From: Thavatchai Makphaibulchoke <thavatchai.makpahibulchoke@hp.com>
Subject: Re: [PATCH 0/2] fs/ext4: increase parallelism in updating ext4 orphan
 list
Date: Thu, 03 Oct 2013 17:20:17 -0600
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Cc: T Makphaibulchoke <tmac@hp.com>, Theodore Ts'o <tytso@mit.edu>,
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To: Andreas Dilger <adilger@dilger.ca>
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On 10/03/2013 06:28 PM, Andreas Dilger wrote:
> 
> It would also be possible to have a completely contention-free orphan
> inode list by only generating the on-disk orphan linked list in a
> pre-commit callback hook from an efficient in-memory list.  That would
> allow the common "add to orphan list; do something; remove from list"
> operations within a single transaction to run with minimal contention,
> and only the few rare cases of operations that exceed the lifetime of
> a single transaction would need to modify the on-disk list.
> 
> For example, a per-cpu list would be quite efficient, or a hash table.
> Then, a jbd2 callback run before the transaction commits could modify
> the requisite inodes and superblock.  All of those inodes are already
> (by definition) part of the transaction, so it won't add new buffers
> of the transaction.
> 
> I'm not necessarily against the current patch, just thinking aloud about
> how it might be improved further.
> 
> Cheers, Andreas
> 

Thanks again for the suggestion.  I'll rework this patch first and look into this possibility next.

Thanks,
Mak.