From: Christoph Hellwig <hch@lst.de>
To: Jens Axboe <axboe@kernel.dk>
Cc: Richard Weinberger <richard@nod.at>,
Christoph Hellwig <hch@lst.de>,
linux-block@vger.kernel.org, linux-um@lists.infradead.org,
anton.ivanov@cambridgegreys.com, dwalter@google.com
Subject: Re: [PATCH, RFC] ubd: remove use of blk_rq_map_sg
Date: Wed, 17 Oct 2018 08:21:51 +0200 [thread overview]
Message-ID: <20181017062150.GA22028@lst.de> (raw)
In-Reply-To: <da877cdc-7873-30fd-fa33-72cd48419d46@kernel.dk>
On Tue, Oct 16, 2018 at 08:26:31AM -0600, Jens Axboe wrote:
> > Yes. Shall I send a patch with your suggestion or will you?
>
> Christoph should just fold it in, the bug only exists after his
> change to it.
Sorry, I missed what suggestion we had. Is that the patch form Jens
earlier?
>
> > I have one more question, in your first conversion you set queue_depth to 2.
> > How does one know this value?
> > My conversion has 64, which is more or less an educated guess... ;)
>
> 64 is most likely just fine. Some drivers rely on having 1 in flight and
> it's easier to manage to just let blk-mq take care of that. Outside of that,
> there aren't any magic values. We should probably just use BLKDEV_MAX_RQ
> for ones that don't have a specific hw limit or need.
Is a queue depth > 1 actually safe for ubd? There are some odd global
variables tracking struct io_thread_req.
next prev parent reply other threads:[~2018-10-17 6:21 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-10-15 6:56 [PATCH, RFC] ubd: remove use of blk_rq_map_sg Christoph Hellwig
2018-10-15 8:40 ` Richard Weinberger
2018-10-15 8:45 ` Christoph Hellwig
2018-10-15 19:17 ` Richard Weinberger
2018-10-15 20:42 ` Richard Weinberger
2018-10-15 20:55 ` Christoph Hellwig
2018-10-15 21:46 ` Richard Weinberger
2018-10-15 22:04 ` Jens Axboe
2018-10-15 22:44 ` Richard Weinberger
2018-10-16 2:19 ` Jens Axboe
2018-10-16 8:38 ` Richard Weinberger
2018-10-16 14:26 ` Jens Axboe
2018-10-17 6:21 ` Christoph Hellwig [this message]
2018-10-18 21:04 ` Richard Weinberger
2018-10-16 22:43 ` Richard Weinberger
2018-10-17 6:14 ` Christoph Hellwig
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