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From: Douglas Gilbert <dgilbert@interlog.com>
To: SCSI development list <linux-scsi@vger.kernel.org>,
	Hannes Reinecke <hare@suse.de>
Subject: RFC: split struct scsi_device in two
Date: Thu, 4 Jun 2020 12:08:38 -0400	[thread overview]
Message-ID: <5bcc1fee-e221-e54a-d754-d04a2e6fda33@interlog.com> (raw)

The scsi_device structure seems to be carrying around a lot of baggage.
Assuming the object needs to be present on the SCSI fast path then
making it smaller will help in fitting one or several of them in cache
lines.

Now the effort to use xarrays is helping, but only in the order 32 bytes
at the moment. Currently we have pointers to the standard inquiry response
and several VPD pages with more VPD pages to come, I suspect.

So what about having a secondary scsi_device object (with a more
descriptive name) for all those parts of the currect scsi_device
object that aren't needed for the fast path? The secondary object
could be created in scsi_alloc_sdev() and pointed to by the
primary object (and vice versa). Then adding more context info
(e.g. more VPD pages) will not burden the fast path.

sizeof(struct scsi_device)=1976 bytes!

Comments?

Doug Gilbert


             reply	other threads:[~2020-06-04 16:08 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-04 16:08 Douglas Gilbert [this message]
2020-06-04 16:15 ` RFC: split struct scsi_device in two Hannes Reinecke

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