[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <CA+55aFw7t++BzEy-XsatNcauw3Wn22SSXfd3iTYECi4fJ97CCg@mail.gmail.com>
Date: Thu, 19 Jul 2018 08:08:20 -0700
From: Linus Torvalds <torvalds@...ux-foundation.org>
To: Peter Zijlstra <peterz@...radead.org>
Cc: Johannes Weiner <hannes@...xchg.org>,
Ingo Molnar <mingo@...hat.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Tejun Heo <tj@...nel.org>, surenb@...gle.com,
Vinayak Menon <vinmenon@...eaurora.org>,
Christoph Lameter <cl@...ux.com>,
Mike Galbraith <efault@....de>, shakeelb@...gle.com,
linux-mm <linux-mm@...ck.org>, cgroups <cgroups@...r.kernel.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
kernel-team <kernel-team@...com>
Subject: Re: [PATCH 08/10] psi: pressure stall information for CPU, memory,
and IO
On Wed, Jul 18, 2018 at 5:03 AM Peter Zijlstra <peterz@...radead.org> wrote:
>
> And as said before, we can compress the state from 12 bytes, to 6 bits
> (or 1 byte), giving another 11 bytes for 59 bytes free.
>
> Leaving us just 5 bytes short of needing a single cacheline :/
Do you actually need 64 bits for the times?
That's the big cost. And it seems ridiculous, if you actually care about size.
You already have a 64-bit start time. Everything else is some
cumulative relative time. Do those really need 64-bit and nanosecond
resolution?
Maybe a 32-bit microsecond would be ok - would you ever account more
than 35 minutes of anything without starting anew?
Linus
Powered by blists - more mailing lists