linux-kernel - Re: [PATCH 2/2] Use ktime_get() instead of sched

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Sat, 12 Jun 2010 08:51:54 -0700
From:	Divyesh Shah <dpshah@...gle.com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	jaxboe@...ionio.com, peterz@...radead.org, piotr@...owicz.com,
	linux-kernel@...r.kernel.org, vgoyal@...hat.com,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH 2/2] Use ktime_get() instead of sched_clock() for blkio 
	cgroup stats.

On Sat, Jun 12, 2010 at 12:18 AM, Ingo Molnar <mingo@...e.hu> wrote:
>
> * Divyesh Shah <dpshah@...gle.com> wrote:
>
>> This will take care of the pre-emptive kernel issue and the unbounded
>> TSC drift problem. We will lose resolution though in some cases.
>
>> -     blkg->stats.start_group_wait_time = sched_clock();
>> +     blkg->stats.start_group_wait_time = ktime_to_ns(ktime_get());
>
> Ugh!
>
> ktime_get() can have insanely high overhead. Peter has added local_clock(), if
> then you should use that and apply checks to make sure the result isnt
> negative.

Ok. The negative checks are already in the code.

>
>        Ingo
>
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/