[<prev] [next>] [<thread-prev] [day] [month] [year] [list]
Date: Thu, 9 Sep 2010 13:11:07 +0200 (CEST)
From: Lukas Czerner <lczerner@...hat.com>
To: Andreas Dilger <adilger@...ger.ca>
cc: Lukas Czerner <lczerner@...hat.com>, linux-ext4@...r.kernel.org,
rwheeler@...hat.com, sandeen@...hat.com, tytso@....edu
Subject: Re: [PATCH 1/5] Add helper function for blkdev_issue_zeroout
On Wed, 8 Sep 2010, Andreas Dilger wrote:
> On 2010-09-08, at 10:59, Lukas Czerner wrote:
> > +static inline int sb_issue_zeroout(struct super_block *sb,
> > + sector_t block, sector_t nr_blocks)
> > +{
> > + block <<= (sb->s_blocksize_bits - 9);
> > + nr_blocks <<= (sb->s_blocksize_bits - 9);
> > + return blkdev_issue_zeroout(sb->s_bdev, block, nr_blocks, GFP_KERNEL,
> > + BLKDEV_IFL_WAIT | BLKDEV_IFL_BARRIER);
> > +}
>
> While I can understand that we might need a barrier for this (to avoid
> it being reordered with later writes that are using these blocks), I'm
> not sure it needs to wait for previous IO to complete.
We are waiting for submitted bios to finish. Especially in my patch it
is needed, because I need to know how long it takes to get this IO on
disk do determine next schedule time, depending on the IO load. I am not
sure about this, but when it would not wait it will complete fairly
quickly and my "IO throttling" code would be useless.
And if I am wrong, and you are really convinced that it should not wait,
what about sb_issue_discard(), it is also waiting for completion, is it
ok?
Regards.
-Lukas
>
> Cheers, Andreas
>
--
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