| Message ID | 20211125070530.79602-5-jefflexu@linux.alibaba.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | fuse,virtiofs: support per-file DAX | expand |
On Thu, Nov 25, 2021 at 03:05:27PM +0800, Jeffle Xu wrote: > DAX may be limited in some specific situation. When the number of usable > DAX windows is under watermark, the recalim routine will be triggered to > reclaim some DAX windows. It may have a negative impact on the > performance, since some processes may need to wait for DAX windows to be > recalimed and reused then. To mitigate the performance degradation, the > overall DAX window need to be expanded larger. > > However, simply expanding the DAX window may not be a good deal in some > scenario. To maintain one DAX window chunk (i.e., 2MB in size), 32KB > (512 * 64 bytes) memory footprint will be consumed for page descriptors > inside guest, which is greater than the memory footprint if it uses > guest page cache when DAX disabled. Thus it'd better disable DAX for > those files smaller than 32KB, to reduce the demand for DAX window and > thus avoid the unworthy memory overhead. > > Per inode DAX feature is introduced to address this issue, by offering a > finer grained control for dax to users, trying to achieve a balance > between performance and memory overhead. > > The FUSE_ATTR_DAX flag in FUSE_LOOKUP reply is used to indicate whether > DAX should be enabled or not for corresponding file. Currently the state > whether DAX is enabled or not for the file is initialized only when > inode is instantiated. > > Signed-off-by: Jeffle Xu <jefflexu@linux.alibaba.com> Reviwed-by: Vivek Goyal <vgoyal@redhat.com> Vivek > --- > fs/fuse/dax.c | 12 ++++++++---- > fs/fuse/file.c | 4 ++-- > fs/fuse/fuse_i.h | 4 ++-- > fs/fuse/inode.c | 2 +- > 4 files changed, 13 insertions(+), 9 deletions(-) > > diff --git a/fs/fuse/dax.c b/fs/fuse/dax.c > index b9a031a82934..1550c3624414 100644 > --- a/fs/fuse/dax.c > +++ b/fs/fuse/dax.c > @@ -1332,7 +1332,7 @@ static const struct address_space_operations fuse_dax_file_aops = { > .invalidatepage = noop_invalidatepage, > }; > > -static bool fuse_should_enable_dax(struct inode *inode) > +static bool fuse_should_enable_dax(struct inode *inode, unsigned int flags) > { > struct fuse_conn *fc = get_fuse_conn(inode); > enum fuse_dax_mode dax_mode = fc->dax_mode; > @@ -1347,12 +1347,16 @@ static bool fuse_should_enable_dax(struct inode *inode) > if (!fc->dax) > return false; > > - return true; > + if (dax_mode == FUSE_DAX_ALWAYS) > + return true; > + > + /* dax_mode is FUSE_DAX_INODE* */ > + return flags & FUSE_ATTR_DAX; > } > > -void fuse_dax_inode_init(struct inode *inode) > +void fuse_dax_inode_init(struct inode *inode, unsigned int flags) > { > - if (!fuse_should_enable_dax(inode)) > + if (!fuse_should_enable_dax(inode, flags)) > return; > > inode->i_flags |= S_DAX; > diff --git a/fs/fuse/file.c b/fs/fuse/file.c > index 9d6c5f6361f7..90067584e103 100644 > --- a/fs/fuse/file.c > +++ b/fs/fuse/file.c > @@ -3169,7 +3169,7 @@ static const struct address_space_operations fuse_file_aops = { > .write_end = fuse_write_end, > }; > > -void fuse_init_file_inode(struct inode *inode) > +void fuse_init_file_inode(struct inode *inode, unsigned int flags) > { > struct fuse_inode *fi = get_fuse_inode(inode); > > @@ -3183,5 +3183,5 @@ void fuse_init_file_inode(struct inode *inode) > fi->writepages = RB_ROOT; > > if (IS_ENABLED(CONFIG_FUSE_DAX)) > - fuse_dax_inode_init(inode); > + fuse_dax_inode_init(inode, flags); > } > diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h > index 19ded93cfc49..f03ea7cb74b0 100644 > --- a/fs/fuse/fuse_i.h > +++ b/fs/fuse/fuse_i.h > @@ -1022,7 +1022,7 @@ int fuse_notify_poll_wakeup(struct fuse_conn *fc, > /** > * Initialize file operations on a regular file > */ > -void fuse_init_file_inode(struct inode *inode); > +void fuse_init_file_inode(struct inode *inode, unsigned int flags); > > /** > * Initialize inode operations on regular files and special files > @@ -1288,7 +1288,7 @@ int fuse_dax_conn_alloc(struct fuse_conn *fc, enum fuse_dax_mode mode, > struct dax_device *dax_dev); > void fuse_dax_conn_free(struct fuse_conn *fc); > bool fuse_dax_inode_alloc(struct super_block *sb, struct fuse_inode *fi); > -void fuse_dax_inode_init(struct inode *inode); > +void fuse_dax_inode_init(struct inode *inode, unsigned int flags); > void fuse_dax_inode_cleanup(struct inode *inode); > bool fuse_dax_check_alignment(struct fuse_conn *fc, unsigned int map_alignment); > void fuse_dax_cancel_work(struct fuse_conn *fc); > diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c > index 4a41e6a73f3f..0669e41a9645 100644 > --- a/fs/fuse/inode.c > +++ b/fs/fuse/inode.c > @@ -313,7 +313,7 @@ static void fuse_init_inode(struct inode *inode, struct fuse_attr *attr) > inode->i_ctime.tv_nsec = attr->ctimensec; > if (S_ISREG(inode->i_mode)) { > fuse_init_common(inode); > - fuse_init_file_inode(inode); > + fuse_init_file_inode(inode, attr->flags); > } else if (S_ISDIR(inode->i_mode)) > fuse_init_dir(inode); > else if (S_ISLNK(inode->i_mode)) > -- > 2.27.0 >
diff --git a/fs/fuse/dax.c b/fs/fuse/dax.c index b9a031a82934..1550c3624414 100644 --- a/fs/fuse/dax.c +++ b/fs/fuse/dax.c @@ -1332,7 +1332,7 @@ static const struct address_space_operations fuse_dax_file_aops = { .invalidatepage = noop_invalidatepage, }; -static bool fuse_should_enable_dax(struct inode *inode) +static bool fuse_should_enable_dax(struct inode *inode, unsigned int flags) { struct fuse_conn *fc = get_fuse_conn(inode); enum fuse_dax_mode dax_mode = fc->dax_mode; @@ -1347,12 +1347,16 @@ static bool fuse_should_enable_dax(struct inode *inode) if (!fc->dax) return false; - return true; + if (dax_mode == FUSE_DAX_ALWAYS) + return true; + + /* dax_mode is FUSE_DAX_INODE* */ + return flags & FUSE_ATTR_DAX; } -void fuse_dax_inode_init(struct inode *inode) +void fuse_dax_inode_init(struct inode *inode, unsigned int flags) { - if (!fuse_should_enable_dax(inode)) + if (!fuse_should_enable_dax(inode, flags)) return; inode->i_flags |= S_DAX; diff --git a/fs/fuse/file.c b/fs/fuse/file.c index 9d6c5f6361f7..90067584e103 100644 --- a/fs/fuse/file.c +++ b/fs/fuse/file.c @@ -3169,7 +3169,7 @@ static const struct address_space_operations fuse_file_aops = { .write_end = fuse_write_end, }; -void fuse_init_file_inode(struct inode *inode) +void fuse_init_file_inode(struct inode *inode, unsigned int flags) { struct fuse_inode *fi = get_fuse_inode(inode); @@ -3183,5 +3183,5 @@ void fuse_init_file_inode(struct inode *inode) fi->writepages = RB_ROOT; if (IS_ENABLED(CONFIG_FUSE_DAX)) - fuse_dax_inode_init(inode); + fuse_dax_inode_init(inode, flags); } diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h index 19ded93cfc49..f03ea7cb74b0 100644 --- a/fs/fuse/fuse_i.h +++ b/fs/fuse/fuse_i.h @@ -1022,7 +1022,7 @@ int fuse_notify_poll_wakeup(struct fuse_conn *fc, /** * Initialize file operations on a regular file */ -void fuse_init_file_inode(struct inode *inode); +void fuse_init_file_inode(struct inode *inode, unsigned int flags); /** * Initialize inode operations on regular files and special files @@ -1288,7 +1288,7 @@ int fuse_dax_conn_alloc(struct fuse_conn *fc, enum fuse_dax_mode mode, struct dax_device *dax_dev); void fuse_dax_conn_free(struct fuse_conn *fc); bool fuse_dax_inode_alloc(struct super_block *sb, struct fuse_inode *fi); -void fuse_dax_inode_init(struct inode *inode); +void fuse_dax_inode_init(struct inode *inode, unsigned int flags); void fuse_dax_inode_cleanup(struct inode *inode); bool fuse_dax_check_alignment(struct fuse_conn *fc, unsigned int map_alignment); void fuse_dax_cancel_work(struct fuse_conn *fc); diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c index 4a41e6a73f3f..0669e41a9645 100644 --- a/fs/fuse/inode.c +++ b/fs/fuse/inode.c @@ -313,7 +313,7 @@ static void fuse_init_inode(struct inode *inode, struct fuse_attr *attr) inode->i_ctime.tv_nsec = attr->ctimensec; if (S_ISREG(inode->i_mode)) { fuse_init_common(inode); - fuse_init_file_inode(inode); + fuse_init_file_inode(inode, attr->flags); } else if (S_ISDIR(inode->i_mode)) fuse_init_dir(inode); else if (S_ISLNK(inode->i_mode))
DAX may be limited in some specific situation. When the number of usable DAX windows is under watermark, the recalim routine will be triggered to reclaim some DAX windows. It may have a negative impact on the performance, since some processes may need to wait for DAX windows to be recalimed and reused then. To mitigate the performance degradation, the overall DAX window need to be expanded larger. However, simply expanding the DAX window may not be a good deal in some scenario. To maintain one DAX window chunk (i.e., 2MB in size), 32KB (512 * 64 bytes) memory footprint will be consumed for page descriptors inside guest, which is greater than the memory footprint if it uses guest page cache when DAX disabled. Thus it'd better disable DAX for those files smaller than 32KB, to reduce the demand for DAX window and thus avoid the unworthy memory overhead. Per inode DAX feature is introduced to address this issue, by offering a finer grained control for dax to users, trying to achieve a balance between performance and memory overhead. The FUSE_ATTR_DAX flag in FUSE_LOOKUP reply is used to indicate whether DAX should be enabled or not for corresponding file. Currently the state whether DAX is enabled or not for the file is initialized only when inode is instantiated. Signed-off-by: Jeffle Xu <jefflexu@linux.alibaba.com> --- fs/fuse/dax.c | 12 ++++++++---- fs/fuse/file.c | 4 ++-- fs/fuse/fuse_i.h | 4 ++-- fs/fuse/inode.c | 2 +- 4 files changed, 13 insertions(+), 9 deletions(-)