linux-kernel - Re: [RFC v2 06/10] vfs: enable hot data tracking

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Message-ID: <20120927065953.GQ15236@dastard>
Date:	Thu, 27 Sep 2012 16:59:53 +1000
From:	Dave Chinner <david@...morbit.com>
To:	Zhi Yong Wu <zwu.kernel@...il.com>
Cc:	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-btrfs@...r.kernel.org, linux-ext4@...r.kernel.org,
	linuxram@...ux.vnet.ibm.com, viro@...iv.linux.org.uk,
	cmm@...ibm.com, tytso@....edu, marco.stornelli@...il.com,
	stroetmann@...olinux.com, diegocg@...il.com, chris@...muel.org,
	Zhi Yong Wu <wuzhy@...ux.vnet.ibm.com>
Subject: Re: [RFC v2 06/10] vfs: enable hot data tracking

On Thu, Sep 27, 2012 at 02:28:12PM +0800, Zhi Yong Wu wrote:
> On Thu, Sep 27, 2012 at 11:54 AM, Dave Chinner <david@...morbit.com> wrote:
> > On Sun, Sep 23, 2012 at 08:56:31PM +0800, zwu.kernel@...il.com wrote:
> >> From: Zhi Yong Wu <wuzhy@...ux.vnet.ibm.com>
> >>
> >>   Miscellaneous features that implement hot data tracking
> >> and generally make the hot data functions a bit more friendly.
> >>
> >> Signed-off-by: Zhi Yong Wu <wuzhy@...ux.vnet.ibm.com>
> >> ---
> >>  fs/direct-io.c               |   10 ++++++++++
> >>  include/linux/hot_tracking.h |   11 +++++++++++
> >>  mm/filemap.c                 |    8 ++++++++
> >>  mm/page-writeback.c          |   21 +++++++++++++++++++++
> >>  mm/readahead.c               |    9 +++++++++
> >>  5 files changed, 59 insertions(+), 0 deletions(-)
> >>
> >> diff --git a/fs/direct-io.c b/fs/direct-io.c
> >> index f86c720..3773f44 100644
> >> --- a/fs/direct-io.c
> >> +++ b/fs/direct-io.c
> >> @@ -37,6 +37,7 @@
> >>  #include <linux/uio.h>
> >>  #include <linux/atomic.h>
> >>  #include <linux/prefetch.h>
> >> +#include "hot_tracking.h"
> >>
> >>  /*
> >>   * How many user pages to map in one call to get_user_pages().  This determines
> >> @@ -1297,6 +1298,15 @@ __blockdev_direct_IO(int rw, struct kiocb *iocb, struct inode *inode,
> >>       prefetch(bdev->bd_queue);
> >>       prefetch((char *)bdev->bd_queue + SMP_CACHE_BYTES);
> >>
> >> +     /* Hot data tracking */
> >> +     if (TRACK_THIS_INODE(iocb->ki_filp->f_mapping->host)
> >> +                     && iov_length(iov, nr_segs) > 0) {
> >> +             hot_rb_update_freqs(iocb->ki_filp->f_mapping->host,
> >> +                             (u64)offset,
> >> +                             (u64)iov_length(iov, nr_segs),
> >> +                             rw & WRITE);
> >> +     }
> >
> > That's a bit messy. I'd prefer a static inline function that hides
> > all this. e.g.
> Do you think of moving the condition into hot_inode_udate_freqs(), not
> adding another new function?

Moving it into hot_inode_udate_freqs() will add a function call
overhead even when tracking is not enabled. a static inline function
will just result in no extra overhead other than the if
statement....

Cheers,

Dave.
-- 
Dave Chinner
david@...morbit.com
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