Re: scsi vs ide performance on fsync's

Jeremy Hansen
2001-03-02T19:27:37Z

On Fri, 2 Mar 2001, Steve Lord wrote:

> >
> >
> > On Friday, March 02, 2001 12:39:01 PM -0600 Steve Lord <lord@sgi.com> wrote:
> >
> > [ file_fsync syncs all dirty buffers on the FS ]
> > >
> > > So it looks like fsync is going to cost more for bigger devices. Given the
> > > O_SYNC changes Stephen Tweedie did, couldnt fsync look more like this:
> > >
> > > down(&inode->i_sem);
> > > filemap_fdatasync(ip->i_mapping);
> > > fsync_inode_buffers(ip);
> > > filemap_fdatawait(ip->i_mapping);
> > > up(&inode->i_sem);
> > >
> >
> > reiserfs might need to trigger a commit on fsync, so the fs specific fsync
> > op needs to be called. But, you should not need to call file_fsync in the
> > XFS fsync call (check out ext2's)
>
>
> Right, this was just a generic example, the fsync_inode_buffers would be in
> the filesystem specific fsync callout - this was more of a logical
> example of what ext2 could do. XFS does completely different stuff in there
> anyway.
>
> >
> > For why ide is beating scsi in this benchmark...make sure tagged queueing
> > is on (or increase the queue length?). For the xlog.c test posted, I would
> > expect scsi to get faster than ide as the size of the write increases.
>
> I think the issue is the call being used now is going to get slower the
> larger the device is, just from the point of view of how many buffers it
> has to scan.

Well, I tried making the device smaller, creating just a 9gig partition on
the raid array and this made no different in the xlog results.

-jeremy

> >
> > -chris
>
> Steve
>
>
>

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