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From: Damien Le Moal <Damien.LeMoal@wdc.com>
To: "Martin K. Petersen" <martin.petersen@oracle.com>,
	Naohiro Aota <Naohiro.Aota@wdc.com>
Cc: "linux-btrfs@vger.kernel.org" <linux-btrfs@vger.kernel.org>,
	"dsterba@suse.com" <dsterba@suse.com>,
	"hare@suse.com" <hare@suse.com>,
	"linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
	Johannes Thumshirn <Johannes.Thumshirn@wdc.com>
Subject: Re: [PATCH v8 01/41] block: add bio_add_zone_append_page
Date: Mon, 5 Oct 2020 01:46:34 +0000	[thread overview]
Message-ID: <CY4PR04MB3751168260AB3888599741D9E70C0@CY4PR04MB3751.namprd04.prod.outlook.com> (raw)
In-Reply-To: yq1k0w8g3rw.fsf@ca-mkp.ca.oracle.com

On 2020/10/02 22:39, Martin K. Petersen wrote:
> 
> Naohiro/Johannes,
> 
>> Add bio_add_zone_append_page(), a wrapper around bio_add_hw_page() which
>> is intended to be used by file systems that directly add pages to a bio
>> instead of using bio_iov_iter_get_pages().
> 
> Why use the hardware limit? For filesystem I/O we generally use the
> queue soft limit to prevent I/Os getting too big which can lead to very
> unpredictable latency in mixed workloads.

max_zone_append_sectors is already gated by max_hw_sectors, but it is not gated
by max_sectors/BLK_DEF_MAX_SECTORS. If we add such gating to
blk_queue_max_zone_append_sectors(), max_zone_append_sectors would become a soft
limit too. So should we have max_zone_append_sectors and
max_hw_zone_append_sectors ?

Which also means that we should tweak queue_max_sectors_store() to gate
max_zone_append_sectors to that limit upon a user change.

> 
> max_zone_append_sectors also appears to be gated exclusively by hardware
> constraints. Is there user-controllable limit in place for append
> operations?

No, none that I know of. At the HW level, max_zone_append_sectors is basically
max_hw_sectors. That is gated by the zone size in
blk_queue_max_zone_append_sectors(). If as mentioned above we tweak
queue_max_sectors_store() to change max_zone_append_sectors too if needed, we
would then have an indirect user-controllable limit. Or we could implement a
queue_zone_append_max_store() too I guess. Yet, having everything indirectly
controlled through queue_max_sectors_store() is probably simpler I think.

-- 
Damien Le Moal
Western Digital Research

  reply	other threads:[~2020-10-05  1:46 UTC|newest]

Thread overview: 61+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-01 18:36 [PATCH v8 00/41] btrfs: zoned block device support Naohiro Aota
2020-10-01 18:36 ` [PATCH v8 01/41] block: add bio_add_zone_append_page Naohiro Aota
2020-10-01 18:36   ` [PATCH v8 02/41] btrfs: introduce ZONED feature flag Naohiro Aota
2020-10-01 18:36   ` [PATCH v8 03/41] btrfs: Get zone information of zoned block devices Naohiro Aota
2020-10-13 15:53     ` David Sterba
2020-10-15  7:45       ` Johannes Thumshirn
2020-10-01 18:36   ` [PATCH v8 04/41] btrfs: Check and enable ZONED mode Naohiro Aota
2020-10-13 15:56     ` David Sterba
2020-10-28 14:49       ` Johannes Thumshirn
2020-10-13 16:13     ` David Sterba
2020-10-01 18:36   ` [PATCH v8 05/41] btrfs: introduce max_zone_append_size Naohiro Aota
2020-10-01 18:36   ` [PATCH v8 06/41] btrfs: disallow space_cache in ZONED mode Naohiro Aota
2020-10-01 18:36   ` [PATCH v8 07/41] btrfs: disallow NODATACOW " Naohiro Aota
2020-10-13 15:39     ` David Sterba
2020-10-21  8:53       ` Johannes Thumshirn
2020-10-01 18:36   ` [PATCH v8 08/41] btrfs: disable fallocate " Naohiro Aota
2020-10-01 18:36   ` [PATCH v8 09/41] btrfs: disallow mixed-bg " Naohiro Aota
2020-10-01 18:36   ` [PATCH v8 10/41] btrfs: disallow inode_cache " Naohiro Aota
2020-10-13 15:41     ` David Sterba
2020-10-22  6:48       ` Naohiro Aota
2020-10-01 18:36   ` [PATCH v8 11/41] btrfs: implement log-structured superblock for " Naohiro Aota
2020-10-01 18:36   ` [PATCH v8 12/41] btrfs: implement zoned chunk allocator Naohiro Aota
2020-10-01 18:36   ` [PATCH v8 13/41] btrfs: verify device extent is aligned to zone Naohiro Aota
2020-10-01 18:36   ` [PATCH v8 14/41] btrfs: load zone's alloction offset Naohiro Aota
2020-10-01 18:36   ` [PATCH v8 15/41] btrfs: emulate write pointer for conventional zones Naohiro Aota
2020-10-01 18:36   ` [PATCH v8 16/41] btrfs: track unusable bytes for zones Naohiro Aota
2020-10-01 18:36   ` [PATCH v8 17/41] btrfs: do sequential extent allocation in ZONED mode Naohiro Aota
2020-10-01 18:36   ` [PATCH v8 18/41] btrfs: reset zones of unused block groups Naohiro Aota
2020-10-01 18:36   ` [PATCH v8 19/41] btrfs: redirty released extent buffers in ZONED mode Naohiro Aota
2020-10-01 18:36   ` [PATCH v8 20/41] btrfs: extract page adding function Naohiro Aota
2020-10-01 18:36   ` [PATCH v8 21/41] btrfs: use bio_add_zone_append_page for zoned btrfs Naohiro Aota
2020-10-01 18:36   ` [PATCH v8 22/41] btrfs: handle REQ_OP_ZONE_APPEND as writing Naohiro Aota
2020-10-01 18:36   ` [PATCH v8 23/41] btrfs: split ordered extent when bio is sent Naohiro Aota
2020-10-01 18:36   ` [PATCH v8 24/41] btrfs: extend btrfs_rmap_block for specifying a device Naohiro Aota
2020-10-01 18:36   ` [PATCH v8 25/41] btrfs: use ZONE_APPEND write for ZONED btrfs Naohiro Aota
2020-10-13 16:45     ` David Sterba
2020-10-01 18:36   ` [PATCH v8 26/41] btrfs: enable zone append writing for direct IO Naohiro Aota
2020-10-01 18:36   ` [PATCH v8 27/41] btrfs: introduce dedicated data write path for ZONED mode Naohiro Aota
2020-10-01 18:36   ` [PATCH v8 28/41] btrfs: serialize meta IOs on " Naohiro Aota
2020-10-01 18:36   ` [PATCH v8 29/41] btrfs: wait existing extents before truncating Naohiro Aota
2020-10-01 18:36   ` [PATCH v8 30/41] btrfs: avoid async metadata checksum on ZONED mode Naohiro Aota
2020-10-01 18:36   ` [PATCH v8 31/41] btrfs: mark block groups to copy for device-replace Naohiro Aota
2020-10-01 18:36   ` [PATCH v8 32/41] btrfs: implement cloning for ZONED device-replace Naohiro Aota
2020-10-01 18:36   ` [PATCH v8 33/41] btrfs: implement copying " Naohiro Aota
2020-10-01 18:36   ` [PATCH v8 34/41] btrfs: support dev-replace in ZONED mode Naohiro Aota
2020-10-01 18:36   ` [PATCH v8 35/41] btrfs: enable relocation " Naohiro Aota
2020-10-01 18:36   ` [PATCH v8 36/41] btrfs: relocate block group to repair IO failure in ZONED Naohiro Aota
2020-10-01 18:36   ` [PATCH v8 37/41] btrfs: split alloc_log_tree() Naohiro Aota
2020-10-01 18:36   ` [PATCH v8 38/41] btrfs: extend zoned allocator to use dedicated tree-log block group Naohiro Aota
2020-10-13 16:26     ` David Sterba
2020-10-15  7:21       ` Johannes Thumshirn
2020-10-01 18:36   ` [PATCH v8 39/41] btrfs: serialize log transaction on ZONED mode Naohiro Aota
2020-10-01 18:36   ` [PATCH v8 40/41] btrfs: reorder log node allocation Naohiro Aota
2020-10-01 18:36   ` [PATCH v8 41/41] btrfs: enable to mount ZONED incompat flag Naohiro Aota
2020-10-02 13:39   ` [PATCH v8 01/41] block: add bio_add_zone_append_page Martin K. Petersen
2020-10-05  1:46     ` Damien Le Moal [this message]
2020-10-05 13:43     ` Christoph Hellwig
2020-10-06  1:26       ` Martin K. Petersen
2020-10-06  5:12         ` Damien Le Moal
2020-10-09 15:40 ` [PATCH v8 00/41] btrfs: zoned block device support Josef Bacik
2020-10-12  9:17   ` Naohiro Aota

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