Re: [PATCH 0/3] implement readpages() for block device to optimize sequential read

[Andrew Morton <akpm@linux-foundation.org>]

On Sat, 16 Aug 2014 02:09:44 +0900 Akinobu Mita <akinobu.mita@gmail.com> wrote:

> 2014-08-15 7:04 GMT+09:00 Andrew Morton <akpm@linux-foundation.org>:
> > On Tue,  5 Aug 2014 23:38:31 +0900 Akinobu Mita <akinobu.mita@gmail.com> wrote:
> >
> >> This patchset implements readpages() operation for block device by
> >> using mpage_readpages() which can create multipage BIOs instead of
> >> BIOs for each page and reduce system CPU time consumption.
> >
> > Patchset is simple and straightforward enough.  But who the
> > heck cares about the performance of buffered reads from /dev/XXX?
> 
> I tend to consider the block device as a baseline when I measure the
> performance of the storage device.  So I was a bit surprised when I saw
> the performance of buffered reads from filesystem is better than the one
> from block device.  That is the reason about this patch for me.

OK.  The lack of readpages for blockdevs has been an outstanding oddity
for a decade or longer - I think it's just that nobody was motivated to
do it because the workload isn't important.

But the implementation looks pretty simple so why not clean it up.

I grabbed the patches.