On Mon, Jun 19, 2017 at 05:03:16PM +0100, Al Viro wrote: > On Mon, Jun 19, 2017 at 09:01:36PM +0800, Sean Fu wrote: > > Make alloc_page_buffers support circular buffer list and initialise > > b_state field. > > Optimize the performance by removing the buffer list traversal to create > > circular buffer list. > > > - bh = head = alloc_page_buffers(page, blocksize, 1); > > + bh = head = alloc_page_buffers(page, blocksize, 1, 0, 0); > > Frankly, I don't like that change of calling conventions; it's very easy to > mess the order of arguments when using interfaces like that and it's hell > to find when trying to debug the resulting mess. > > Do you really get an observable change in performance? What loads are > triggering it? Sorry for my mistake. Infact, The time of writting a large file depends on saveral other factors, eg system workload. Yesterday, I tried to test the time of single calling create_empty_buffers by kretprobe and found that the performance difference is too small to measure it. before: [ 944.632027] create_empty_buffers returned 878736736 and took 2160 ns to execute [ 944.632286] create_empty_buffers returned 878962832 and took 451 ns to execute [ 944.632302] create_empty_buffers returned 878962016 and took 226 ns to execute [ 944.632728] create_empty_buffers returned 878962832 and took 235 ns to execute [ 944.633105] create_empty_buffers returned 878962832 and took 167 ns to execute [ 944.633421] create_empty_buffers returned 878962832 and took 160 ns to execute after: [39209.076519] create_empty_buffers returned 383804768 and took 1666 ns to execute [39209.077032] create_empty_buffers returned 383804768 and took 366 ns to execute [39209.077120] create_empty_buffers returned 558412336 and took 179 ns to execute [39209.077127] create_empty_buffers returned 558413152 and took 148 ns to execute [39209.077525] create_empty_buffers returned 558412336 and took 201 ns to execute [39209.078255] create_empty_buffers returned 814328768 and took 880 ns to execute [39209.078498] create_empty_buffers returned 558412336 and took 564 ns to execute [39209.078737] create_empty_buffers returned 558413152 and took 196 ns to execute This patch also complicates code. Please ignore it. Thanks all of you.
