From: Hannes Reinecke <hare@suse.de>
To: Shaun Tancheff <shaun@tancheff.com>,
linux-block@vger.kernel.org, linux-scsi@vger.kernel.org,
linux-kernel@vger.kernel.org
Cc: Jens Axboe <axboe@kernel.dk>, Jens Axboe <axboe@fb.com>,
Christoph Hellwig <hch@lst.de>,
"James E . J . Bottomley" <jejb@linux.vnet.ibm.com>,
"Martin K . Petersen" <martin.petersen@oracle.com>,
Damien Le Moal <damien.lemoal@hgst.com>,
Dan Williams <dan.j.williams@intel.com>,
Sagi Grimberg <sagig@mellanox.com>,
Mike Christie <mchristi@redhat.com>,
Ming Lei <ming.lei@canonical.com>,
Josh Bingaman <josh.bingaman@seagate.com>,
Shaun Tancheff <shaun.tancheff@seagate.com>
Subject: Re: [PATCH 2/2] Migrate zone cache from RB-Tree to arrays of descriptors
Date: Mon, 22 Aug 2016 09:11:58 +0200 [thread overview]
Message-ID: <ad5c983d-ae7c-bd5b-edef-b56552c3038b@suse.de> (raw)
In-Reply-To: <20160822043402.8855-3-shaun@tancheff.com>
On 08/22/2016 06:34 AM, Shaun Tancheff wrote:
> Currently the RB-Tree zone cache is fast and flexible. It does
> use a rather largish amount of ram. This model reduces the ram
> required from 120 bytes per zone to 16 bytes per zone with a
> moderate transformation of the blk_zone_lookup() api.
>
> This model is predicated on the belief that most variations
> on zoned media will follow a pattern of using collections of same
> sized zones on a single device. Similar to the pattern of erase
> blocks on flash devices being progressivly larger 16K, 64K, ...
>
> The goal is to be able to build a descriptor which is both memory
> efficient, performant, and flexible.
>
> Signed-off-by: Shaun Tancheff <shaun.tancheff@seagate.com>
> ---
> block/blk-core.c | 2 +-
> block/blk-sysfs.c | 31 +-
> block/blk-zoned.c | 103 +++--
> drivers/scsi/sd.c | 5 +-
> drivers/scsi/sd.h | 4 +-
> drivers/scsi/sd_zbc.c | 1025 +++++++++++++++++++++++++++---------------------
> include/linux/blkdev.h | 82 +++-
> 7 files changed, 716 insertions(+), 536 deletions(-)
>
Have you measure the performance impact here?
The main idea behind using an RB-tree is that each single element will
fit in the CPU cache; using an array will prevent that.
So we will increase the number of cache flushes, and most likely a
performance penalty, too.
Hence I'd rather like to see a performance measurement here before going
down that road.
Cheers,
Hannes
--
Dr. Hannes Reinecke Teamlead Storage & Networking
hare@suse.de +49 911 74053 688
SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: F. Imendörffer, J. Smithard, J. Guild, D. Upmanyu, G. Norton
HRB 21284 (AG Nürnberg)
next prev parent reply other threads:[~2016-08-22 7:12 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-08-22 4:34 [PATCH 0/2] Change zone cache format to use less memory Shaun Tancheff
2016-08-22 4:34 ` [PATCH 1/2] Move ZBC core setup to sd_zbc Shaun Tancheff
2016-08-22 4:34 ` [PATCH 2/2] Migrate zone cache from RB-Tree to arrays of descriptors Shaun Tancheff
2016-08-22 5:25 ` Shaun Tancheff
2016-08-22 7:11 ` Hannes Reinecke [this message]
2016-08-22 15:43 ` Shaun Tancheff
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