From: Josef Bacik <jbacik@fusionio.com>
To: Zach Brown <zab@zabbo.net>
Cc: "linux-btrfs@vger.kernel.org" <linux-btrfs@vger.kernel.org>
Subject: Re: [PATCH] Btrfs: flush delayed inodes if we're short on space
Date: Thu, 21 Jun 2012 16:08:28 -0400 [thread overview]
Message-ID: <4FE37F3C.2020102@fusionio.com> (raw)
In-Reply-To: <4FE376F3.5030609@zabbo.net>
On 06/21/2012 03:33 PM, Zach Brown wrote:
>
>> + case FLUSH_DELAYED_ITEMS_NR:
>> + case FLUSH_DELAYED_ITEMS:
>> + nr = (*state == FLUSH_DELAYED_ITEMS_NR) ? 10 : -1;
>
> This 10 seemed awfully magical so I read a bit more.
>
> It appears to be an attempt to pop back up into reserve_metadata_bytes()
> to see if the caller has been satisfied before continuing on to apply
> all the delayed items.
>
> The magic number seems awfully clumsy. It'll either do too much work or
> will blow through all the delayed items, depending on the load. Is it
> too hard to have btrfs_run_delayed_items() check for the callers
> reservation and return if there's a chance that it'll be satisfied?
>
> Am I missing something? Over-thinking a rare path as the initial steps
> will tend to free up space most of the time?
>
Ugh sorry I just dug this patch out from last week and forgot I had just
picked an arbitrary number to make sure it was working. You are
correct, what I _meant_ to do (and will do after I respond) was
calculate how much we wanted to flush and then divide that by how much
the delayed inodes reserve and then multiply it by 2 for good measure.
Does that sound more reasonable? Thanks,
Josef
next prev parent reply other threads:[~2012-06-21 20:08 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-06-21 18:54 [PATCH] Btrfs: flush delayed inodes if we're short on space Josef Bacik
2012-06-21 19:33 ` Zach Brown
2012-06-21 20:08 ` Josef Bacik [this message]
2012-06-21 21:10 ` Zach Brown
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