lists.openwall.net   lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  linux-hardening  linux-cve-announce  PHC 
Open Source and information security mailing list archives
 
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date:	Thu, 11 Sep 2014 10:13:57 -0400
From:	Theodore Ts'o <tytso@....edu>
To:	Jan Kara <jack@...e.cz>
Cc:	Yuanhan Liu <yuanhan.liu@...ux.intel.com>,
	linux-ext4@...r.kernel.org, Andi Kleen <ak@...ux.intel.com>
Subject: Re: [PATCH] jbd2: remove __jbd2_journal_clean_checkpoint_list to
 solve scalability issue

On Thu, Sep 11, 2014 at 03:51:47PM +0200, Jan Kara wrote:
> 
> I'm not yet convinced that just dropping
> __jbd2_journal_clean_checkpoint_list() is the right thing to do. Some
> periodic cleaning of checkpointed entries would seem reasonable so that we
> don't save all that work for the moment we run out of space in the journal.
> I'll think how to do that in a more efficient way...

I'm sure Jan is aware of this, but for those following along, when we
completely run out of space in the journal, and we have to do a formal
checkpoint operation --- at which point, all file system activity has
to grind to a halt, at which point *all* of the CPU cores will be dead
in the water, which is bad for scalability, not to mention really
annoying users whose terminals are stalled or whose web requests are
completely stuck until the checkpoint completes.   :-)

So being able to clean up the journal so we don't have to do a forced
checkpoint operation which requires waiting for I/O operations is
rather important from a performance and usability point of view....

Cheers,

						- Ted
--
To unsubscribe from this list: send the line "unsubscribe linux-ext4" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html

Powered by blists - more mailing lists