Andi Kleen, (Thu Jul 19, 2:55 am)
[PATCH] [33/58] x86_64: Avoid too many remote cpu referenc ..., Andi Kleen, (Thu Jul 19, 2:55 am)
[PATCH] [34/58] x86_64: ia32entry adjustments, Andi Kleen, (Thu Jul 19, 2:55 am)
[PATCH] [35/58] i386: allow debuggers to access the vsysca ..., Andi Kleen, (Thu Jul 19, 2:55 am)
[PATCH] [36/58] x86_64: minor exception trace variables cl ..., Andi Kleen, (Thu Jul 19, 2:55 am)
[PATCH] [37/58] x86_64: remove unused variable maxcpus, Andi Kleen, (Thu Jul 19, 2:55 am)
[PATCH] [38/58] i386: smp-alt-once option is only useful w ..., Andi Kleen, (Thu Jul 19, 2:55 am)
[PATCH] [39/58] i386: minor nx handling adjustment, Andi Kleen, (Thu Jul 19, 2:55 am)
[PATCH] [40/58] i386: remapped_pgdat_init() static, Andi Kleen, (Thu Jul 19, 2:55 am)
[PATCH] [41/58] i386: arch/i386/kernel/i8253.c should #inc ..., Andi Kleen, (Thu Jul 19, 2:55 am)
[PATCH] [42/58] i386: timer_irq_works() static again, Andi Kleen, (Thu Jul 19, 2:55 am)
[PATCH] [43/58] x86_64: Quicklist support for x86_64, Andi Kleen, (Thu Jul 19, 2:55 am)
[PATCH] [44/58] x86_64: extract helper function from e820_ ..., Andi Kleen, (Thu Jul 19, 2:55 am)
[PATCH] [45/58] x86_64: fake pxm-to-node mapping for fake numa, Andi Kleen, (Thu Jul 19, 2:55 am)
[PATCH] [46/58] x86_64: fake apicid_to_node mapping for fa ..., Andi Kleen, (Thu Jul 19, 2:55 am)
[PATCH] [47/58] i386: insert unclaimed MMCONFIG resources, Andi Kleen, (Thu Jul 19, 2:55 am)
[PATCH] [48/58] x86_64: O_EXCL on /dev/mcelog, Andi Kleen, (Thu Jul 19, 2:55 am)
[PATCH] [49/58] x86_64: support poll() on /dev/mcelog, Andi Kleen, (Thu Jul 19, 2:55 am)
[PATCH] [50/58] x86_64: mcelog tolerant level cleanup, Andi Kleen, (Thu Jul 19, 2:55 am)
[PATCH] [51/58] i386: fix machine rebooting, Andi Kleen, (Thu Jul 19, 2:55 am)
[PATCH] [52/58] i386: fix section mismatch warnings in mtrr, Andi Kleen, (Thu Jul 19, 2:55 am)
[PATCH] [53/58] x86: PM_TRACE support, Andi Kleen, (Thu Jul 19, 2:55 am)
[PATCH] [54/58] x86: Make Alt-SysRq-p display the debug re ..., Andi Kleen, (Thu Jul 19, 2:55 am)
[PATCH] [55/58] i386: add reference to the arguments, Andi Kleen, (Thu Jul 19, 2:55 am)
[PATCH] [56/58] x86: round_jiffies() for i386 and x86-64 n ..., Andi Kleen, (Thu Jul 19, 2:55 am)
[PATCH] [57/58] x86_64: check remote IRR bit before migrat ..., Andi Kleen, (Thu Jul 19, 2:55 am)
[PATCH] [58/58] x86: remove support for the Rise CPU, Andi Kleen, (Thu Jul 19, 2:55 am)
Re: [PATCH] [21/58] i386: Reserve the right performance co ..., Björn, (Thu Jul 19, 3:21 am)
Re: [PATCH] [33/58] x86_64: Avoid too many remote cpu refe ..., Christoph Hellwig, (Thu Jul 19, 3:21 am)
Re: [PATCH] [5/58] x86_64: Report the pending irq if avail ..., Ingo Molnar, (Thu Jul 19, 3:23 am)
Re: [PATCH] [20/58] x86: Always probe the NMI watchdog, Björn, (Thu Jul 19, 3:24 am)
Re: [PATCH] [33/58] x86_64: Avoid too many remote cpu refe ..., Andi Kleen, (Thu Jul 19, 3:41 am)
Re: [PATCH] [20/58] x86: Always probe the NMI watchdog, Andi Kleen, (Thu Jul 19, 3:42 am)
Re: [PATCH] [21/58] i386: Reserve the right performance co ..., Andi Kleen, (Thu Jul 19, 3:45 am)
Re: [PATCH] [58/58] x86: remove support for the Rise CPU, Alan Cox, (Thu Jul 19, 3:45 am)
Re: [PATCH] [58/58] x86: remove support for the Rise CPU, Adrian Bunk, (Thu Jul 19, 3:48 am)
Re: [PATCH] [33/58] x86_64: Avoid too many remote cpu refe ..., Adrian Bunk, (Thu Jul 19, 3:55 am)
Re: [PATCH] [14/58] x86_64: Add on_cpu_single, Satyam Sharma, (Thu Jul 19, 4:09 am)
Re: [PATCH] [58/58] x86: remove support for the Rise CPU, Alan Cox, (Thu Jul 19, 4:13 am)
Re: [PATCH] [2/58] x86_64: Tell gcc to only align stack to ..., Serge Belyshev, (Thu Jul 19, 4:50 am)
Re: [PATCH] [58/58] x86: remove support for the Rise CPU, Andi Kleen, (Thu Jul 19, 5:03 am)
Re: [PATCH] [2/58] x86_64: Tell gcc to only align stack to ..., Andi Kleen, (Thu Jul 19, 5:06 am)
Re: [PATCH] [14/58] x86_64: Add on_cpu_single, Andi Kleen, (Thu Jul 19, 5:07 am)
Re: [PATCH] [19/58] x86_64: Don't use softirq save locks i ..., Satyam Sharma, (Thu Jul 19, 5:16 am)
Re: [PATCH] [19/58] x86_64: Don't use softirq save locks i ..., Andi Kleen, (Thu Jul 19, 5:19 am)
Re: [PATCH] [2/58] x86_64: Tell gcc to only align stack to ..., Chuck Ebbert, (Thu Jul 19, 7:42 am)
Re: [PATCH] [34/58] x86_64: ia32entry adjustments, Jeff Garzik, (Thu Jul 19, 7:46 am)
Re: [PATCH] [58/58] x86: remove support for the Rise CPU, Jeff Garzik, (Thu Jul 19, 7:56 am)
Re: [PATCH] [8/58] x86_64: Use string instruction memcpy/m ..., Jan Engelhardt, (Thu Jul 19, 9:43 am)
Re: [PATCH] [15/58] i386: Rewrite sched_clock, Daniel Walker, (Thu Jul 19, 9:51 am)
Re: [PATCH] [8/58] x86_64: Use string instruction memcpy/m ..., Yinghai Lu, (Thu Jul 19, 10:00 am)
Re: [PATCH] [15/58] i386: Rewrite sched_clock, Andi Kleen, (Thu Jul 19, 10:13 am)
Re: [PATCH] [15/58] i386: Rewrite sched_clock, Daniel Walker, (Thu Jul 19, 10:15 am)
Re: [PATCH] [7/58] x86_64: various cleanups in NUMA scan node, Yinghai Lu, (Thu Jul 19, 10:15 am)
Re: [PATCH] [7/58] x86_64: various cleanups in NUMA scan node, Andi Kleen, (Thu Jul 19, 10:21 am)
Re: [PATCH] [15/58] i386: Rewrite sched_clock, Andi Kleen, (Thu Jul 19, 10:22 am)
Re: [PATCH] [15/58] i386: Rewrite sched_clock, Daniel Walker, (Thu Jul 19, 10:31 am)
Re: [PATCH] [7/58] x86_64: various cleanups in NUMA scan node, Yinghai Lu, (Thu Jul 19, 10:38 am)
Re: [PATCH] [15/58] i386: Rewrite sched_clock, Andi Kleen, (Thu Jul 19, 10:38 am)
Re: [PATCH] [15/58] i386: Rewrite sched_clock, Daniel Walker, (Thu Jul 19, 10:43 am)
Re: [PATCH] [15/58] i386: Rewrite sched_clock, Daniel Walker, (Thu Jul 19, 11:00 am)
Re: [PATCH] [15/58] i386: Rewrite sched_clock, Andi Kleen, (Thu Jul 19, 11:00 am)
Re: [PATCH] [7/58] x86_64: various cleanups in NUMA scan node, Andi Kleen, (Thu Jul 19, 1:00 pm)
Re: [PATCH] [7/58] x86_64: various cleanups in NUMA scan node, David Rientjes, (Thu Jul 19, 2:01 pm)
Re: [PATCH] [15/58] i386: Rewrite sched_clock, Mathieu Desnoyers, (Thu Jul 19, 8:11 pm)
Re: [PATCH] [15/58] i386: Rewrite sched_clock, Mathieu Desnoyers, (Thu Jul 19, 8:47 pm)
Re: [PATCH] [15/58] i386: Rewrite sched_clock (cmpxchg8b), Mathieu Desnoyers, (Thu Jul 19, 9:18 pm)
Re: [PATCH] [15/58] i386: Rewrite sched_clock (cmpxchg8b), Nick Piggin, (Thu Jul 19, 10:07 pm)
Re: [PATCH] [15/58] i386: Rewrite sched_clock (cmpxchg8b), Mathieu Desnoyers, (Thu Jul 19, 10:47 pm)
Re: [PATCH] [15/58] i386: Rewrite sched_clock, Andi Kleen, (Fri Jul 20, 1:27 am)
Re: [PATCH] [15/58] i386: Rewrite sched_clock, Mathieu Desnoyers, (Fri Jul 20, 7:12 am)
Re: [PATCH] [15/58] i386: Rewrite sched_clock, Mathieu Desnoyers, (Fri Jul 20, 7:39 am)
Re: [PATCH] [15/58] i386: Rewrite sched_clock, Andi Kleen, (Fri Jul 20, 8:14 am)
Re: [PATCH] [15/58] i386: Rewrite sched_clock, Mathieu Desnoyers, (Fri Jul 20, 8:22 am)
[PATCH] 80386 and 80486 cmpxchg64 and cmpxchg64_local fallback, Mathieu Desnoyers, (Fri Jul 20, 9:49 am)
Re: [patches] [PATCH] [17/58] i386: Add L3 cache support t ..., Andreas Herrmann, (Fri Jul 20, 10:00 am)
Re: [patches] [PATCH] [17/58] i386: Add L3 cache support t ..., Andreas Herrmann, (Fri Jul 20, 10:15 am)
Re: [PATCH] [9/58] x86_64: Always use builtin memcpy on gc ..., Oleg Verych, (Sat Jul 21, 4:16 pm)
Re: [PATCH] [9/58] x86_64: Always use builtin memcpy on gc ..., Andi Kleen, (Sat Jul 21, 4:27 pm)
Re: [PATCH] [9/58] x86_64: Always use builtin memcpy on gc ..., Denis Vlasenko, (Sat Jul 21, 5:29 pm)
Re: [patches] [PATCH] [1/58] x86: Always flush pages in ch ..., Jan Beulich, (Mon Aug 6, 3:15 am)
Re: [patches] [PATCH] [1/58] x86: Always flush pages in ch ..., Andi Kleen, (Mon Aug 6, 3:36 am)
Re: [PATCH] [34/58] x86_64: ia32entry adjustments, Jan Beulich, (Mon Aug 6, 3:43 am)
Re: [patches] [PATCH] [1/58] x86: Always flush pages in ch ..., Jan Beulich, (Mon Aug 6, 3:49 am)
Re: [PATCH] [12/58] x86_64: Add vDSO for x86-64 with getti ..., Daniel Walker, (Tue Aug 21, 9:25 am)
Re: [PATCH] [12/58] x86_64: Add vDSO for x86-64 with getti ..., Andrew Morton, (Tue Aug 21, 11:40 am)
Re: [PATCH] [12/58] x86_64: Add vDSO for x86-64 with getti ..., Andi Kleen, (Tue Aug 21, 11:45 am)