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Message-ID: <CALCETrUYutdtp5U7oYwf7-eNuB0MrwoC18mG5-S8iOP4ZEVDuA@mail.gmail.com>
Date: Thu, 18 May 2017 18:13:55 -0700
From: Andy Lutomirski <luto@...nel.org>
To: Andy Lutomirski <luto@...nel.org>
Cc: Jens Axboe <axboe@...nel.dk>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
Kai-Heng Feng <kai.heng.feng@...onical.com>,
linux-nvme <linux-nvme@...ts.infradead.org>,
Christoph Hellwig <hch@....de>,
Sagi Grimberg <sagi@...mberg.me>,
Keith Busch <keith.busch@...el.com>,
Mario Limonciello <mario_limonciello@...l.com>
Subject: Re: [PATCH] nvme: Change our APST table to be no more aggressive than
Intel RSTe
On Thu, May 11, 2017 at 9:06 PM, Andy Lutomirski <luto@...nel.org> wrote:
> It seems like RSTe is much more conservative with transition timing
> that we are. According to Mario, RSTe programs APST to transition from
> active states to the first idle state after 60ms and, thereafter, to
> 1000 * the exit latency of the target state.
>
I pondered this a bit, and I want to NAK my own patch. This patch
stinks -- there's mounting evidence that what it really does is to
make any problems show up more rarely. If a system is broken, I want
it to be obviously broken.
Here are two options to move forward:
a) Leave the Dell quirk in place until someone from Dell or Samsung
figures out what's actually going on. Add a blanket quirk turning off
the deepest sleep state on all Intel devices [1] at least until
someone from Intel figures out what's going on -- Hi, Keith! Deal
with any other problems as they're reported.
b) Turn off the deepest state across the board and add a whitelist.
Populate the whitelist a bit. The problem is that I don't even know
what to whitelist. My system works great, but does that mean that my
particular laptop is fine? My particular disk is certainly *not* fine
when installed in other laptops.
Ideas? (a) is a bit simpler to implement, I think, and may be good enough.
[1] There are problems on Intel NUC machines with Intel SSDs, for
crying out loud. I realize that the team that designs the NUC is
probably totally unrelated to the SSD team, but they're both Intel and
it shouldn't be *that* hard for someone at Intel to get it debugged.
See https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1686592
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