From: Thomas Gleixner <tglx@linutronix.de>
To: Peter Zijlstra <peterz@infradead.org>, Peter Oskolkov <posk@posk.io>
Cc: Ingo Molnar <mingo@redhat.com>,
Andrew Morton <akpm@linux-foundation.org>,
Dave Hansen <dave.hansen@linux.intel.com>,
Andy Lutomirski <luto@kernel.org>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
linux-api@vger.kernel.org, Paul Turner <pjt@google.com>,
Ben Segall <bsegall@google.com>, Peter Oskolkov <posk@google.com>,
Andrei Vagin <avagin@google.com>, Jann Horn <jannh@google.com>,
Thierry Delisle <tdelisle@uwaterloo.ca>
Subject: Re: [PATCH v0.9.1 3/6] sched/umcg: implement UMCG syscalls
Date: Fri, 26 Nov 2021 22:11:17 +0100 [thread overview]
Message-ID: <877dcuhbbe.ffs@tglx> (raw)
In-Reply-To: <20211124211927.GG721624@worktop.programming.kicks-ass.net>
On Wed, Nov 24 2021 at 22:19, Peter Zijlstra wrote:
> On Mon, Nov 22, 2021 at 01:13:24PM -0800, Peter Oskolkov wrote:
>
>> + * Timestamp: a 46-bit CLOCK_MONOTONIC timestamp, at 16ns resolution.
>
>> +static int umcg_update_state(u64 __user *state_ts, u64 *expected, u64 desired,
>> + bool may_fault)
>> +{
>> + u64 curr_ts = (*expected) >> (64 - UMCG_STATE_TIMESTAMP_BITS);
>> + u64 next_ts = ktime_get_ns() >> UMCG_STATE_TIMESTAMP_GRANULARITY;
>
> I'm still very hesitant to use ktime (fear the HPET); but I suppose it
> makes sense to use a time base that's accessible to userspace. Was
> MONOTONIC_RAW considered?
MONOTONIC_RAW is not really useful as you can't sleep on it and it won't
solve the HPET crap either.
Thanks,
tglx
next prev parent reply other threads:[~2021-11-26 21:11 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-22 21:13 [PATCH v0.9.1 0/6] sched,mm,x86/uaccess: implement User Managed Concurrency Groups Peter Oskolkov
2021-11-22 21:13 ` [PATCH v0.9.1 1/6] sched/umcg: add WF_CURRENT_CPU and externise ttwu Peter Oskolkov
2021-11-22 21:13 ` [PATCH v0.9.1 2/6] mm, x86/uaccess: add userspace atomic helpers Peter Oskolkov
2021-11-24 14:31 ` Peter Zijlstra
2021-11-22 21:13 ` [PATCH v0.9.1 3/6] sched/umcg: implement UMCG syscalls Peter Oskolkov
2021-11-24 18:36 ` kernel test robot
2021-11-24 20:08 ` Peter Zijlstra
2021-11-24 21:32 ` Peter Zijlstra
2021-11-25 17:28 ` Peter Oskolkov
2021-11-26 17:09 ` Peter Zijlstra
2021-11-26 21:08 ` Thomas Gleixner
2021-11-26 21:59 ` Peter Zijlstra
2021-11-26 22:07 ` Peter Zijlstra
2021-11-27 0:45 ` Thomas Gleixner
2021-11-29 15:05 ` Peter Zijlstra
2021-11-26 22:16 ` Peter Zijlstra
2021-11-27 1:16 ` Thomas Gleixner
2021-11-29 15:07 ` Peter Zijlstra
2021-11-29 0:29 ` Peter Oskolkov
2021-11-29 16:41 ` Peter Zijlstra
2021-11-29 17:34 ` Peter Oskolkov
2021-11-29 21:08 ` Peter Zijlstra
2021-11-29 21:29 ` Peter Zijlstra
2021-11-29 23:38 ` Peter Oskolkov
2021-12-06 11:32 ` Peter Zijlstra
2021-12-06 12:04 ` Peter Zijlstra
2021-12-13 13:55 ` Peter Zijlstra
2021-12-06 11:47 ` Peter Zijlstra
2022-01-19 17:26 ` Peter Oskolkov
2022-01-20 11:07 ` Peter Zijlstra
2021-11-24 21:19 ` Peter Zijlstra
2021-11-26 21:11 ` Thomas Gleixner [this message]
2021-11-26 21:52 ` Peter Zijlstra
2021-11-29 22:07 ` Thomas Gleixner
2021-11-29 22:22 ` Peter Zijlstra
2021-11-24 21:41 ` Peter Zijlstra
2021-11-24 21:58 ` Peter Zijlstra
2021-11-24 22:18 ` Peter Zijlstra
2021-11-22 21:13 ` [PATCH v0.9.1 4/6] sched/umcg, lib/umcg: implement libumcg Peter Oskolkov
2021-11-22 21:13 ` [PATCH v0.9.1 5/6] sched/umcg: add Documentation/userspace-api/umcg.txt Peter Oskolkov
2021-11-22 21:13 ` [PATCH v0.9.1 6/6] sched/umcg, lib/umcg: add tools/lib/umcg/libumcg.txt Peter Oskolkov
2021-11-24 14:06 ` [PATCH v0.9.1 0/6] sched,mm,x86/uaccess: implement User Managed Concurrency Groups Peter Zijlstra
2021-11-24 16:28 ` Peter Oskolkov
2021-11-24 17:20 ` Peter Zijlstra
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