| Message ID | c390879ab020c44be25de8a07e3f1f87402350e0.1729072803.git.baolin.wang@linux.alibaba.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | Improve the tmpfs large folio read performance | expand |
On 2024/10/16 18:09, Baolin Wang wrote: > Use iocb->ki_pos to check if the read bytes exceeds the file size and to > calculate the bytes to be read can help simplify the code logic. Meanwhile, > this is also a preparation for improving tmpfs large folios read performace > in the following patch. > > Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com> > --- > mm/shmem.c | 36 ++++++++++++------------------------ > 1 file changed, 12 insertions(+), 24 deletions(-) > > diff --git a/mm/shmem.c b/mm/shmem.c > index 66eae800ffab..edab02a26aac 100644 > --- a/mm/shmem.c > +++ b/mm/shmem.c > @@ -3106,26 +3106,18 @@ static ssize_t shmem_file_read_iter(struct kiocb *iocb, struct iov_iter *to) > unsigned long offset; > int error = 0; > ssize_t retval = 0; > - loff_t *ppos = &iocb->ki_pos; > > - index = *ppos >> PAGE_SHIFT; > - offset = *ppos & ~PAGE_MASK; > + index = iocb->ki_pos >> PAGE_SHIFT; index calculate could be moved before shmem_get_folio(), then... > + offset = iocb->ki_pos & ~PAGE_MASK; > > for (;;) { > struct folio *folio = NULL; > struct page *page = NULL; > - pgoff_t end_index; > unsigned long nr, ret; > - loff_t i_size = i_size_read(inode); > + loff_t end_offset, i_size = i_size_read(inode); > > - end_index = i_size >> PAGE_SHIFT; > - if (index > end_index) > + if (unlikely(iocb->ki_pos >= i_size)) > break; > - if (index == end_index) { > - nr = i_size & ~PAGE_MASK; > - if (nr <= offset) > - break; > - } > > error = shmem_get_folio(inode, index, 0, &folio, SGP_READ); > if (error) { > @@ -3148,18 +3140,14 @@ static ssize_t shmem_file_read_iter(struct kiocb *iocb, struct iov_iter *to) > * We must evaluate after, since reads (unlike writes) > * are called without i_rwsem protection against truncate > */ > - nr = PAGE_SIZE; > i_size = i_size_read(inode); > - end_index = i_size >> PAGE_SHIFT; > - if (index == end_index) { > - nr = i_size & ~PAGE_MASK; > - if (nr <= offset) { > - if (folio) > - folio_put(folio); > - break; > - } > + if (unlikely(iocb->ki_pos >= i_size)) { > + if (folio) > + folio_put(folio); > + break; > } > - nr -= offset; > + end_offset = min_t(loff_t, i_size, iocb->ki_pos + to->count); > + nr = min_t(loff_t, end_offset - iocb->ki_pos, PAGE_SIZE - offset); > > if (folio) { > /* > @@ -3199,8 +3187,9 @@ static ssize_t shmem_file_read_iter(struct kiocb *iocb, struct iov_iter *to) > > retval += ret; > offset += ret; > - index += offset >> PAGE_SHIFT; > offset &= ~PAGE_MASK; > + iocb->ki_pos += ret; > + index = iocb->ki_pos >> PAGE_SHIFT; remove this line. > > if (!iov_iter_count(to)) > break; > @@ -3211,7 +3200,6 @@ static ssize_t shmem_file_read_iter(struct kiocb *iocb, struct iov_iter *to) > cond_resched(); > } > > - *ppos = ((loff_t) index << PAGE_SHIFT) + offset; > file_accessed(file); > return retval ? retval : error; > }
On 2024/10/16 20:34, Kefeng Wang wrote: > > > On 2024/10/16 18:09, Baolin Wang wrote: >> Use iocb->ki_pos to check if the read bytes exceeds the file size and to >> calculate the bytes to be read can help simplify the code logic. >> Meanwhile, >> this is also a preparation for improving tmpfs large folios read >> performace >> in the following patch. >> >> Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com> >> --- >> mm/shmem.c | 36 ++++++++++++------------------------ >> 1 file changed, 12 insertions(+), 24 deletions(-) >> >> diff --git a/mm/shmem.c b/mm/shmem.c >> index 66eae800ffab..edab02a26aac 100644 >> --- a/mm/shmem.c >> +++ b/mm/shmem.c >> @@ -3106,26 +3106,18 @@ static ssize_t shmem_file_read_iter(struct >> kiocb *iocb, struct iov_iter *to) >> unsigned long offset; >> int error = 0; >> ssize_t retval = 0; >> - loff_t *ppos = &iocb->ki_pos; >> - index = *ppos >> PAGE_SHIFT; >> - offset = *ppos & ~PAGE_MASK; >> + index = iocb->ki_pos >> PAGE_SHIFT; > > index calculate could be moved before shmem_get_folio(), then... Yes. Will do.
diff --git a/mm/shmem.c b/mm/shmem.c index 66eae800ffab..edab02a26aac 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -3106,26 +3106,18 @@ static ssize_t shmem_file_read_iter(struct kiocb *iocb, struct iov_iter *to) unsigned long offset; int error = 0; ssize_t retval = 0; - loff_t *ppos = &iocb->ki_pos; - index = *ppos >> PAGE_SHIFT; - offset = *ppos & ~PAGE_MASK; + index = iocb->ki_pos >> PAGE_SHIFT; + offset = iocb->ki_pos & ~PAGE_MASK; for (;;) { struct folio *folio = NULL; struct page *page = NULL; - pgoff_t end_index; unsigned long nr, ret; - loff_t i_size = i_size_read(inode); + loff_t end_offset, i_size = i_size_read(inode); - end_index = i_size >> PAGE_SHIFT; - if (index > end_index) + if (unlikely(iocb->ki_pos >= i_size)) break; - if (index == end_index) { - nr = i_size & ~PAGE_MASK; - if (nr <= offset) - break; - } error = shmem_get_folio(inode, index, 0, &folio, SGP_READ); if (error) { @@ -3148,18 +3140,14 @@ static ssize_t shmem_file_read_iter(struct kiocb *iocb, struct iov_iter *to) * We must evaluate after, since reads (unlike writes) * are called without i_rwsem protection against truncate */ - nr = PAGE_SIZE; i_size = i_size_read(inode); - end_index = i_size >> PAGE_SHIFT; - if (index == end_index) { - nr = i_size & ~PAGE_MASK; - if (nr <= offset) { - if (folio) - folio_put(folio); - break; - } + if (unlikely(iocb->ki_pos >= i_size)) { + if (folio) + folio_put(folio); + break; } - nr -= offset; + end_offset = min_t(loff_t, i_size, iocb->ki_pos + to->count); + nr = min_t(loff_t, end_offset - iocb->ki_pos, PAGE_SIZE - offset); if (folio) { /* @@ -3199,8 +3187,9 @@ static ssize_t shmem_file_read_iter(struct kiocb *iocb, struct iov_iter *to) retval += ret; offset += ret; - index += offset >> PAGE_SHIFT; offset &= ~PAGE_MASK; + iocb->ki_pos += ret; + index = iocb->ki_pos >> PAGE_SHIFT; if (!iov_iter_count(to)) break; @@ -3211,7 +3200,6 @@ static ssize_t shmem_file_read_iter(struct kiocb *iocb, struct iov_iter *to) cond_resched(); } - *ppos = ((loff_t) index << PAGE_SHIFT) + offset; file_accessed(file); return retval ? retval : error; }
Use iocb->ki_pos to check if the read bytes exceeds the file size and to calculate the bytes to be read can help simplify the code logic. Meanwhile, this is also a preparation for improving tmpfs large folios read performace in the following patch. Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com> --- mm/shmem.c | 36 ++++++++++++------------------------ 1 file changed, 12 insertions(+), 24 deletions(-)