lkml.org 
[lkml]   [2008]   [Jan]   [8]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [vm] writing to UDF DVD+RW (/dev/sr0) while under memory pressure: box ==> doorstop
From
Date

On Tue, 2008-01-08 at 03:38 -0800, Andrew Morton wrote:
> On Tue, 08 Jan 2008 12:05:16 +0100 Mike Galbraith <efault@gmx.de> wrote:

> > Seeks on DVD drives are apparently far FAR more horrible that I ever
> > imagined, so writing to a filesystem on a DVD+RW in effect constitutes
> > the stupid thing I was worried about above. Make an image, populate it,
> > write it instead... sure to be a truckload faster, and due to the VM
> > connection, much safer too. Oh well.
> >
>
> Well. From your earlier trace it appeared that something was causing
> the filesystem to perform synchronous inode writes - sync_dirty_buffer() was
> called.
>
> This will cause many more seeks than would occur if we were doing full
> delayed writing, with obvious throughput implications.

Yes, with UDF, the IO was _incredibly_ slow. With ext2, it was better,
though still very bad. I tested with that other OS, and it gets ~same
throughput with UDF as I got with ext2 (ick).

UDF does udf_clear_inode() -> write_inode_now(inode, 1)

I suppose I could try write_inode_now(inode, 0). Might unstick the box.

-Mike



\
 
 \ /
  Last update: 2008-01-08 16:25    [W:0.032 / U:2.740 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site