Hi Ted, After applying Ritesh's patches, from my test result, there is no obvious performance difference between default mount options and with dioread_lock (delalloc or nodelalloc). I'm not sure if dioread_nolock was used for other purpose in the scenario reported by Bo Liu. Maybe Xiaoguang could give some inputs. Thanks, Joseph On 19/12/26 23:31, Theodore Y. Ts'o wrote: > With inclusion of Ritesh's inode lock scalability patches[1], the > traditional performance reasons for dioread_nolock --- namely, > removing the need to take an exclusive lock for Direct I/O read > operations --- has been removed. > > [1] https://lore.kernel.org/r/20191212055557.11151-1-riteshh@xxxxxxxxxxxxx > > So... is it time to remove the code which supports dioread_nolock? > Doing so would simplify the code base, and reduce the test matrix. > This would also make it easier to restructure the write path when > allocating blocks so that the extent tree is updated after writing out > the data blocks, by clearing away the underbrush of dioread nolock > first. > > If we do this, we'd leave the dioread_nolock mount option for > backwards compatibility, but it would be a no-op and not actually do > anything. > > Any objections before I look into ripping out dioread_nolock? > > The one possible concern that I considered was for Alibaba, which was > doing something interesting with dioread_nolock plus nodelalloc. But > looking at Liu Bo's explanation[2], I believe that their workload > would be satisfied simply by using the standard ext4 mount options > (that is, the default mode has the performance benefits when doing > parallel DIO reads, and so the need for nodelalloc to mitigate the > tail latency concerns which Alibaba was seeing in their workload would > not be needed). Could Liu or someone from Alibaba confirm, perhaps > with some benchmarks using their workload? > > [2] https://lore.kernel.org/linux-ext4/20181121013035.ab4xp7evjyschecy@US-160370MP2.local/ > > - Ted >
