From: Andy Grover <agrover@redhat.com>
To: Hannes Reinecke <hare@suse.de>
Cc: "Nicholas A. Bellinger" <nab@linux-iscsi.org>,
target-devel@vger.kernel.org, linux-scsi@vger.kernel.org
Subject: Re: [PATCH 0/32] Refcounts and rbtrees to increase luns above 255
Date: Tue, 17 Dec 2013 09:10:32 -0800 [thread overview]
Message-ID: <52B08588.6080102@redhat.com> (raw)
In-Reply-To: <52B02D13.9000207@suse.de>
On 12/17/2013 02:53 AM, Hannes Reinecke wrote:
> But the LUN addressing improvements is interesting.
>
> What I found during development of the 64bit LUN patchset is
> that the target core stuff has a very rudimentary LUN handling:
> - 256 LUNs only
> - LUNs are kept in a static array
> - Identity mapping between LUN numbers and array indices.
>
> What I _really_ would like to have is to do away with the
> LUN array, and introduce a dynamic LUN mapping.
> This will allow us to easily implement different LUN enumeration
> methods (Think of hierarchical LUNs ...).
>
> Also the assumption that a static array is always faster for
> lookup than a linked list is wrong.
> A static array is faster if the entire array fits into the processor
> cache. If it doesn't we basically have an immediate
> cache miss _for every array access_.
> Then linked lists etc really are faster.
>
> So do not take things at face value; only real measurements
> count here.
Yeah, seems true. So do either of you have any tips for how best to do
measurements?
BTW I was looking a little more and am now inclined to think a radix
tree is more suitable than rbtree. It seems ideally suited for our case:
want to lookup by an index (i.e. LUN) that is usually a small integer,
very fast lookups, yet also can grow and still be space-efficient.
Regards -- Andy
next prev parent reply other threads:[~2013-12-17 17:10 UTC|newest]
Thread overview: 81+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-12-13 23:58 [PATCH 0/32] Refcounts and rbtrees to increase luns above 255 Andy Grover
2013-12-13 23:58 ` [PATCH 01/32] target: Remove unused ua_dev_list member in struct se_ua Andy Grover
2013-12-16 20:39 ` Nicholas A. Bellinger
2013-12-13 23:58 ` [PATCH 02/32] target: Don't keep looping in report_luns if too big Andy Grover
2013-12-16 20:41 ` Nicholas A. Bellinger
2013-12-13 23:58 ` [PATCH 03/32] target: Allocate more room for port default groups Andy Grover
2013-12-16 20:43 ` Nicholas A. Bellinger
2013-12-13 23:58 ` [PATCH 04/32] target: Fix sizeof in kmalloc for some default_groups arrays Andy Grover
2013-12-16 20:43 ` Nicholas A. Bellinger
2013-12-13 23:58 ` [PATCH 05/32] target: Rename some list heads used as nodes Andy Grover
2013-12-16 20:45 ` Nicholas A. Bellinger
2013-12-13 23:58 ` [PATCH 06/32] target: Convert lu_gp_ref_cnt to kref Andy Grover
2013-12-16 20:52 ` Nicholas A. Bellinger
2014-02-05 22:02 ` Andy Grover
2014-02-06 23:51 ` Nicholas A. Bellinger
2014-02-07 2:56 ` Andy Grover
2014-02-07 19:17 ` Nicholas A. Bellinger
2013-12-13 23:58 ` [PATCH 07/32] target: Convert struct alua_lu_gp_member " Andy Grover
2013-12-16 20:56 ` Nicholas A. Bellinger
2013-12-13 23:58 ` [PATCH 08/32] target: Convert tg_pt_gp_ref_cnt " Andy Grover
2013-12-16 21:00 ` Nicholas A. Bellinger
2013-12-13 23:58 ` [PATCH 09/32] target: convert tg_pt_gp_mem_ref_cnt " Andy Grover
2013-12-16 21:08 ` Nicholas A. Bellinger
2013-12-13 23:58 ` [PATCH 10/32] target: Change sep_tg_pt_ref_cnt to use kref Andy Grover
2013-12-16 21:11 ` Nicholas A. Bellinger
2013-12-13 23:58 ` [PATCH 11/32] target: Convert se_dev_entry to kref Andy Grover
2013-12-16 21:15 ` Nicholas A. Bellinger
2013-12-13 23:59 ` [PATCH 12/32] target: Convert t10_pr_registration " Andy Grover
2013-12-16 21:20 ` Nicholas A. Bellinger
2013-12-13 23:59 ` [PATCH 13/32] target: Move spinlock inside core_release_port Andy Grover
2013-12-16 21:21 ` Nicholas A. Bellinger
2013-12-13 23:59 ` [PATCH 14/32] target: Remove extra percpu_ref_init Andy Grover
2013-12-16 21:23 ` Nicholas A. Bellinger
2013-12-13 23:59 ` [PATCH 15/32] target: Refer to u32 luns as unpacked_lun Andy Grover
2013-12-16 21:25 ` Nicholas A. Bellinger
2013-12-13 23:59 ` [PATCH 16/32] target: Rename core_tpg_{pre,post}_addlun for clarity Andy Grover
2013-12-16 21:29 ` Nicholas A. Bellinger
2013-12-13 23:59 ` [PATCH 17/32] target: Don't use void* when passing dev in core_tpg_add_lun Andy Grover
2013-12-16 21:29 ` Nicholas A. Bellinger
2013-12-13 23:59 ` [PATCH 18/32] target: More core_dev_del cleanups Andy Grover
2013-12-16 21:35 ` Nicholas A. Bellinger
2013-12-13 23:59 ` [PATCH 19/32] target: Convert to rbtree for se_dev_entry in se_node_acl Andy Grover
2013-12-16 21:40 ` Nicholas A. Bellinger
2013-12-17 1:00 ` Andy Grover
2013-12-17 1:54 ` Nicholas A. Bellinger
2013-12-13 23:59 ` [PATCH 20/32] target: Convert to rbtree for se_lun list in se_portal_group Andy Grover
2013-12-16 21:42 ` Nicholas A. Bellinger
2013-12-13 23:59 ` [PATCH 21/32] target: Remove lun_link and device magic Andy Grover
2013-12-16 21:44 ` Nicholas A. Bellinger
2013-12-13 23:59 ` [PATCH 22/32] target: Convert percpu_ref to kref Andy Grover
2013-12-16 21:44 ` Nicholas A. Bellinger
2013-12-13 23:59 ` [PATCH 23/32] target: Add lun->lun_tpg pointer Andy Grover
2013-12-16 21:45 ` Nicholas A. Bellinger
2013-12-13 23:59 ` [PATCH 24/32] target: Remove tpg from core_dev_export/unexport params Andy Grover
2013-12-16 21:46 ` Nicholas A. Bellinger
2013-12-13 23:59 ` [PATCH 25/32] target: Call remove_lun instead of del_lun in fabric_port_unlink Andy Grover
2013-12-16 21:47 ` Nicholas A. Bellinger
2013-12-13 23:59 ` [PATCH 26/32] target: Convert tpg_pr_ref_count to kref Andy Grover
2013-12-16 21:50 ` Nicholas A. Bellinger
2013-12-13 23:59 ` [PATCH 27/32] target: Move call to remove_lun to the release function from drop_link Andy Grover
2013-12-16 21:51 ` Nicholas A. Bellinger
2013-12-13 23:59 ` [PATCH 28/32] target: Convert acl_pr_ref_count to kref Andy Grover
2013-12-16 21:58 ` Nicholas A. Bellinger
2013-12-13 23:59 ` [PATCH 29/32] target: Simplify params to core_tpg_del_initiator_node_acl Andy Grover
2013-12-16 22:00 ` Nicholas A. Bellinger
2013-12-13 23:59 ` [PATCH 30/32] target: Change nacl's session refcount to use existing refcount Andy Grover
2013-12-16 22:01 ` Nicholas A. Bellinger
2013-12-13 23:59 ` [PATCH 31/32] target: Don't release and re-acquire some spinlocks in loops Andy Grover
2013-12-16 22:01 ` Nicholas A. Bellinger
2013-12-13 23:59 ` [PATCH 32/32] target: Increase MAX_LUNS_PER_TPG to 16384 Andy Grover
2013-12-16 9:20 ` Hannes Reinecke
2013-12-16 9:24 ` Hannes Reinecke
2013-12-16 22:01 ` Nicholas A. Bellinger
2013-12-16 22:03 ` [PATCH 0/32] Refcounts and rbtrees to increase luns above 255 Nicholas A. Bellinger
2013-12-17 1:49 ` Andy Grover
2013-12-17 1:59 ` Nicholas A. Bellinger
2013-12-17 2:03 ` Andy Grover
2013-12-17 3:03 ` Nicholas A. Bellinger
2013-12-17 10:53 ` Hannes Reinecke
2013-12-17 17:10 ` Andy Grover [this message]
2013-12-17 21:25 ` Nicholas A. Bellinger
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