| Message ID | 20240410150313.2820364-5-yi.zhang@huaweicloud.com |
|---|---|
| State | Superseded |
| Headers | show |
| Series | ext4: use iomap for regular file's buffered IO path and enable large folio | expand |
On Wed, Apr 10, 2024 at 11:03:12PM +0800, Zhang Yi wrote: > From: Zhang Yi <yi.zhang@huawei.com> > > The data sync dirty check in ext4_inode_datasync_dirty() is expansive > since jbd2_transaction_committed() holds journal->j_state lock when > journal is enabled, it costs a lot in high-concurrency iomap buffered > read/write paths, but we never check IOMAP_F_DIRTY in these cases, so > let's check it only in swap file, dax and direct IO cases. Tested by > Unixbench on 100GB ramdisk: > > ./Run -c 128 -i 10 fstime fsbuffer fsdisk > > == without this patch == > 128 CPUs in system; running 128 parallel copies of tests > > File Copy 1024 bufsize 2000 maxblocks 6332521.0 KBps > File Copy 256 bufsize 500 maxblocks 1639726.0 KBps > File Copy 4096 bufsize 8000 maxblocks 24018572.0 KBps > > == with this patch == > 128 CPUs in system; running 128 parallel copies of tests > > File Copy 1024 bufsize 2000 maxblocks 49229257.0 KBps > File Copy 256 bufsize 500 maxblocks 24057510.0 KBps > File Copy 4096 bufsize 8000 maxblocks 75704437.0 KBps > > Signed-off-by: Zhang Yi <yi.zhang@huawei.com> > --- > fs/ext4/inode.c | 10 +++++++--- > 1 file changed, 7 insertions(+), 3 deletions(-) > > diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c > index 1cb219d347af..269503749ef5 100644 > --- a/fs/ext4/inode.c > +++ b/fs/ext4/inode.c > @@ -3281,9 +3281,13 @@ static void ext4_set_iomap(struct inode *inode, struct iomap *iomap, > * there is no other metadata changes being made or are pending. > */ > iomap->flags = 0; > - if (ext4_inode_datasync_dirty(inode) || > - offset + length > i_size_read(inode)) > - iomap->flags |= IOMAP_F_DIRTY; > + if ((flags & (IOMAP_DAX | IOMAP_REPORT)) || > + ((flags & (IOMAP_WRITE | IOMAP_DIRECT)) == > + (IOMAP_WRITE | IOMAP_DIRECT))) { > + if (offset + length > i_size_read(inode) || > + ext4_inode_datasync_dirty(inode)) > + iomap->flags |= IOMAP_F_DIRTY; > + } NACK. This just adds a nasty landmine that anyone working on the iomap infrastructure can step on. i.e. any time we add a new check for IOMAP_F_DIRTY in the generic infrastructure, ext4 is going to break because it won't set the IOMAP_F_DIRTY flag correctly. If checking an inode is dirty is expensive on ext4, then make it less expensive and everyone will benefit. /me goes and looks at jbd2_transaction_committed() Oh, it it's just a sequence number comparison, and it needs a lock because it has to dereference the running/committed transactions structures to get the current sequence numbers. Why not just store the commiting/running transaction tids in the journal_t, and then you can sample them without needing any locking and the whole ext4_inode_datasync_dirty() scalability problem goes away... -Dave.
On 2024/5/1 17:27, Dave Chinner wrote: > On Wed, Apr 10, 2024 at 11:03:12PM +0800, Zhang Yi wrote: >> From: Zhang Yi <yi.zhang@huawei.com> >> >> The data sync dirty check in ext4_inode_datasync_dirty() is expansive >> since jbd2_transaction_committed() holds journal->j_state lock when >> journal is enabled, it costs a lot in high-concurrency iomap buffered >> read/write paths, but we never check IOMAP_F_DIRTY in these cases, so >> let's check it only in swap file, dax and direct IO cases. Tested by >> Unixbench on 100GB ramdisk: >> >> ./Run -c 128 -i 10 fstime fsbuffer fsdisk >> >> == without this patch == >> 128 CPUs in system; running 128 parallel copies of tests >> >> File Copy 1024 bufsize 2000 maxblocks 6332521.0 KBps >> File Copy 256 bufsize 500 maxblocks 1639726.0 KBps >> File Copy 4096 bufsize 8000 maxblocks 24018572.0 KBps >> >> == with this patch == >> 128 CPUs in system; running 128 parallel copies of tests >> >> File Copy 1024 bufsize 2000 maxblocks 49229257.0 KBps >> File Copy 256 bufsize 500 maxblocks 24057510.0 KBps >> File Copy 4096 bufsize 8000 maxblocks 75704437.0 KBps >> >> Signed-off-by: Zhang Yi <yi.zhang@huawei.com> >> --- >> fs/ext4/inode.c | 10 +++++++--- >> 1 file changed, 7 insertions(+), 3 deletions(-) >> >> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c >> index 1cb219d347af..269503749ef5 100644 >> --- a/fs/ext4/inode.c >> +++ b/fs/ext4/inode.c >> @@ -3281,9 +3281,13 @@ static void ext4_set_iomap(struct inode *inode, struct iomap *iomap, >> * there is no other metadata changes being made or are pending. >> */ >> iomap->flags = 0; >> - if (ext4_inode_datasync_dirty(inode) || >> - offset + length > i_size_read(inode)) >> - iomap->flags |= IOMAP_F_DIRTY; >> + if ((flags & (IOMAP_DAX | IOMAP_REPORT)) || >> + ((flags & (IOMAP_WRITE | IOMAP_DIRECT)) == >> + (IOMAP_WRITE | IOMAP_DIRECT))) { >> + if (offset + length > i_size_read(inode) || >> + ext4_inode_datasync_dirty(inode)) >> + iomap->flags |= IOMAP_F_DIRTY; >> + } > > NACK. This just adds a nasty landmine that anyone working on the > iomap infrastructure can step on. i.e. any time we add a new check > for IOMAP_F_DIRTY in the generic infrastructure, ext4 is going to > break because it won't set the IOMAP_F_DIRTY flag correctly. > > If checking an inode is dirty is expensive on ext4, then make it > less expensive and everyone will benefit. > > /me goes and looks at jbd2_transaction_committed() > > Oh, it it's just a sequence number comparison, and it needs a lock > because it has to dereference the running/committed transactions > structures to get the current sequence numbers. Why not just store > the commiting/running transaction tids in the journal_t, and then > you can sample them without needing any locking and the whole > ext4_inode_datasync_dirty() scalability problem goes away... > Indeed, it could be useful, and it seems could also simplify many other jbd2 processes. Thanks, Yi.
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c index 1cb219d347af..269503749ef5 100644 --- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c @@ -3281,9 +3281,13 @@ static void ext4_set_iomap(struct inode *inode, struct iomap *iomap, * there is no other metadata changes being made or are pending. */ iomap->flags = 0; - if (ext4_inode_datasync_dirty(inode) || - offset + length > i_size_read(inode)) - iomap->flags |= IOMAP_F_DIRTY; + if ((flags & (IOMAP_DAX | IOMAP_REPORT)) || + ((flags & (IOMAP_WRITE | IOMAP_DIRECT)) == + (IOMAP_WRITE | IOMAP_DIRECT))) { + if (offset + length > i_size_read(inode) || + ext4_inode_datasync_dirty(inode)) + iomap->flags |= IOMAP_F_DIRTY; + } if (map->m_flags & EXT4_MAP_NEW) iomap->flags |= IOMAP_F_NEW;