Re: [PATCH 11/19] bcache: Subtract dirty sectors of thin flash from cache_sectors in calculating writeback rate

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On 2017/7/13 下午12:12, Eric Wheeler wrote:
> On Tue, 11 Jul 2017, tang.junhui@xxxxxxxxxx wrote:
> 
>>> Based on the above implementation, non-dirty space from flash only
>>> bcache device will mislead writeback rate calculation too. So I suggest
>>> to subtract all buckets size from all flash only bcache devices. Then it
>>> might be something like,
>>
>> what is non-dirty space from flash only bcache device?
>> Where is non-dirty space from flash only bcache device?
> 
> Hi Tang, Coly:
>    
> Waas there more discussion on this thread, or is the patch good to go?  
> 
> Please send your ack if you're happy with it so I can queue it up.

I discussed with Tang offline, this patch is correct. But the patch
commit log should be improved. Now I help to work on it, should be done
quite soon.

Coly

>>
>>
>> 发件人:         Coly Li <i@xxxxxxx>
>> 收件人:         Tang Junhui <tang.junhui@xxxxxxxxxx>,
>> 抄送:        bcache@xxxxxxxxxxxxxxxxxx, linux-block@xxxxxxxxxxxxxxx, linux-bcache@xxxxxxxxxxxxxxx,
>> hch@xxxxxxxxxxxxx, axboe@xxxxxxxxx, stable@xxxxxxxxxxxxxxx
>> 日期:         2017/07/11 02:11
>> 主题:        Re: [PATCH 11/19] bcache: Subtract dirty sectors of thin flash from cache_sectors in calculating
>> writeback rate
>> 发件人:        linux-bcache-owner@xxxxxxxxxxxxxxx
>>
>> _________________________________________________________________________________________________________________
>>
>>
>>
>> On 2017/7/1 上午4:43, bcache@xxxxxxxxxxxxxxxxxx wrote:
>>> From: Tang Junhui <tang.junhui@xxxxxxxxxx>
>>>
>>> Since dirty sectors of thin flash cannot be used to cache data for backend
>>> device, so we should subtract it in calculating writeback rate.
>>>
>>
>> I see you want to get ride of the noise of flash only cache device for
>> writeback rate calculation. It makes sense, because flash only cache
>> device won't have write back happen at all.
>>
>>
>>> Signed-off-by: Tang Junhui <tang.junhui@xxxxxxxxxx>
>>> Cc: stable@xxxxxxxxxxxxxxx
>>> ---
>>>  drivers/md/bcache/writeback.c |  2 +-
>>>  drivers/md/bcache/writeback.h | 19 +++++++++++++++++++
>>>  2 files changed, 20 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/md/bcache/writeback.c b/drivers/md/bcache/writeback.c
>>> index 4ac8b13..25289e4 100644
>>> --- a/drivers/md/bcache/writeback.c
>>> +++ b/drivers/md/bcache/writeback.c
>>> @@ -21,7 +21,7 @@
>>>  static void __update_writeback_rate(struct cached_dev *dc)
>>>  {
>>>                   struct cache_set *c = dc->disk.c;
>>> -                 uint64_t cache_sectors = c->nbuckets * c->sb.bucket_size;
>>> +                 uint64_t cache_sectors = c->nbuckets * c->sb.bucket_size -
>> bcache_flash_devs_sectors_dirty(c);
>>
>> See flash_dev_run(), the flash volume is created per struct
>> bcache_device of a cache set. That means, all data allocated for the
>> flash volume will be from a flash only bcache device. Regular dirty data
>> won't mixed allocating with flash volume dirty data on identical struct
>> bcache device.
>>
>> Based on the above implementation, non-dirty space from flash only
>> bcache device will mislead writeback rate calculation too. So I suggest
>> to subtract all buckets size from all flash only bcache devices. Then it
>> might be something like,
>>
>> uint64_t cache_sectors = c->nbuckets * c->sb.bucket_size -
>>                                                   bcache_flash_devs_nbuckets(c);
>>
>>
>>
>> Just FYI. Thanks.
>>
>> Coly
>>
>>>                   uint64_t cache_dirty_target =
>>>                                    div_u64(cache_sectors * dc->writeback_percent, 100);
>>>  
>>> diff --git a/drivers/md/bcache/writeback.h b/drivers/md/bcache/writeback.h
>>> index c2ab4b4..24ff589 100644
>>> --- a/drivers/md/bcache/writeback.h
>>> +++ b/drivers/md/bcache/writeback.h
>>> @@ -14,6 +14,25 @@ static inline uint64_t bcache_dev_sectors_dirty(struct bcache_device *d)
>>>                   return ret;
>>>  }
>>>  
>>> +static inline uint64_t  bcache_flash_devs_sectors_dirty(struct cache_set *c)
>>> +{
>>> +                 uint64_t i, ret = 0;
>>> +
>>> +                 mutex_lock(&bch_register_lock);
>>> +
>>> +                 for (i = 0; i < c->nr_uuids; i++) {
>>> +                                  struct bcache_device *d = c->devices[i];
>>> +
>>> +                                  if (!d || !UUID_FLASH_ONLY(&c->uuids[i]))
>>> +                                                   continue;
>>> +                    ret += bcache_dev_sectors_dirty(d);
>>> +                 }
>>> +
>>> +                 mutex_unlock(&bch_register_lock);
>>> +
>>> +                 return ret;
>>> +}
>>> +
>>>  static inline unsigned offset_to_stripe(struct bcache_device *d,
>>>                                                                                       uint64_t offset)
>>>  {
>>>
>> --
>> To unsubscribe from this list: send the line "unsubscribe linux-bcache" in
>> the body of a message to majordomo@xxxxxxxxxxxxxxx
>> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>>
>>
>>


-- 
Coly Li



[Index of Archives]     [Linux Kernel]     [Kernel Development Newbies]     [Linux USB Devel]     [Video for Linux]     [Linux Audio Users]     [Yosemite Hiking]     [Linux Kernel]     [Linux SCSI]