Shaan Nobee 411f4a018d Speed up WB_SYNC_NONE when a WB_SYNC_ALL occurs simultaneously ... Page writebacks with WB_SYNC_NONE can take several seconds to complete since they wait for the transaction group to close before being committed. This is usually not a problem since the caller does not need to wait. However, if we're simultaneously doing a writeback with WB_SYNC_ALL (e.g via msync), the latter can block for several seconds (up to zfs_txg_timeout) due to the active WB_SYNC_NONE writeback since it needs to wait for the transaction to complete and the PG_writeback bit to be cleared. This commit deals with 2 cases: - No page writeback is active. A WB_SYNC_ALL page writeback starts and even completes. But when it's about to check if the PG_writeback bit has been cleared, another writeback with WB_SYNC_NONE starts. The sync page writeback ends up waiting for the non-sync page writeback to complete. - A page writeback with WB_SYNC_NONE is already active when a WB_SYNC_ALL writeback starts. The WB_SYNC_ALL writeback ends up waiting for the WB_SYNC_NONE writeback. The fix works by carefully keeping track of active sync/non-sync writebacks and committing when beneficial. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Shaan Nobee <sniper111@gmail.com> Closes #12662 Closes #12790		2022-05-03 13:23:26 -07:00
..
sys	Speed up WB_SYNC_NONE when a WB_SYNC_ALL occurs simultaneously	2022-05-03 13:23:26 -07:00
Makefile.am	OpenZFS restructuring - move platform specific headers	2019-09-05 09:34:54 -07:00