From: Tejun Heo <tj@kernel.org>
To: Vivek Goyal <vgoyal@redhat.com>
Cc: axboe@kernel.dk, linux-kernel@vger.kernel.org, jack@suse.cz,
hch@infradead.org, hannes@cmpxchg.org,
linux-fsdevel@vger.kernel.org, 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
Subject: Re: [PATCH 21/48] writeback: make backing_dev_info host cgroup-specific bdi_writebacks
Date: Fri, 27 Mar 2015 17:41:54 -0400 [thread overview]
Message-ID: <20150327214154.GE638@htj.duckdns.org> (raw)
In-Reply-To: <20150327210612.GA23840@redhat.com>
Hello Vivek.
On Fri, Mar 27, 2015 at 05:06:13PM -0400, Vivek Goyal wrote:
> I was curious to know that why do we need this "struct page *page" when
> trying to attach a inode to a bdi_writeback. Is using current's cgroup
> always not sufficient?
So, memcg's page ownership is first-use based and it never gets
updated once set till the page is released which means that there can
be corner cases where an inode is mostly faulted in by one cgroup and
then constantly dirtied by another. Because the ownership belongs to
the initial cgroup which instantiated those pages, cgroup writeback
ends up considering the pages as belonging to that initial cgroup and
the foreign detection will trigger if it's being written by a
different cgroup. Hmmmm... this isn't a huge problem as once the
foreign detection triggers, the problem will be corrected but still
when the page is availalbe, I think it makes sense to attach to the
page as that's what actually defines the ownership.
Thanks.
--
tejun
WARNING: multiple messages have this Message-ID (diff)
From: Tejun Heo <tj@kernel.org>
To: Vivek Goyal <vgoyal@redhat.com>
Cc: axboe@kernel.dk, linux-kernel@vger.kernel.org, jack@suse.cz,
hch@infradead.org, hannes@cmpxchg.org,
linux-fsdevel@vger.kernel.org, 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
Subject: Re: [PATCH 21/48] writeback: make backing_dev_info host cgroup-specific bdi_writebacks
Date: Fri, 27 Mar 2015 17:41:54 -0400 [thread overview]
Message-ID: <20150327214154.GE638@htj.duckdns.org> (raw)
In-Reply-To: <20150327210612.GA23840@redhat.com>
Hello Vivek.
On Fri, Mar 27, 2015 at 05:06:13PM -0400, Vivek Goyal wrote:
> I was curious to know that why do we need this "struct page *page" when
> trying to attach a inode to a bdi_writeback. Is using current's cgroup
> always not sufficient?
So, memcg's page ownership is first-use based and it never gets
updated once set till the page is released which means that there can
be corner cases where an inode is mostly faulted in by one cgroup and
then constantly dirtied by another. Because the ownership belongs to
the initial cgroup which instantiated those pages, cgroup writeback
ends up considering the pages as belonging to that initial cgroup and
the foreign detection will trigger if it's being written by a
different cgroup. Hmmmm... this isn't a huge problem as once the
foreign detection triggers, the problem will be corrected but still
when the page is availalbe, I think it makes sense to attach to the
page as that's what actually defines the ownership.
Thanks.
--
tejun
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next prev parent reply other threads:[~2015-03-27 21:42 UTC|newest]
Thread overview: 119+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-03-23 4:54 [PATCHSET 1/3 v2 block/for-4.1/core] writeback: cgroup writeback support Tejun Heo
2015-03-23 4:54 ` Tejun Heo
2015-03-23 4:54 ` [PATCH 01/48] memcg: add per cgroup dirty page accounting Tejun Heo
2015-03-23 4:54 ` Tejun Heo
2015-03-23 4:54 ` [PATCH 02/48] blkcg: move block/blk-cgroup.h to include/linux/blk-cgroup.h Tejun Heo
2015-03-23 4:54 ` Tejun Heo
2015-03-23 4:54 ` [PATCH 03/48] update !CONFIG_BLK_CGROUP dummies in include/linux/blk-cgroup.h Tejun Heo
2015-03-23 4:54 ` Tejun Heo
2015-03-23 4:54 ` Tejun Heo
2015-03-23 4:54 ` [PATCH 04/48] memcg: add mem_cgroup_root_css Tejun Heo
2015-03-23 4:54 ` Tejun Heo
2015-03-23 4:54 ` [PATCH 05/48] blkcg: add blkcg_root_css Tejun Heo
2015-03-23 4:54 ` Tejun Heo
2015-03-23 4:54 ` [PATCH 06/48] cgroup, block: implement task_get_css() and use it in bio_associate_current() Tejun Heo
2015-03-23 4:54 ` Tejun Heo
2015-03-23 4:54 ` [PATCH 07/48] blkcg: implement task_get_blkcg_css() Tejun Heo
2015-03-23 4:54 ` Tejun Heo
2015-03-23 4:54 ` [PATCH 08/48] blkcg: implement bio_associate_blkcg() Tejun Heo
2015-03-23 4:54 ` Tejun Heo
2015-03-23 4:54 ` [PATCH 09/48] memcg: implement mem_cgroup_css_from_page() Tejun Heo
2015-03-23 4:54 ` Tejun Heo
2015-03-23 4:54 ` [PATCH 10/48] writeback: move backing_dev_info->state into bdi_writeback Tejun Heo
2015-03-23 4:54 ` Tejun Heo
2015-03-23 4:54 ` [PATCH 11/48] writeback: move backing_dev_info->bdi_stat[] " Tejun Heo
2015-03-23 4:54 ` Tejun Heo
2015-03-23 4:54 ` [PATCH 12/48] writeback: move bandwidth related fields from backing_dev_info " Tejun Heo
2015-03-23 4:54 ` Tejun Heo
2015-03-23 4:54 ` [PATCH 13/48] writeback: s/bdi/wb/ in mm/page-writeback.c Tejun Heo
2015-03-23 4:54 ` Tejun Heo
2015-03-23 4:54 ` [PATCH 14/48] writeback: move backing_dev_info->wb_lock and ->worklist into bdi_writeback Tejun Heo
2015-03-23 4:54 ` Tejun Heo
2015-03-23 4:54 ` [PATCH 15/48] writeback: reorganize mm/backing-dev.c Tejun Heo
2015-03-23 4:54 ` Tejun Heo
2015-03-23 4:54 ` [PATCH 16/48] writeback: separate out include/linux/backing-dev-defs.h Tejun Heo
2015-03-23 4:54 ` Tejun Heo
2015-03-23 4:54 ` [PATCH 17/48] bdi: make inode_to_bdi() inline Tejun Heo
2015-03-23 4:54 ` Tejun Heo
2015-03-23 4:54 ` [PATCH 18/48] writeback: add @gfp to wb_init() Tejun Heo
2015-03-23 4:54 ` Tejun Heo
2015-03-23 4:54 ` [PATCH 19/48] bdi: separate out congested state into a separate struct Tejun Heo
2015-03-23 4:54 ` Tejun Heo
2015-03-23 4:54 ` [PATCH 20/48] writeback: add {CONFIG|BDI_CAP|FS}_CGROUP_WRITEBACK Tejun Heo
2015-03-23 4:54 ` Tejun Heo
2015-03-23 4:54 ` [PATCH 21/48] writeback: make backing_dev_info host cgroup-specific bdi_writebacks Tejun Heo
2015-03-23 4:54 ` Tejun Heo
2015-03-27 21:06 ` Vivek Goyal
2015-03-27 21:06 ` Vivek Goyal
2015-03-27 21:41 ` Tejun Heo [this message]
2015-03-27 21:41 ` Tejun Heo
2015-03-23 4:54 ` [PATCH 22/48] writeback, blkcg: associate each blkcg_gq with the corresponding bdi_writeback_congested Tejun Heo
2015-03-23 4:54 ` Tejun Heo
2015-03-23 4:54 ` [PATCH 23/48] writeback: attribute stats to the matching per-cgroup bdi_writeback Tejun Heo
2015-03-23 4:54 ` Tejun Heo
2015-03-23 4:54 ` Tejun Heo
2015-03-23 4:54 ` [PATCH 24/48] writeback: let balance_dirty_pages() work on the matching cgroup bdi_writeback Tejun Heo
2015-03-23 4:54 ` Tejun Heo
2015-03-23 4:54 ` [PATCH 25/48] writeback: make congestion functions per bdi_writeback Tejun Heo
2015-03-23 4:54 ` Tejun Heo
2015-03-23 4:54 ` [PATCH 26/48] writeback, blkcg: restructure blk_{set|clear}_queue_congested() Tejun Heo
2015-03-23 4:54 ` Tejun Heo
2015-03-23 4:54 ` [PATCH 27/48] writeback, blkcg: propagate non-root blkcg congestion state Tejun Heo
2015-03-23 4:54 ` Tejun Heo
2015-03-23 4:54 ` Tejun Heo
2015-03-23 4:54 ` [PATCH 28/48] writeback: implement and use mapping_congested() Tejun Heo
2015-03-23 4:54 ` Tejun Heo
2015-03-27 18:06 ` Vivek Goyal
2015-03-27 18:06 ` Vivek Goyal
2015-03-27 18:06 ` Vivek Goyal
2015-03-27 21:46 ` Tejun Heo
2015-03-27 21:46 ` Tejun Heo
2015-03-23 4:54 ` [PATCH 29/48] writeback: implement WB_has_dirty_io wb_state flag Tejun Heo
2015-03-23 4:54 ` Tejun Heo
2015-03-23 4:54 ` [PATCH 30/48] writeback: implement backing_dev_info->tot_write_bandwidth Tejun Heo
2015-03-23 4:54 ` Tejun Heo
2015-03-23 4:54 ` [PATCH 31/48] writeback: make bdi_has_dirty_io() take multiple bdi_writeback's into account Tejun Heo
2015-03-23 4:54 ` Tejun Heo
2015-03-23 4:54 ` [PATCH 32/48] writeback: don't issue wb_writeback_work if clean Tejun Heo
2015-03-23 4:54 ` Tejun Heo
2015-03-23 4:54 ` [PATCH 33/48] writeback: make bdi->min/max_ratio handling cgroup writeback aware Tejun Heo
2015-03-23 4:54 ` Tejun Heo
2015-03-23 4:54 ` [PATCH 34/48] writeback: implement bdi_for_each_wb() Tejun Heo
2015-03-23 4:54 ` Tejun Heo
2015-03-23 4:54 ` [PATCH 35/48] writeback: remove bdi_start_writeback() Tejun Heo
2015-03-23 4:54 ` Tejun Heo
2015-03-23 4:54 ` [PATCH 36/48] writeback: make laptop_mode_timer_fn() handle multiple bdi_writeback's Tejun Heo
2015-03-23 4:54 ` Tejun Heo
2015-03-23 4:54 ` [PATCH 37/48] writeback: make writeback_in_progress() take bdi_writeback instead of backing_dev_info Tejun Heo
2015-03-23 4:54 ` Tejun Heo
2015-03-23 4:54 ` [PATCH 38/48] writeback: make bdi_start_background_writeback() " Tejun Heo
2015-03-23 4:54 ` Tejun Heo
2015-03-23 4:54 ` [PATCH 39/48] writeback: make wakeup_flusher_threads() handle multiple bdi_writeback's Tejun Heo
2015-03-23 4:54 ` Tejun Heo
2015-03-23 4:54 ` [PATCH 40/48] writeback: add wb_writeback_work->auto_free Tejun Heo
2015-03-23 4:54 ` Tejun Heo
2015-03-23 4:54 ` [PATCH 41/48] writeback: implement bdi_wait_for_completion() Tejun Heo
2015-03-23 4:54 ` Tejun Heo
2015-03-23 4:54 ` [PATCH 42/48] writeback: implement wb_wait_for_single_work() Tejun Heo
2015-03-23 4:54 ` Tejun Heo
2015-03-23 4:54 ` [PATCH 43/48] writeback: restructure try_writeback_inodes_sb[_nr]() Tejun Heo
2015-03-23 4:54 ` Tejun Heo
2015-03-23 4:54 ` Tejun Heo
2015-03-23 4:54 ` [PATCH 44/48] writeback: make writeback initiation functions handle multiple bdi_writeback's Tejun Heo
2015-03-23 4:54 ` Tejun Heo
2015-03-23 4:54 ` [PATCH 45/48] writeback: dirty inodes against their matching cgroup bdi_writeback's Tejun Heo
2015-03-23 4:54 ` Tejun Heo
2015-03-23 4:54 ` [PATCH 46/48] buffer, writeback: make __block_write_full_page() honor cgroup writeback Tejun Heo
2015-03-23 4:54 ` Tejun Heo
2015-03-23 4:54 ` [PATCH 47/48] mpage: make __mpage_writepage() " Tejun Heo
2015-03-23 4:54 ` Tejun Heo
2015-03-23 4:54 ` [PATCH 48/48] ext2: enable cgroup writeback support Tejun Heo
2015-03-23 4:54 ` Tejun Heo
2015-03-25 15:40 ` [PATCHSET 1/3 v2 block/for-4.1/core] writeback: " Vivek Goyal
2015-03-25 15:40 ` Vivek Goyal
2015-03-25 15:40 ` Vivek Goyal
2015-03-25 16:01 ` Tejun Heo
2015-03-25 16:01 ` Tejun Heo
2015-03-25 16:01 ` Tejun Heo
2015-03-31 15:26 ` Tejun Heo
2015-03-31 15:26 ` Tejun Heo
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