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    SubjectRe: [PATCH v6 4/9] memcg: add kernel calls for memcg dirty page stats
    On Fri, Mar 11, 2011 at 10:43:26AM -0800, Greg Thelen wrote:
    > Add calls into memcg dirty page accounting. Notify memcg when pages
    > transition between clean, file dirty, writeback, and unstable nfs.
    > This allows the memory controller to maintain an accurate view of
    > the amount of its memory that is dirty.
    >
    > Signed-off-by: Greg Thelen <gthelen@google.com>
    > Signed-off-by: Andrea Righi <arighi@develer.com>
    > Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
    > Reviewed-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
    > ---
    > Changelog since v5:
    > - moved accounting site in test_clear_page_writeback() and
    > test_set_page_writeback().
    >
    > fs/nfs/write.c | 4 ++++
    > mm/filemap.c | 1 +
    > mm/page-writeback.c | 10 ++++++++--
    > mm/truncate.c | 1 +
    > 4 files changed, 14 insertions(+), 2 deletions(-)
    >
    > diff --git a/fs/nfs/write.c b/fs/nfs/write.c
    > index 42b92d7..7863777 100644
    > --- a/fs/nfs/write.c
    > +++ b/fs/nfs/write.c
    > @@ -451,6 +451,7 @@ nfs_mark_request_commit(struct nfs_page *req)
    > NFS_PAGE_TAG_COMMIT);
    > nfsi->ncommit++;
    > spin_unlock(&inode->i_lock);
    > + mem_cgroup_inc_page_stat(req->wb_page, MEMCG_NR_FILE_UNSTABLE_NFS);
    > inc_zone_page_state(req->wb_page, NR_UNSTABLE_NFS);
    > inc_bdi_stat(req->wb_page->mapping->backing_dev_info, BDI_RECLAIMABLE);
    > __mark_inode_dirty(inode, I_DIRTY_DATASYNC);
    > @@ -462,6 +463,7 @@ nfs_clear_request_commit(struct nfs_page *req)
    > struct page *page = req->wb_page;
    >
    > if (test_and_clear_bit(PG_CLEAN, &(req)->wb_flags)) {
    > + mem_cgroup_dec_page_stat(page, MEMCG_NR_FILE_UNSTABLE_NFS);
    > dec_zone_page_state(page, NR_UNSTABLE_NFS);
    > dec_bdi_stat(page->mapping->backing_dev_info, BDI_RECLAIMABLE);
    > return 1;
    > @@ -1319,6 +1321,8 @@ nfs_commit_list(struct inode *inode, struct list_head *head, int how)
    > req = nfs_list_entry(head->next);
    > nfs_list_remove_request(req);
    > nfs_mark_request_commit(req);
    > + mem_cgroup_dec_page_stat(req->wb_page,
    > + MEMCG_NR_FILE_UNSTABLE_NFS);
    > dec_zone_page_state(req->wb_page, NR_UNSTABLE_NFS);
    > dec_bdi_stat(req->wb_page->mapping->backing_dev_info,
    > BDI_RECLAIMABLE);
    > diff --git a/mm/filemap.c b/mm/filemap.c
    > index a6cfecf..7e751fe 100644
    > --- a/mm/filemap.c
    > +++ b/mm/filemap.c
    > @@ -143,6 +143,7 @@ void __delete_from_page_cache(struct page *page)
    > * having removed the page entirely.
    > */
    > if (PageDirty(page) && mapping_cap_account_dirty(mapping)) {
    > + mem_cgroup_dec_page_stat(page, MEMCG_NR_FILE_DIRTY);
    > dec_zone_page_state(page, NR_FILE_DIRTY);
    > dec_bdi_stat(mapping->backing_dev_info, BDI_RECLAIMABLE);
    > }
    > diff --git a/mm/page-writeback.c b/mm/page-writeback.c
    > index 632b464..d8005b0 100644
    > --- a/mm/page-writeback.c
    > +++ b/mm/page-writeback.c
    > @@ -1118,6 +1118,7 @@ int __set_page_dirty_no_writeback(struct page *page)
    > void account_page_dirtied(struct page *page, struct address_space *mapping)
    > {
    > if (mapping_cap_account_dirty(mapping)) {
    > + mem_cgroup_inc_page_stat(page, MEMCG_NR_FILE_DIRTY);
    > __inc_zone_page_state(page, NR_FILE_DIRTY);
    > __inc_zone_page_state(page, NR_DIRTIED);
    > __inc_bdi_stat(mapping->backing_dev_info, BDI_RECLAIMABLE);
    > @@ -1317,6 +1318,7 @@ int clear_page_dirty_for_io(struct page *page)
    > * for more comments.
    > */
    > if (TestClearPageDirty(page)) {
    > + mem_cgroup_dec_page_stat(page, MEMCG_NR_FILE_DIRTY);
    > dec_zone_page_state(page, NR_FILE_DIRTY);
    > dec_bdi_stat(mapping->backing_dev_info,
    > BDI_RECLAIMABLE);
    > @@ -1352,8 +1354,10 @@ int test_clear_page_writeback(struct page *page)
    > } else {
    > ret = TestClearPageWriteback(page);
    > }
    > - if (ret)
    > + if (ret) {
    > + mem_cgroup_dec_page_stat(page, MEMCG_NR_FILE_WRITEBACK);
    > dec_zone_page_state(page, NR_WRITEBACK);
    > + }
    > return ret;
    > }
    >
    > @@ -1386,8 +1390,10 @@ int test_set_page_writeback(struct page *page)
    > } else {
    > ret = TestSetPageWriteback(page);
    > }
    > - if (!ret)
    > + if (!ret) {
    > + mem_cgroup_inc_page_stat(page, MEMCG_NR_FILE_WRITEBACK);
    > account_page_writeback(page);
    > + }
    > return ret;
    >
    > }

    At least in mainline, NR_WRITEBACK handling codes are following as.

    1) increase

    * account_page_writeback

    2) decrease

    * test_clear_page_writeback
    * __nilfs_end_page_io

    I think account_page_writeback name is good to add your account function into that.
    The problem is decreasement. Normall we can handle decreasement in test_clear_page_writeback.
    But I am not sure it's okay in __nilfs_end_page_io.
    I think if __nilfs_end_page_io is right, __nilfs_end_page_io should call
    mem_cgroup_dec_page_stat(page, MEMCG_NR_FILE_WRITEBACK).

    What do you think about it?



    --
    Kind regards,
    Minchan Kim


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