From: Christoph Hellwig <hch@lst.de>
To: Benjamin Coddington <bcodding@redhat.com>
Cc: linux-nfs@vger.kernel.org, hch@lst.de
Subject: Re: blocklayoutdriver and page_cache_next_hole
Date: Wed, 27 Apr 2016 09:53:19 +0200 [thread overview]
Message-ID: <20160427075319.GC28726@lst.de> (raw)
In-Reply-To: <alpine.OSX.2.19.9992.1604261302250.92748@planck>
On Tue, Apr 26, 2016 at 01:27:02PM -0400, Benjamin Coddington wrote:
> I'm doing some benchmarking on SCSI layout, and I ran into a case where
> bonnie++ seemingly stopped making forward progress.
>
> bl_pg_init_write() wants to figure out how big the layout should be and uses
> page_cache_next_hole() pretty aggressively if the inode size isn't equal to
> the mapping. Problem is that page_cache_next_hole() is fairly stupid about
> just walking through the page_cache radix tree by index.
>
> The end result is that for fairly large files (>4G) my machine spends all
> its time in __radix_tree_lookup(), and I might as well just use regular NFS.
Haha. One option is to simply optimize page_cache_next_hole, as that
should be easy and the read-ahead could would benefit as well. Or make
NFS pass through the writeback size and stop hacking around upper layers
in the layout driver. Both seem like useful options.
prev parent reply other threads:[~2016-04-27 7:53 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-04-26 17:27 blocklayoutdriver and page_cache_next_hole Benjamin Coddington
2016-04-27 7:53 ` Christoph Hellwig [this message]
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