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Date:	Thu, 27 Sep 2012 14:28:12 +0800
From:	Zhi Yong Wu <zwu.kernel@...il.com>
To:	Dave Chinner <david@...morbit.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 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?
>
> track_hot_inode_ranges(inode, offset, length, rw)
> {
>         if (inode->i_sb->s_flags & MS_HOT_TRACKING)
>                 hot_inode_freq_update(inode, offset, length, rw);
> }
>
>> diff --git a/mm/page-writeback.c b/mm/page-writeback.c
>> index 5ad5ce2..552c861 100644
>> --- a/mm/page-writeback.c
>> +++ b/mm/page-writeback.c
>> @@ -35,6 +35,7 @@
>>  #include <linux/buffer_head.h> /* __set_page_dirty_buffers */
>>  #include <linux/pagevec.h>
>>  #include <linux/timer.h>
>> +#include <linux/hot_tracking.h>
>>  #include <trace/events/writeback.h>
>>
>>  /*
>> @@ -1895,13 +1896,33 @@ EXPORT_SYMBOL(generic_writepages);
>>  int do_writepages(struct address_space *mapping, struct writeback_control *wbc)
>>  {
>>       int ret;
>> +     pgoff_t start = 0;
>> +     u64 prev_count = 0, count = 0;
>>
>>       if (wbc->nr_to_write <= 0)
>>               return 0;
>> +
>> +     /* Hot data tracking */
>> +     if (TRACK_THIS_INODE(mapping->host)
>> +             && wbc->range_cyclic) {
>> +             start = mapping->writeback_index << PAGE_CACHE_SHIFT;
>> +             prev_count = (u64)wbc->nr_to_write;
>> +     }
>
> Why only wbc->range_cyclic? This won't record things like
> synchronous writes or fsync-triggered writes, are are far more
> likely to be to hot ranges in a file...
sorry, i don't undersand what  wbc->range_cyclic means. OK, i will fix
it in next version.

>
> Cheers,
>
> Dave.
> --
> Dave Chinner
> david@...morbit.com



-- 
Regards,

Zhi Yong Wu
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