Re: [PATCH v3 00/17] Replace btrfs_workers with kernel workqueue based btrfs_workqueue_struct

[Chris Mason <chris.mason@fusionio.com>]

Quoting Qu Wenruo (2013-11-07 00:51:50)
> Add a new btrfs_workqueue_struct which use kernel workqueue to implement
> most of the original btrfs_workers, to replace btrfs_workers.
> 
> With this patchset, redundant workqueue codes are replaced with kernel
> workqueue infrastructure, which not only reduces the code size but also the
> effort to maintain it.
> 
> More performace tests are ongoing, the result from sysbench shows minor
> improvement on the following server:
> CPU: two-way Xeon X5660
> RAM: 4G 
> HDD: SAS HDD, 150G total, 40G partition for btrfs test
> 
> Test result:
> Mode|Num_threads|block size|extra flags|performance change vs 3.11 kernel
> rndrd   1       4K      none            +1.22%
> rndrd   1       32K     none            +1.00%
> rndrd   8       32K     sync            +1.35%
> seqrd   8       4K      direct          +5.56%
> seqwr   8       4K      none            -1.26%
> seqwr   8       32K     sync            +1.20%
> 
> Changes below 1% are not mentioned.
> Overall the patchset doesn't change the performance on HDD.
> 
> Since more tests are needed, more test result are welcomed.

Thanks for working on this, it's really good to move toward a single set
of workqueues in the kernel.

Have you benchmarked with compression on?  Especially on modern
hardware, the crcs don't exercise the workqueues very much.

-chris