From: Thomas Gleixner <tglx@linutronix.de>
To: speck@linutronix.de
Subject: Re: Additional sampling fun
Date: Fri, 28 Feb 2020 18:44:48 +0100 [thread overview]
Message-ID: <87zhd2fvxr.fsf@nanos.tec.linutronix.de> (raw)
In-Reply-To: <20200228173845.GA2466@mtg-dev.jf.intel.com>
speck for mark gross <speck@linutronix.de> writes:
> On Fri, Feb 28, 2020 at 05:34:47PM +0100, speck for Greg KH wrote:
>> On Fri, Feb 28, 2020 at 05:21:40PM +0100, speck for Borislav Petkov wrote:
>> Ugh. I think we need to drag Jason into this as well, but really,
>> talking about that can be done on the mailing list as there's nothing
>> wrong with trying to get that slow code out of the irq path today,
>> right?
>>
> FWIW unless someone is abusing rdrand/rdseed I don't think the impact of the
> mitigation will be measurable. Running multiple instances of spanking rdrand
> in a loop will show nonlinear impacts due to bus lock contention but, I don't
> think there is any contention issues with once/64IRS's or once a second. you
> are looking at approximately O(100cycles) vrs O(1000cycles) every second or
> every 64th interrupt. I don't think you'll be able to measure the impact of
> that. (unless you force lock contention on the HW bus lock)
Have several cores with a 10k+ interrupts per second and if you're
unlucky they start to contend, then the every 64th interrupt will be
measurable quite prominent.
But I agree with Greg, that we can tackle this on LKML without
mentioning that particular issue.
Thanks,
tglx
next prev parent reply other threads:[~2020-02-28 17:44 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-19 22:45 [MODERATED] [PATCH 0/2] more sampling fun 0 mark gross
2020-02-20 1:53 ` [MODERATED] " mark gross
2020-02-20 8:14 ` Greg KH
2020-02-20 14:27 ` Greg KH
2020-02-20 15:40 ` mark gross
2020-02-20 16:18 ` Greg KH
2020-02-20 14:55 ` Andi Kleen
2020-02-20 15:05 ` Greg KH
2020-02-20 16:55 ` Andi Kleen
2020-02-20 21:51 ` Josh Poimboeuf
2020-02-20 22:15 ` Andi Kleen
2020-02-20 22:59 ` Kees Cook
2020-02-20 15:09 ` mark gross
2020-02-28 16:21 ` [MODERATED] Additional sampling fun Borislav Petkov
2020-02-28 16:34 ` [MODERATED] " Greg KH
2020-02-28 17:38 ` mark gross
2020-02-28 17:44 ` Thomas Gleixner [this message]
2020-02-28 18:09 ` Luck, Tony
2020-02-28 18:40 ` Borislav Petkov
2020-02-28 21:53 ` Thomas Gleixner
2020-03-03 1:03 ` [MODERATED] " Luck, Tony
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