linux-ext4 - Re: some large dir testing results

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Date:   Fri, 21 Apr 2017 18:11:12 +0300
From:   Alexey Lyashkov <alexey.lyashkov@...il.com>
To:     Andreas Dilger <adilger@...ger.ca>
Cc:     linux-ext4 <linux-ext4@...r.kernel.org>,
        Artem Blagodarenko <artem.blagodarenko@...il.com>
Subject: Re: some large dir testing results


> 21 апр. 2017 г., в 0:10, Andreas Dilger <adilger@...ger.ca> написал(а):
> 
>> 2) Some JBD problems when create thread have a wait a shadow BH from a committed transaction.
>> [root@...k03 ~]# cat /proc/100993/stack
>> [<ffffffffa06a072e>] sleep_on_shadow_bh+0xe/0x20 [jbd2]
>> [<ffffffffa06a1bad>] do_get_write_access+0x2dd/0x4e0 [jbd2]
>> [<ffffffffa06a1dd7>] jbd2_journal_get_write_access+0x27/0x40 [jbd2]
>> [<ffffffffa08c7cab>] __ldiskfs_journal_get_write_access+0x3b/0x80 [ldiskfs]
>> [<ffffffffa08ce817>] __ldiskfs_new_inode+0x447/0x1300 [ldiskfs]
>> [<ffffffffa08948c8>] ldiskfs_create+0xd8/0x190 [ldiskfs]
>> [<ffffffff811eb42d>] vfs_create+0xcd/0x130
>> [<ffffffff811f0960>] SyS_mknodat+0x1f0/0x220
>> [<ffffffff811f09ad>] SyS_mknod+0x1d/0x20
>> [<ffffffff81645549>] system_call_fastpath+0x16/0x1b
> 
> You might consider to use "createmany -l" to link entries (at least 65k
> at a time) to the same inode (this would need changes to createmany to
> create more than 65k files), so that you are exercising the directory
> code and not loading so many inodes into memory?
> 

I have run a hardlink test now (it don’t finished all loops but some initial results is exist).
Initial creation rate for HDD case is ~130k hardlink per second,
after ~ 83580000 entries it dropped to the 30k-40k hard links per second.

Alex.