From: Jeff Garzik <jgarzik@pobox.com>
To: Tejun Heo <htejun@gmail.com>
Cc: albertcc@tw.ibm.com, linux-ide@vger.kernel.org
Subject: Re: [PATCH 3/4] libata: add per-device max_sectors
Date: Sun, 12 Feb 2006 23:58:07 -0500 [thread overview]
Message-ID: <43F011DF.6020203@pobox.com> (raw)
In-Reply-To: <43EFD73D.4070207@gmail.com>
Tejun Heo wrote:
> Jeff Garzik wrote:
>
>>
>> applied 3-4, though note that the Axboe code mentioned in the comment
>> is now in the kernel, so lba48 can be fixed properly.
>>
>
> Care to tell me which commit it was? I don't really understand the
> comment.
max_sectors was artificially clipped by the driver due to a system
inadequacy: if it truly built commands of 65,536 sectors, then for a
full queue, I/O in flight would lock down way too much system memory.
Hence, 1024, 2048, 4096 is an arbitrary figure chosen to balance large
per-command data size (desireable) and pinned memory (minimize).
The solution was to separate max_sectors -- the maximum we should attach
to each command -- with max_hw_sectors, the absolute hardware limit.
The system will tune max_sectors up and down, within the max_hw_sectors
limit.
Search the kernel changelog for max_hw_sectors.
Jeff
next prev parent reply other threads:[~2006-02-13 4:58 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-02-12 14:32 [PATCHSET] libata: make some configurations per-dev Tejun Heo
2006-02-12 14:32 ` [PATCH 1/4] libata: make ata_dev_knobble() per-device Tejun Heo
2006-02-12 19:29 ` Jeff Garzik
2006-02-12 14:32 ` [PATCH 2/4] libata: move cdb_len for host to device Tejun Heo
2006-02-12 14:32 ` [PATCH 4/4] libata: kill sht->max_sectors Tejun Heo
2006-02-12 14:32 ` [PATCH 3/4] libata: add per-device max_sectors Tejun Heo
2006-02-12 19:37 ` Jeff Garzik
2006-02-13 0:47 ` Tejun Heo
2006-02-13 4:58 ` Jeff Garzik [this message]
2006-02-15 7:24 ` [PATCH] libata: increase LBA48 max sectors to 65535 Tejun Heo
2006-02-15 13:07 ` Jens Axboe
2006-02-15 15:04 ` Tejun Heo
2006-02-15 15:12 ` Jens Axboe
2006-02-15 15:30 ` Tejun Heo
2006-02-15 19:03 ` Mark Lord
2006-02-15 20:21 ` Jeff Garzik
2006-02-15 23:05 ` Mark Lord
2006-02-20 11:23 ` Jeff Garzik
2006-02-20 13:54 ` Mark Lord
2006-02-20 13:58 ` Jens Axboe
2006-02-16 7:42 ` Jens Axboe
2006-02-20 11:25 ` Jeff Garzik
2006-02-20 11:44 ` Jens Axboe
2006-02-20 21:59 ` Jeff Garzik
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