From: Michael Tokarev <mjt@tls.msk.ru>
To: Lee Merrill <lee_merrill@yahoo.com>
Cc: LKML <linux-kernel@vger.kernel.org>
Subject: Re: Jiffies jumping with the x86 HPET
Date: Tue, 17 Nov 2009 17:05:15 +0300 [thread overview]
Message-ID: <4B02AD9B.5040105@msgid.tls.msk.ru> (raw)
In-Reply-To: <768725.48321.qm@web53403.mail.re2.yahoo.com>
Lee Merrill wrote:
> We are seeing jiffies go forward occasionally, by 300 seconds, this it appears is due to the following code in the 2.6.16 kernel:
>
> mark_offset_tsc_hpet(void):
> ...
> 1 hpet_current = hpet_readl(HPET_COUNTER);
> 2 rdtsc(last_tsc_low, last_tsc_high);
> 3
> 4 /* lost tick compensation */
> 5 offset = hpet_readl(HPET_T0_CMP) - hpet_tick;
> 6 if (unlikely(((offset - hpet_last) > hpet_tick) && (hpet_last != 0))
> 7 && detect_lost_ticks) {
> 8 int lost_ticks = (offset - hpet_last) / hpet_tick;
> 9 jiffies_64 += lost_ticks;
> 10 }
> 11 hpet_last = hpet_current;
There is no such code in current (2.6.31 or even 2.6.27.y) kernel.
Both hpet support and timer/clock code received huge changes in
2.6.24+ kernels. I guess your best bet is to upgrade.
/mjt
next prev parent reply other threads:[~2009-11-17 14:15 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-11-16 23:59 Jiffies jumping with the x86 HPET Lee Merrill
2009-11-17 14:05 ` Michael Tokarev [this message]
2009-11-17 14:57 ` just2ducky1234-1
2009-11-17 22:15 ` john stultz
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