From: Eric Dumazet <eric.dumazet@gmail.com>
To: Arun Sharma <asharma@fb.com>
Cc: linux-kernel@vger.kernel.org, Kumar Sundararajan <kumar@fb.com>,
Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@elte.hu>, Thomas Gleixner <tglx@linutronix.de>,
john stultz <johnstul@us.ibm.com>, Andy Lutomirski <luto@MIT.EDU>
Subject: Re: [PATCH 2/2] Add a thread cpu time implementation to vDSO
Date: Mon, 12 Dec 2011 22:27:23 +0100 [thread overview]
Message-ID: <1323725243.2583.27.camel@edumazet-laptop> (raw)
In-Reply-To: <4EE66FE9.1050202@fb.com>
Le lundi 12 décembre 2011 à 13:19 -0800, Arun Sharma a écrit :
> On 12/12/11 12:13 PM, Eric Dumazet wrote:
>
> >> +
> >> +struct vcpu_data {
> >> + struct vpercpu_data vpercpu[NR_CPUS];
> >> + unsigned int tsc_khz;
> >> + unsigned int tsc_unstable;
> >> +};
> >
> > Thats a showstopper.
> >
> > Try to compile the thing with NR_CPUS=4096 ?
> >
>
> I get a link time error:
>
> ld: section .data..percpu [0000000001ac2000 -> 0000000001ad48ff]
> overlaps section .vvar [0000000001ac0000 -> 0000000001b0083f]
>
> which I consider better than runtime memory corruption :)
>
> I could add a BUILD_BUG_ON() that tries to catch this earlier in the
> compile process.
>
> Re: Fixing the build for NR_CPUS > 64
>
> How about something along the lines of the following:
>
> From: Arun Sharma <asharma@fb.com>
> Date: Mon, 12 Dec 2011 13:13:43 -0800
> Subject: [PATCH] Handle NR_CPUS > 64
>
> ---
This only works if CONFIG_X86_L1_CACHE_SHIFT=6
Some configurations have 128 bytes cache lines
But really most modern distros have NR_CPUS > 64
next prev parent reply other threads:[~2011-12-12 21:27 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-12-12 19:36 [PATCH 0/2] " Arun Sharma
2011-12-12 19:36 ` [PATCH 1/2] Extend VVAR support to multiple pages Arun Sharma
2011-12-12 19:36 ` [PATCH 2/2] Add a thread cpu time implementation to vDSO Arun Sharma
2011-12-12 20:13 ` Eric Dumazet
2011-12-12 21:19 ` Arun Sharma
2011-12-12 21:27 ` Eric Dumazet [this message]
2011-12-12 21:33 ` Andrew Lutomirski
2011-12-12 22:14 ` Arun Sharma
2011-12-13 8:52 ` Peter Zijlstra
2011-12-13 18:15 ` Arun Sharma
2011-12-13 18:53 ` Peter Zijlstra
2011-12-12 20:15 ` Andrew Lutomirski
2011-12-12 22:49 ` Arun Sharma
2011-12-12 23:01 ` Andrew Lutomirski
2011-12-13 0:40 ` Arun Sharma
2011-12-12 23:09 ` john stultz
2011-12-12 23:20 ` Arun Sharma
2011-12-12 23:32 ` john stultz
2011-12-12 23:41 ` Andrew Lutomirski
2011-12-12 23:52 ` john stultz
2011-12-13 0:26 ` Arun Sharma
2011-12-19 19:51 [PATCH 0/2] Add a thread cpu time implementation to vDSO (v2) Arun Sharma
2011-12-19 19:51 ` [PATCH 2/2] Add a thread cpu time implementation to vDSO Arun Sharma
2011-12-19 19:58 ` Arun Sharma
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