From: Christoph Hellwig <hch@infradead.org>
To: Eric Wheeler <bcache@lists.ewheeler.net>
Cc: Adriano Silva <adriano_da_silva@yahoo.com.br>,
Keith Busch <kbusch@kernel.org>,
Matthias Ferdinand <bcache@mfedv.net>,
Bcache Linux <linux-bcache@vger.kernel.org>,
Coly Li <colyli@suse.de>, Christoph Hellwig <hch@infradead.org>,
"linux-block@vger.kernel.org" <linux-block@vger.kernel.org>
Subject: Re: [RFC] Add sysctl option to drop disk flushes in bcache? (was: Bcache in writes direct with fsync)
Date: Wed, 1 Jun 2022 22:26:25 -0700 [thread overview]
Message-ID: <YphKAWHfhsCKZbBs@infradead.org> (raw)
In-Reply-To: <8a95d4f-b263-5231-537d-b1f88fdd5090@ewheeler.net>
On Wed, Jun 01, 2022 at 02:11:35PM -0700, Eric Wheeler wrote:
> It looks like the NVMe works well except in 512b situations. Its
> interesting that --force-unit-access doesn't increase the latency: Perhaps
> the NVMe ignores sync flags since it knows it has a non-volatile cache.
NVMe (and other interface) SSDs generally come in two flavors:
- consumer ones have a volatile write cache and FUA/Flush has a lot of
overhead
- enterprise ones with the grossly nisnamed "power loss protection"
feature have a non-volatile write cache and FUA/Flush has no overhead
at all
If this is an enterprise drive the behavior is expected. If on the
other hand it is a cheap consumer driver chances are it just lies, which
there have been a few instances of.
next prev parent reply other threads:[~2022-06-02 5:26 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <958894243.922478.1652201375900.ref@mail.yahoo.com>
2022-05-10 16:49 ` Bcache in writes direct with fsync. Are IOPS limited? Adriano Silva
2022-05-11 6:20 ` Matthias Ferdinand
2022-05-11 12:58 ` Adriano Silva
2022-05-11 21:21 ` Matthias Ferdinand
2022-05-18 1:22 ` Eric Wheeler
2022-05-23 14:07 ` Coly Li
2022-05-26 19:15 ` Eric Wheeler
2022-05-27 17:28 ` colyli
2022-05-28 0:58 ` Eric Wheeler
2022-05-23 18:36 ` [RFC] Add sysctl option to drop disk flushes in bcache? (was: Bcache in writes direct with fsync) Eric Wheeler
2022-05-24 5:34 ` Christoph Hellwig
2022-05-24 20:14 ` Eric Wheeler
2022-05-24 20:34 ` Keith Busch
2022-05-24 21:34 ` Eric Wheeler
2022-05-25 5:20 ` Christoph Hellwig
2022-05-25 18:44 ` Eric Wheeler
2022-05-26 9:06 ` Christoph Hellwig
2022-05-28 1:52 ` Eric Wheeler
2022-05-28 3:57 ` Keith Busch
2022-05-28 4:59 ` Christoph Hellwig
2022-05-28 12:57 ` Adriano Silva
2022-05-29 3:18 ` Keith Busch
2022-05-31 19:42 ` Eric Wheeler
2022-05-31 20:22 ` Keith Busch
2022-05-31 23:04 ` Eric Wheeler
2022-06-01 0:36 ` Keith Busch
2022-06-01 18:48 ` Eric Wheeler
[not found] ` <2064546094.2440522.1653825057164@mail.yahoo.com>
[not found] ` <YpTKfHHWz27Qugi+@kbusch-mbp.dhcp.thefacebook.com>
2022-06-01 19:27 ` Adriano Silva
2022-06-01 21:11 ` Eric Wheeler
2022-06-02 5:26 ` Christoph Hellwig [this message]
2022-05-25 5:17 ` Christoph Hellwig
[not found] ` <681726005.1812841.1653564986700@mail.yahoo.com>
2022-05-26 20:20 ` Bcache in writes direct with fsync. Are IOPS limited? Adriano Silva
2022-05-26 20:28 ` Eric Wheeler
2022-05-27 4:07 ` Adriano Silva
2022-05-28 1:27 ` Eric Wheeler
2022-05-28 7:22 ` Matthias Ferdinand
2022-05-28 12:09 ` Adriano Silva
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