From: Jens Axboe <axboe@kernel.dk>
To: Keith Busch <keith.busch@intel.com>
Cc: "linux-block@vger.kernel.org" <linux-block@vger.kernel.org>,
"linux-nvme@lists.infradead.org" <linux-nvme@lists.infradead.org>,
Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH v2] nvme: provide fallback for discard alloc failure
Date: Wed, 12 Dec 2018 09:36:36 -0700 [thread overview]
Message-ID: <f53d0bc1-6fe0-12e5-c210-e583d71bc739@kernel.dk> (raw)
In-Reply-To: <20181212162855.GA10895@localhost.localdomain>
On 12/12/18 9:28 AM, Keith Busch wrote:
> On Wed, Dec 12, 2018 at 09:18:11AM -0700, Jens Axboe wrote:
>> When boxes are run near (or to) OOM, we have a problem with the discard
>> page allocation in nvme. If we fail allocating the special page, we
>> return busy, and it'll get retried. But since ordering is honored for
>> dispatch requests, we can keep retrying this same IO and failing. Behind
>> that IO could be requests that want to free memory, but they never get
>> the chance.
>>
>> Allocate a fixed discard page per controller for a safe fallback, and use
>> that if the initial allocation fails.
>
> Do we need to allocate this per controller? One page for the whole driver
> may be sufficient to make forward progress, right?
It should be, but that might create a shit storm if we're OOM and have
tons of drives. I think one per controller is saner, and it's dwarfed
by memory we consume anyway in static allocations.
--
Jens Axboe
WARNING: multiple messages have this Message-ID (diff)
From: axboe@kernel.dk (Jens Axboe)
Subject: [PATCH v2] nvme: provide fallback for discard alloc failure
Date: Wed, 12 Dec 2018 09:36:36 -0700 [thread overview]
Message-ID: <f53d0bc1-6fe0-12e5-c210-e583d71bc739@kernel.dk> (raw)
In-Reply-To: <20181212162855.GA10895@localhost.localdomain>
On 12/12/18 9:28 AM, Keith Busch wrote:
> On Wed, Dec 12, 2018@09:18:11AM -0700, Jens Axboe wrote:
>> When boxes are run near (or to) OOM, we have a problem with the discard
>> page allocation in nvme. If we fail allocating the special page, we
>> return busy, and it'll get retried. But since ordering is honored for
>> dispatch requests, we can keep retrying this same IO and failing. Behind
>> that IO could be requests that want to free memory, but they never get
>> the chance.
>>
>> Allocate a fixed discard page per controller for a safe fallback, and use
>> that if the initial allocation fails.
>
> Do we need to allocate this per controller? One page for the whole driver
> may be sufficient to make forward progress, right?
It should be, but that might create a shit storm if we're OOM and have
tons of drives. I think one per controller is saner, and it's dwarfed
by memory we consume anyway in static allocations.
--
Jens Axboe
next prev parent reply other threads:[~2018-12-12 16:36 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-12-12 16:18 [PATCH v2] nvme: provide fallback for discard alloc failure Jens Axboe
2018-12-12 16:18 ` Jens Axboe
2018-12-12 16:28 ` Keith Busch
2018-12-12 16:28 ` Keith Busch
2018-12-12 16:36 ` Jens Axboe [this message]
2018-12-12 16:36 ` Jens Axboe
2018-12-12 16:50 ` Keith Busch
2018-12-12 16:50 ` Keith Busch
2018-12-13 3:00 ` Sagi Grimberg
2018-12-13 3:00 ` Sagi Grimberg
2018-12-13 8:36 ` Christoph Hellwig
2018-12-13 8:36 ` Christoph Hellwig
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