(2012/12/26 2:22), Sha Zhengju wrote: > From: Sha Zhengju <handai.szj@xxxxxxxxxx> > > Commit a8e7d49a(Fix race in create_empty_buffers() vs __set_page_dirty_buffers()) > extracts TestSetPageDirty from __set_page_dirty and is far away from > account_page_dirtied. But it's better to make the two operations in one single > function to keep modular. So in order to avoid the potential race mentioned in > commit a8e7d49a, we can hold private_lock until __set_page_dirty completes. > There's no deadlock between ->private_lock and ->tree_lock after confirmation. > It's a prepare patch for following memcg dirty page accounting patches. > > > Here is some test numbers that before/after this patch: > Test steps(Mem-4g, ext4): > drop_cache; sync > fio (ioengine=sync/write/buffered/bs=4k/size=1g/numjobs=2/group_reporting/thread) > > We test it for 10 times and get the average numbers: > Before: > write: io=2048.0MB, bw=254117KB/s, iops=63528.9 , runt= 8279msec > lat (usec): min=1 , max=742361 , avg=30.918, stdev=1601.02 > After: > write: io=2048.0MB, bw=254044KB/s, iops=63510.3 , runt= 8274.4msec > lat (usec): min=1 , max=856333 , avg=31.043, stdev=1769.32 > > Note that the impact is little(<1%). > > > Signed-off-by: Sha Zhengju <handai.szj@xxxxxxxxxx> > Reviewed-by: Michal Hocko <mhocko@xxxxxxx> Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> Hmm,..this change should be double-checked by vfs, I/O guys... increasing hold time of mapping->private_lock doesn't affect performance ? -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>