From: Tejun Heo <tj@kernel.org> To: axboe@kernel.dk Cc: linux-kernel@vger.kernel.org, jack@suse.cz, hch@infradead.org, hannes@cmpxchg.org, linux-fsdevel@vger.kernel.org, vgoyal@redhat.com, lizefan@huawei.com, cgroups@vger.kernel.org, linux-mm@kvack.org, mhocko@suse.cz, clm@fb.com, fengguang.wu@intel.com, david@fromorbit.com, gthelen@google.com, Tejun Heo <tj@kernel.org> Subject: [PATCH 10/10] writeback: disassociate inodes from dying bdi_writebacks Date: Mon, 6 Apr 2015 16:18:28 -0400 [thread overview] Message-ID: <1428351508-8399-11-git-send-email-tj@kernel.org> (raw) In-Reply-To: <1428351508-8399-1-git-send-email-tj@kernel.org> For the purpose of foreign inode detection, wb's (bdi_writeback's) are identified by the associated memcg ID. As we create a separate wb for each memcg, this is enough to identify the active wb's; however, when blkcg is enabled or disabled higher up in the hierarchy, the mapping between memcg and blkcg changes which in turn creates a new wb to service the new mapping. The old wb is unlinked from index and released after all references are drained. The foreign inode detection logic can't detect this condition because both the old and new wb's point to the same memcg and thus never decides to move inodes attached to the old wb to the new one. This patch adds logic to initiate switching immediately in wbc_attach_and_unlock_inode() if the associated wb is dying. We can make the usual foreign detection logic to distinguish the different wb's mapped to the memcg but the dying wb is never gonna be in active service again and there's no point in tracking the usage history and reaching the switch verdict after enough data points are collected. It's already known that the wb has to be switched. Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Jens Axboe <axboe@kernel.dk> Cc: Jan Kara <jack@suse.cz> Cc: Wu Fengguang <fengguang.wu@intel.com> Cc: Greg Thelen <gthelen@google.com> --- fs/fs-writeback.c | 7 +++++++ include/linux/backing-dev-defs.h | 16 ++++++++++++++++ 2 files changed, 23 insertions(+) diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c index 74b7a99..6c9dae0 100644 --- a/fs/fs-writeback.c +++ b/fs/fs-writeback.c @@ -512,6 +512,13 @@ void wbc_attach_and_unlock_inode(struct writeback_control *wbc, wb_get(wbc->wb); spin_unlock(&inode->i_lock); + + /* + * A dying wb indicates that the memcg-blkcg mapping has changed + * and a new wb is already serving the memcg. Switch immediately. + */ + if (unlikely(wb_dying(wbc->wb))) + inode_switch_wbs(inode, wbc->wb_id); } /** diff --git a/include/linux/backing-dev-defs.h b/include/linux/backing-dev-defs.h index e047b49..a48d90e 100644 --- a/include/linux/backing-dev-defs.h +++ b/include/linux/backing-dev-defs.h @@ -219,6 +219,17 @@ static inline void wb_put(struct bdi_writeback *wb) percpu_ref_put(&wb->refcnt); } +/** + * wb_dying - is a wb dying? + * @wb: bdi_writeback of interest + * + * Returns whether @wb is unlinked and being drained. + */ +static inline bool wb_dying(struct bdi_writeback *wb) +{ + return percpu_ref_is_dying(&wb->refcnt); +} + #else /* CONFIG_CGROUP_WRITEBACK */ static inline bool wb_tryget(struct bdi_writeback *wb) @@ -234,6 +245,11 @@ static inline void wb_put(struct bdi_writeback *wb) { } +static inline bool wb_dying(struct bdi_writeback *wb) +{ + return false; +} + #endif /* CONFIG_CGROUP_WRITEBACK */ #endif /* __LINUX_BACKING_DEV_DEFS_H */ -- 2.1.0
WARNING: multiple messages have this Message-ID (diff)
From: Tejun Heo <tj@kernel.org> To: axboe@kernel.dk Cc: linux-kernel@vger.kernel.org, jack@suse.cz, hch@infradead.org, hannes@cmpxchg.org, linux-fsdevel@vger.kernel.org, vgoyal@redhat.com, lizefan@huawei.com, cgroups@vger.kernel.org, linux-mm@kvack.org, mhocko@suse.cz, clm@fb.com, fengguang.wu@intel.com, david@fromorbit.com, gthelen@google.com, Tejun Heo <tj@kernel.org> Subject: [PATCH 10/10] writeback: disassociate inodes from dying bdi_writebacks Date: Mon, 6 Apr 2015 16:18:28 -0400 [thread overview] Message-ID: <1428351508-8399-11-git-send-email-tj@kernel.org> (raw) In-Reply-To: <1428351508-8399-1-git-send-email-tj@kernel.org> For the purpose of foreign inode detection, wb's (bdi_writeback's) are identified by the associated memcg ID. As we create a separate wb for each memcg, this is enough to identify the active wb's; however, when blkcg is enabled or disabled higher up in the hierarchy, the mapping between memcg and blkcg changes which in turn creates a new wb to service the new mapping. The old wb is unlinked from index and released after all references are drained. The foreign inode detection logic can't detect this condition because both the old and new wb's point to the same memcg and thus never decides to move inodes attached to the old wb to the new one. This patch adds logic to initiate switching immediately in wbc_attach_and_unlock_inode() if the associated wb is dying. We can make the usual foreign detection logic to distinguish the different wb's mapped to the memcg but the dying wb is never gonna be in active service again and there's no point in tracking the usage history and reaching the switch verdict after enough data points are collected. It's already known that the wb has to be switched. Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Jens Axboe <axboe@kernel.dk> Cc: Jan Kara <jack@suse.cz> Cc: Wu Fengguang <fengguang.wu@intel.com> Cc: Greg Thelen <gthelen@google.com> --- fs/fs-writeback.c | 7 +++++++ include/linux/backing-dev-defs.h | 16 ++++++++++++++++ 2 files changed, 23 insertions(+) diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c index 74b7a99..6c9dae0 100644 --- a/fs/fs-writeback.c +++ b/fs/fs-writeback.c @@ -512,6 +512,13 @@ void wbc_attach_and_unlock_inode(struct writeback_control *wbc, wb_get(wbc->wb); spin_unlock(&inode->i_lock); + + /* + * A dying wb indicates that the memcg-blkcg mapping has changed + * and a new wb is already serving the memcg. Switch immediately. + */ + if (unlikely(wb_dying(wbc->wb))) + inode_switch_wbs(inode, wbc->wb_id); } /** diff --git a/include/linux/backing-dev-defs.h b/include/linux/backing-dev-defs.h index e047b49..a48d90e 100644 --- a/include/linux/backing-dev-defs.h +++ b/include/linux/backing-dev-defs.h @@ -219,6 +219,17 @@ static inline void wb_put(struct bdi_writeback *wb) percpu_ref_put(&wb->refcnt); } +/** + * wb_dying - is a wb dying? + * @wb: bdi_writeback of interest + * + * Returns whether @wb is unlinked and being drained. + */ +static inline bool wb_dying(struct bdi_writeback *wb) +{ + return percpu_ref_is_dying(&wb->refcnt); +} + #else /* CONFIG_CGROUP_WRITEBACK */ static inline bool wb_tryget(struct bdi_writeback *wb) @@ -234,6 +245,11 @@ static inline void wb_put(struct bdi_writeback *wb) { } +static inline bool wb_dying(struct bdi_writeback *wb) +{ + return false; +} + #endif /* CONFIG_CGROUP_WRITEBACK */ #endif /* __LINUX_BACKING_DEV_DEFS_H */ -- 2.1.0 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
next prev parent reply other threads:[~2015-04-06 20:19 UTC|newest] Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top 2015-04-06 20:18 [PATCHSET 3/3 v2 block/for-4.1/core] writeback: implement foreign cgroup inode bdi_writeback switching Tejun Heo 2015-04-06 20:18 ` Tejun Heo 2015-04-06 20:18 ` [PATCH 01/10] writeback: relocate wb[_try]_get(), wb_put(), inode_{attach|detach}_wb() Tejun Heo 2015-04-06 20:18 ` Tejun Heo 2015-04-06 20:18 ` [PATCH 02/10] writeback: make writeback_control track the inode being written back Tejun Heo 2015-04-06 20:18 ` Tejun Heo 2015-04-06 20:18 ` [PATCH 03/10] writeback: implement foreign cgroup inode detection Tejun Heo 2015-04-06 20:18 ` Tejun Heo 2015-04-06 20:18 ` [PATCH 04/10] truncate: swap the order of conditionals in cancel_dirty_page() Tejun Heo 2015-04-06 20:18 ` Tejun Heo 2015-04-06 20:18 ` [PATCH 05/10] writeback: implement [locked_]inode_to_wb_and_lock_list() Tejun Heo 2015-04-06 20:18 ` Tejun Heo 2015-04-06 20:18 ` [PATCH 06/10] writeback: implement unlocked_inode_to_wb transaction and use it for stat updates Tejun Heo 2015-04-06 20:18 ` Tejun Heo 2015-04-06 20:18 ` [PATCH 07/10] writeback: use unlocked_inode_to_wb transaction in inode_congested() Tejun Heo 2015-04-06 20:18 ` Tejun Heo 2015-04-06 20:18 ` [PATCH 08/10] writeback: add lockdep annotation to inode_to_wb() Tejun Heo 2015-04-06 20:18 ` Tejun Heo 2015-04-06 20:18 ` [PATCH 09/10] writeback: implement foreign cgroup inode bdi_writeback switching Tejun Heo 2015-04-06 20:18 ` Tejun Heo 2015-04-06 20:18 ` Tejun Heo [this message] 2015-04-06 20:18 ` [PATCH 10/10] writeback: disassociate inodes from dying bdi_writebacks Tejun Heo
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