diff mbox series

[v4,02/18] mm/filemap: Remove dynamically allocated array from filemap_read

Message ID 20210121041616.3955703-3-willy@infradead.org (mailing list archive)
State New
Headers show
Series Refactor generic_file_buffered_read | expand

Commit Message

Matthew Wilcox Jan. 21, 2021, 4:16 a.m. UTC
Increasing the batch size runs into diminishing returns.  It's probably
better to make, eg, three calls to filemap_get_pages() than it is to
call into kmalloc().

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
 mm/filemap.c | 15 ++-------------
 1 file changed, 2 insertions(+), 13 deletions(-)

Comments

Christoph Hellwig Jan. 21, 2021, 7:31 a.m. UTC | #1
On Thu, Jan 21, 2021 at 04:16:00AM +0000, Matthew Wilcox (Oracle) wrote:
> Increasing the batch size runs into diminishing returns.  It's probably
> better to make, eg, three calls to filemap_get_pages() than it is to
> call into kmalloc().
> 
> Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>

Looks good,

Reviewed-by: Christoph Hellwig <hch@lst.de>
Miaohe Lin Jan. 22, 2021, 6:59 a.m. UTC | #2
Hi:
On 2021/1/21 12:16, Matthew Wilcox (Oracle) wrote:
> Increasing the batch size runs into diminishing returns.  It's probably
> better to make, eg, three calls to filemap_get_pages() than it is to
> call into kmalloc().
> 

LGTM. Thanks.

Reviewed-by: Miaohe Lin <linmiaohe@huawei.com>

> Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
> ---
>  mm/filemap.c | 15 ++-------------
>  1 file changed, 2 insertions(+), 13 deletions(-)
> 
> diff --git a/mm/filemap.c b/mm/filemap.c
> index 934e04f1760ef..5dec04c8e16b0 100644
> --- a/mm/filemap.c
> +++ b/mm/filemap.c
> @@ -2421,8 +2421,8 @@ ssize_t generic_file_buffered_read(struct kiocb *iocb,
>  	struct file_ra_state *ra = &filp->f_ra;
>  	struct address_space *mapping = filp->f_mapping;
>  	struct inode *inode = mapping->host;
> -	struct page *pages_onstack[PAGEVEC_SIZE], **pages = NULL;
> -	unsigned int nr_pages = min_t(unsigned int, 512,
> +	struct page *pages[PAGEVEC_SIZE];
> +	unsigned int nr_pages = min_t(unsigned int, PAGEVEC_SIZE,
>  			((iocb->ki_pos + iter->count + PAGE_SIZE - 1) >> PAGE_SHIFT) -
>  			(iocb->ki_pos >> PAGE_SHIFT));
>  	int i, pg_nr, error = 0;
> @@ -2433,14 +2433,6 @@ ssize_t generic_file_buffered_read(struct kiocb *iocb,
>  		return 0;
>  	iov_iter_truncate(iter, inode->i_sb->s_maxbytes);
>  
> -	if (nr_pages > ARRAY_SIZE(pages_onstack))
> -		pages = kmalloc_array(nr_pages, sizeof(void *), GFP_KERNEL);
> -
> -	if (!pages) {
> -		pages = pages_onstack;
> -		nr_pages = min_t(unsigned int, nr_pages, ARRAY_SIZE(pages_onstack));
> -	}
> -
>  	do {
>  		cond_resched();
>  
> @@ -2525,9 +2517,6 @@ ssize_t generic_file_buffered_read(struct kiocb *iocb,
>  
>  	file_accessed(filp);
>  
> -	if (pages != pages_onstack)
> -		kfree(pages);
> -
>  	return written ? written : error;
>  }
>  EXPORT_SYMBOL_GPL(generic_file_buffered_read);
>
diff mbox series

Patch

diff --git a/mm/filemap.c b/mm/filemap.c
index 934e04f1760ef..5dec04c8e16b0 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -2421,8 +2421,8 @@  ssize_t generic_file_buffered_read(struct kiocb *iocb,
 	struct file_ra_state *ra = &filp->f_ra;
 	struct address_space *mapping = filp->f_mapping;
 	struct inode *inode = mapping->host;
-	struct page *pages_onstack[PAGEVEC_SIZE], **pages = NULL;
-	unsigned int nr_pages = min_t(unsigned int, 512,
+	struct page *pages[PAGEVEC_SIZE];
+	unsigned int nr_pages = min_t(unsigned int, PAGEVEC_SIZE,
 			((iocb->ki_pos + iter->count + PAGE_SIZE - 1) >> PAGE_SHIFT) -
 			(iocb->ki_pos >> PAGE_SHIFT));
 	int i, pg_nr, error = 0;
@@ -2433,14 +2433,6 @@  ssize_t generic_file_buffered_read(struct kiocb *iocb,
 		return 0;
 	iov_iter_truncate(iter, inode->i_sb->s_maxbytes);
 
-	if (nr_pages > ARRAY_SIZE(pages_onstack))
-		pages = kmalloc_array(nr_pages, sizeof(void *), GFP_KERNEL);
-
-	if (!pages) {
-		pages = pages_onstack;
-		nr_pages = min_t(unsigned int, nr_pages, ARRAY_SIZE(pages_onstack));
-	}
-
 	do {
 		cond_resched();
 
@@ -2525,9 +2517,6 @@  ssize_t generic_file_buffered_read(struct kiocb *iocb,
 
 	file_accessed(filp);
 
-	if (pages != pages_onstack)
-		kfree(pages);
-
 	return written ? written : error;
 }
 EXPORT_SYMBOL_GPL(generic_file_buffered_read);