Hello,
On Sat, Feb 23, 2013 at 05:58:00PM -0500, Phillip Susi wrote:
> The previous implementation initiated writeout for a non congested bdi, and
> then discarded any clean pages. This had 3 problems:
>
> 1) The writeout would spin up the disk unnecessarily
> 2) Discarding pages under low cache pressure is a waste
> 3) It was useless on files being written, and thus full of dirty pages
>
> Now we just move the pages to the inactive list so they will be reclaimed
> sooner.
> ---
> include/linux/fs.h | 2 ++
> mm/fadvise.c | 8 ++------
> mm/filemap.c | 43 +++++++++++++++++++++++++++++++++++++++++++
> 3 files changed, 47 insertions(+), 6 deletions(-)
>
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index 7d2e893..2abd193 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -2198,6 +2198,8 @@ extern int __filemap_fdatawrite_range(struct address_space *mapping,
> loff_t start, loff_t end, int sync_mode);
> extern int filemap_fdatawrite_range(struct address_space *mapping,
> loff_t start, loff_t end);
> +extern void filemap_deactivate_range(struct address_space *mapping, pgoff_t start,
> + pgoff_t end);
>
> extern int vfs_fsync_range(struct file *file, loff_t start, loff_t end,
> int datasync);
> diff --git a/mm/fadvise.c b/mm/fadvise.c
> index a47f0f5..fbd58b0 100644
> --- a/mm/fadvise.c
> +++ b/mm/fadvise.c
> @@ -112,17 +112,13 @@ SYSCALL_DEFINE(fadvise64_64)(int fd, loff_t offset, loff_t len, int advice)
> case POSIX_FADV_NOREUSE:
> break;
> case POSIX_FADV_DONTNEED:
> - if (!bdi_write_congested(mapping->backing_dev_info))
> - __filemap_fdatawrite_range(mapping, offset, endbyte,
> - WB_SYNC_NONE);
> -
> /* First and last FULL page! */
> start_index = (offset+(PAGE_CACHE_SIZE-1)) >> PAGE_CACHE_SHIFT;
> end_index = (endbyte >> PAGE_CACHE_SHIFT);
>
> if (end_index >= start_index)
> - invalidate_mapping_pages(mapping, start_index,
> - end_index);
> + filemap_deactivate_range(mapping, start_index,
> + end_index);
> break;
> default:
> ret = -EINVAL;
> diff --git a/mm/filemap.c b/mm/filemap.c
> index c610076..bcdcdbf 100644
> --- a/mm/filemap.c
> +++ b/mm/filemap.c
> @@ -217,7 +217,49 @@ int __filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
> return ret;
> }
>
> +/**
> + * filemap_deactivate_range - moves pages in range to the inactive list
> + * @mapping: the address_space which holds the pages to deactivate
> + * @start: offset where the range starts
> + * @end: offset where the range ends (inclusive)
> + */
> +void filemap_deactivate_range(struct address_space *mapping, pgoff_t start,
> + pgoff_t end)
> +{
> + struct pagevec pvec;
> + pgoff_t index = start;
> + int i;
> +
> + /*
> + * Note: this function may get called on a shmem/tmpfs mapping:
> + * pagevec_lookup() might then return 0 prematurely (because it
> + * got a gangful of swap entries); but it's hardly worth worrying
> + * about - it can rarely have anything to free from such a mapping
> + * (most pages are dirty), and already skips over any difficulties.
> + */
> +
> + pagevec_init(&pvec, 0);
> + while (index <= end && pagevec_lookup(&pvec, mapping, index,
> + min(end - index, (pgoff_t)PAGEVEC_SIZE - 1) + 1)) {
> + mem_cgroup_uncharge_start();
> + for (i = 0; i < pagevec_count(&pvec); i++) {
> + struct page *page = pvec.pages[i];
> +
> + /* We rely upon deletion not changing page->index */
> + index = page->index;
> + if (index > end)
> + break;
> +
> + WARN_ON(page->index != index);
> + deactivate_page(page);
> + }
> + pagevec_release(&pvec);
> + mem_cgroup_uncharge_end();
> + cond_resched();
> + index++;
> + }
> +}
> +
> static inline int __filemap_fdatawrite(struct address_space *mapping,
> int sync_mode)
> {
> --
> 1.8.1.2
>
Just FYI,
there was a person tried to solve similar problem, Andrea Righi. Ccing him,
Personally, I like this but unfortunately maintainer didn't like it
due to breaking compatibility and I understand.
https://lkml.org/lkml/2011/6/28/468
You might need another round with akpm. :(
--
Kind regards,
Minchan Kim
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