Yes, you can raise max_open_files as high as you have memory to cover.
The plan for Riak 2.0 is to make these settings automatic and dynamic. Then
the cache_size will automatically decline as max_open_files increases to cover
your dataset. Of course, there will be limits to prevent memory going to swap
or OOM.
Matthew
On Jul 30, 2013, at 4:51 AM, Christian Rosnes <christian.ros...@gmail.com>
wrote:
>
>
> On Sun, Jul 28, 2013 at 10:08 PM, Matthew Von-Maszewski <matth...@basho.com>
> wrote:
>
> leveldb has two independent caches: file cache and data block cache. You
> have raised the data block cache from its default 8M to 256M per your earlier
> note. I would recommend the follow:
>
> {max_open_files, 50}, %% 50 * 4Mbytes allocation for file cache
> {cache_size, 104857600}, %% 100Mbytes for data block cache
>
> The max_open_files default is 20 (which is internally reduced by 10). You
> are likely thrashing file opens. The file cache is far more important to
> performance than the data block cache.
>
> Find the LOG file within one of your database "vnode" directories. Look for
> a line like this ' compacted to: files[ 0 9 25 14 2 0 0 ]'. You would like
> to be covering that total count of files (plus 10) with your max_open_files
> setting. Take the cache_size down to as low as 8Mbytes to achieve the
> coverage. Once you are down to 8Mbytes of cache_size, you should go no lower
> and give up on full max_open_files coverage.
>
> Summary: total memory per vnode in 1.4 is (max_open_files - 10) * 4Mbytes +
> cache_size;
>
>
> Thank you.
>
> In app.config I have now set this for the eleveldb section:
>
> {cache_size, 8388608} %% 8MB
> {max_open_files, 260}
>
> The 'max_open_files' was based on the highest sum of the 6 numbers I read
> in the 'compacted to ...' line. Is this the right way to set this parameter,
> or is it too high to have any significant benefit ?
>
> After the sysctl.conf and app.config changes I've inserted about
> 50 million json objects via http and not seen any errors. The performance for
> each 1-hour test has ranged from 1700 to 1850 insert req/s.
> The bucket used during testing now contains over 84 million json objects.
>
> Btw - when I now check the logs:
>
> [root@riak01 leveldb]# grep 'compacted' */LOG
> 2013/07/29-19:38:14.650538 7f96a1bdc700 compacted to: files[ 0 1 21 289 0 0 0
> ]
> 2013/07/29-19:34:58.838520 7f9692138700 compacted to: files[ 2 0 30 288 0 0 0
> ]
> 2013/07/29-19:38:02.037188 7f96c51b8700 compacted to: files[ 1 0 27 301 0 0 0
> ]
> 2013/07/29-19:38:12.214409 7f96c51b8700 compacted to: files[ 1 0 26 302 0 0 0
> ]
> 2013/07/29-19:37:06.503530 7f96a1bdc700 compacted to: files[ 1 1 22 284 0 0 0
> ]
> 2013/07/29-19:31:41.932370 7f96bffff700 compacted to: files[ 0 1 25 291 0 0 0
> ]
> 2013/07/29-19:32:18.097417 7f96bffff700 compacted to: files[ 0 1 24 292 0 0 0
> ]
> 2013/07/29-19:30:20.986832 7f968e538700 compacted to: files[ 2 1 24 278 0 0 0
> ]
> 2013/07/29-19:37:47.139039 7f96c51b8700 compacted to: files[ 3 0 20 300 0 0 0
> ]
> 2013/07/29-19:15:10.950633 7f968db37700 compacted to: files[ 0 2 33 263 0 0 0
> ]
> 2013/07/29-19:33:01.001246 7f968e538700 compacted to: files[ 1 1 30 280 0 0 0
> ]
> 2013/07/29-19:31:41.494208 7f96bffff700 compacted to: files[ 1 1 25 283 0 0 0
> ]
> 2013/07/29-19:31:57.008503 7f96bffff700 compacted to: files[ 1 1 24 284 0 0 0
> ]
> 2013/07/29-19:39:00.008635 7f96a1bdc700 compacted to: files[ 0 1 31 289 0 0 0
> ]
>
> Could there be a benefit to increase 'max_open_files' even further, say to:
> 340 ?
> (assuming there is enough memory)
>
> Christian
> @NorSoulx
>
>
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