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From: Kanchan Joshi <joshiiitr@gmail.com>
To: "hch@infradead.org" <hch@infradead.org>
Cc: Damien Le Moal <Damien.LeMoal@wdc.com>,
	Jens Axboe <axboe@kernel.dk>,
	Pavel Begunkov <asml.silence@gmail.com>,
	Kanchan Joshi <joshi.k@samsung.com>,
	"viro@zeniv.linux.org.uk" <viro@zeniv.linux.org.uk>,
	"bcrl@kvack.org" <bcrl@kvack.org>,
	Matthew Wilcox <willy@infradead.org>,
	"linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"linux-aio@kvack.org" <linux-aio@kvack.org>,
	"io-uring@vger.kernel.org" <io-uring@vger.kernel.org>,
	"linux-block@vger.kernel.org" <linux-block@vger.kernel.org>,
	"linux-api@vger.kernel.org" <linux-api@vger.kernel.org>,
	SelvaKumar S <selvakuma.s1@samsung.com>,
	Nitesh Shetty <nj.shetty@samsung.com>,
	Javier Gonzalez <javier.gonz@samsung.com>,
	Johannes Thumshirn <Johannes.Thumshirn@wdc.com>,
	Naohiro Aota <Naohiro.Aota@wdc.com>
Subject: Re: [PATCH v4 6/6] io_uring: add support for zone-append
Date: Thu, 24 Sep 2020 22:49:28 +0530
Message-ID: <CA+1E3r+MSEW=-SL8L+pquq+cFAu+nQOULQ+HZoQsCvdjKMkrNw@mail.gmail.com> (raw)
In-Reply-To: <20200908151801.GA16742@infradead.org>

On Tue, Sep 8, 2020 at 8:48 PM hch@infradead.org <hch@infradead.org> wrote:
>
> On Mon, Sep 07, 2020 at 12:31:42PM +0530, Kanchan Joshi wrote:
> > But there are use-cases which benefit from supporting zone-append on
> > raw block-dev path.
> > Certain user-space log-structured/cow FS/DB will use the device that
> > way. Aerospike is one example.
> > Pass-through is synchronous, and we lose the ability to use io-uring.
>
> So use zonefs, which is designed exactly for that use case.

Not specific to zone-append, but in general it may not be good to lock
new features/interfaces to ZoneFS alone, given that direct-block
interface has its own merits.
Mapping one file to a one zone is good for some use-cases, but
limiting for others.
Some user-space FS/DBs would be more efficient (less meta, indirection)
with the freedom to decide file-to-zone mapping/placement.
- Rocksdb and those LSM style DBs would map SSTable to zone, but
SSTable file may be two small (initially) and may become too large
(after compaction) for a zone.
- The internal parallelism of a single zone is a design-choice, and
depends on the drive. Writing multiple zones parallely (striped/raid
way) can give better performance than writing on one. In that case one
would want to file that seamlessly combines multiple-zones in a
striped fashion.

Also it seems difficult (compared to block dev) to fit simple-copy TP
in ZoneFS. The new
command needs: one NVMe drive, list of source LBAs and one destination
LBA. In ZoneFS, we would deal with N+1 file-descriptors (N source zone
file, and one destination zone file) for that. While with block
interface, we do not need  more than one file-descriptor representing
the entire device. With more zone-files, we face open/close overhead too.

-- 
Joshi

  reply index

Thread overview: 52+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <CGME20200724155244epcas5p2902f57e36e490ee8772da19aa9408cdc@epcas5p2.samsung.com>
2020-07-24 15:49 ` [PATCH v4 0/6] zone-append support in io-uring and aio Kanchan Joshi
     [not found]   ` <CGME20200724155258epcas5p1a75b926950a18cd1e6c8e7a047e6c589@epcas5p1.samsung.com>
2020-07-24 15:49     ` [PATCH v4 1/6] fs: introduce FMODE_ZONE_APPEND and IOCB_ZONE_APPEND Kanchan Joshi
2020-07-24 16:34       ` Jens Axboe
2020-07-26 15:18       ` Christoph Hellwig
2020-07-28  1:49         ` Matthew Wilcox
2020-07-28  7:26           ` Christoph Hellwig
     [not found]   ` <CGME20200724155324epcas5p18e1d3b4402d1e4a8eca87d0b56a3fa9b@epcas5p1.samsung.com>
2020-07-24 15:49     ` [PATCH v4 2/6] fs: change ki_complete interface to support 64bit ret2 Kanchan Joshi
2020-07-26 15:18       ` Christoph Hellwig
     [not found]   ` <CGME20200724155329epcas5p345ba6bad0b8fe18056bb4bcd26c10019@epcas5p3.samsung.com>
2020-07-24 15:49     ` [PATCH v4 3/6] uio: return status with iov truncation Kanchan Joshi
     [not found]   ` <CGME20200724155341epcas5p15bfc55927f2abb60f19784270fe8e377@epcas5p1.samsung.com>
2020-07-24 15:49     ` [PATCH v4 4/6] block: add zone append handling for direct I/O path Kanchan Joshi
2020-07-26 15:19       ` Christoph Hellwig
     [not found]   ` <CGME20200724155346epcas5p2cfb383fe9904a45280c6145f4c13e1b4@epcas5p2.samsung.com>
2020-07-24 15:49     ` [PATCH v4 5/6] block: enable zone-append for iov_iter of bvec type Kanchan Joshi
2020-07-26 15:20       ` Christoph Hellwig
     [not found]   ` <CGME20200724155350epcas5p3b8f1d59eda7f8fbb38c828f692d42fd6@epcas5p3.samsung.com>
2020-07-24 15:49     ` [PATCH v4 6/6] io_uring: add support for zone-append Kanchan Joshi
2020-07-24 16:29       ` Jens Axboe
2020-07-27 19:16         ` Kanchan Joshi
2020-07-27 20:34           ` Jens Axboe
2020-07-30 16:08             ` Pavel Begunkov
2020-07-30 16:13               ` Jens Axboe
2020-07-30 16:26                 ` Pavel Begunkov
2020-07-30 17:16                   ` Jens Axboe
2020-07-30 17:38                     ` Pavel Begunkov
2020-07-30 17:51                       ` Kanchan Joshi
2020-07-30 17:54                         ` Jens Axboe
2020-07-30 18:25                           ` Kanchan Joshi
2020-07-31  6:42                             ` Damien Le Moal
2020-07-31  6:45                               ` hch
2020-07-31  6:59                                 ` Damien Le Moal
2020-07-31  7:58                                   ` Kanchan Joshi
2020-07-31  8:14                                     ` Damien Le Moal
2020-07-31  9:14                                       ` hch
2020-07-31  9:34                                         ` Damien Le Moal
2020-07-31  9:41                                           ` hch
2020-07-31 10:16                                             ` Damien Le Moal
2020-07-31 12:51                                               ` hch
2020-07-31 13:08                                                 ` hch
2020-07-31 15:07                                                   ` Kanchan Joshi
2020-08-05  7:35                                                 ` Damien Le Moal
2020-08-14  8:14                                                   ` hch
2020-08-14  8:27                                                     ` Damien Le Moal
2020-08-14 12:04                                                       ` hch
2020-08-14 12:20                                                         ` Damien Le Moal
2020-09-07  7:01                                                     ` Kanchan Joshi
2020-09-08 15:18                                                       ` hch
2020-09-24 17:19                                                         ` Kanchan Joshi [this message]
2020-09-25  2:52                                                           ` Damien Le Moal
2020-09-28 18:58                                                             ` Kanchan Joshi
2020-09-29  1:24                                                               ` Damien Le Moal
2020-09-29 18:49                                                                 ` Kanchan Joshi
2020-07-31  9:38                                       ` Kanchan Joshi
2020-07-31  7:08                               ` Kanchan Joshi
2020-07-30 15:57       ` Pavel Begunkov

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