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Date: Mon, 22 Feb 2010 22:23:17 -0500 From: tytso@....edu To: Dave Chinner <david@...morbit.com> Cc: Jan Kara <jack@...e.cz>, Linus Torvalds <torvalds@...ux-foundation.org>, Jens Axboe <jens.axboe@...cle.com>, Linux Kernel <linux-kernel@...r.kernel.org>, jengelh@...ozas.de, stable@...nel.org, gregkh@...e.de Subject: Re: [PATCH] writeback: Fix broken sync writeback On Tue, Feb 23, 2010 at 01:53:50PM +1100, Dave Chinner wrote: > > Ignoring nr_to_write completely can lead to issues like we used to > have with XFS - it would write an entire extent (8GB) at a time and > starve all other writeback. Those starvation problems - which were > very obvious on NFS servers - went away when we trimmed back the > amount to write in a single pass to saner amounts... How do you determine what a "sane amount" is? Is it something that is determined dynamically, or is it a hard-coded or manually tuned value? > As to a generic solution, why do you think I've been advocating > separate per-sb data sync and inode writeback methods that separate > data writeback from inode writeback for so long? ;) Heh. > > This is done to avoid a lock inversion, and so this is an > > ext4-specific thing (at least I don't think XFS's delayed allocation > > has this misfeature). > > Not that I know of, but then again I don't know what inversion ext4 > is trying to avoid. Can you describe the inversion, Ted? The locking order is journal_start_handle (starting a micro transaction in jbd) -> lock_page. A more detailed description of why this locking order is non-trivial for us to fix in ext4 can be found in the description of commit f0e6c985. Regards, - Ted -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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