Commit 3a8e9ac8 authored by Tejun Heo's avatar Tejun Heo Committed by Jens Axboe
Browse files

writeback: add tracepoints for cgroup foreign writebacks 



cgroup foreign inode handling has quite a bit of heuristics and
internal states which sometimes makes it difficult to understand
what's going on.  Add tracepoints to improve visibility.

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent e916ad29

fs/fs-writeback.c

+5 −0
Original line number Diff line number Diff line
@@ -389,6 +389,8 @@ static void inode_switch_wbs_work_fn(struct work_struct *work) 
	if (unlikely(inode->i_state & I_FREEING))

		goto skip_switch;



	trace_inode_switch_wbs(inode, old_wb, new_wb);



	/*

	 * Count and transfer stats.  Note that PAGECACHE_TAG_DIRTY points

	 * to possibly dirty pages while PAGECACHE_TAG_WRITEBACK points to
@@ -673,6 +675,9 @@ void wbc_detach_inode(struct writeback_control *wbc) 
		if (wbc->wb_id != max_id)

			history |= (1U << slots) - 1;



		if (history)

			trace_inode_foreign_history(inode, wbc, history);



		/*

		 * Switch if the current wb isn't the consistent winner.

		 * If there are multiple closely competing dirtiers, the

include/trace/events/writeback.h

+123 −0
Original line number Diff line number Diff line
@@ -176,6 +176,129 @@ static inline unsigned int __trace_wbc_assign_cgroup(struct writeback_control *w 
#endif	/* CONFIG_CGROUP_WRITEBACK */

#endif	/* CREATE_TRACE_POINTS */



#ifdef CONFIG_CGROUP_WRITEBACK

TRACE_EVENT(inode_foreign_history,



	TP_PROTO(struct inode *inode, struct writeback_control *wbc,

		 unsigned int history),



	TP_ARGS(inode, wbc, history),



	TP_STRUCT__entry(

		__array(char,		name, 32)

		__field(unsigned long,	ino)

		__field(unsigned int,	cgroup_ino)

		__field(unsigned int,	history)

	),



	TP_fast_assign(

		strncpy(__entry->name, dev_name(inode_to_bdi(inode)->dev), 32);

		__entry->ino		= inode->i_ino;

		__entry->cgroup_ino	= __trace_wbc_assign_cgroup(wbc);

		__entry->history	= history;

	),



	TP_printk("bdi %s: ino=%lu cgroup_ino=%u history=0x%x",

		__entry->name,

		__entry->ino,

		__entry->cgroup_ino,

		__entry->history

	)

);



TRACE_EVENT(inode_switch_wbs,



	TP_PROTO(struct inode *inode, struct bdi_writeback *old_wb,

		 struct bdi_writeback *new_wb),



	TP_ARGS(inode, old_wb, new_wb),



	TP_STRUCT__entry(

		__array(char,		name, 32)

		__field(unsigned long,	ino)

		__field(unsigned int,	old_cgroup_ino)

		__field(unsigned int,	new_cgroup_ino)

	),



	TP_fast_assign(

		strncpy(__entry->name,	dev_name(old_wb->bdi->dev), 32);

		__entry->ino		= inode->i_ino;

		__entry->old_cgroup_ino	= __trace_wb_assign_cgroup(old_wb);

		__entry->new_cgroup_ino	= __trace_wb_assign_cgroup(new_wb);

	),



	TP_printk("bdi %s: ino=%lu old_cgroup_ino=%u new_cgroup_ino=%u",

		__entry->name,

		__entry->ino,

		__entry->old_cgroup_ino,

		__entry->new_cgroup_ino

	)

);



TRACE_EVENT(track_foreign_dirty,



	TP_PROTO(struct page *page, struct bdi_writeback *wb),



	TP_ARGS(page, wb),



	TP_STRUCT__entry(

		__array(char,		name, 32)

		__field(u64,		bdi_id)

		__field(unsigned long,	ino)

		__field(unsigned int,	memcg_id)

		__field(unsigned int,	cgroup_ino)

		__field(unsigned int,	page_cgroup_ino)

	),



	TP_fast_assign(

		strncpy(__entry->name,	dev_name(wb->bdi->dev), 32);

		__entry->bdi_id		= wb->bdi->id;

		__entry->ino		= page->mapping->host->i_ino;

		__entry->memcg_id	= wb->memcg_css->id;

		__entry->cgroup_ino	= __trace_wb_assign_cgroup(wb);

		__entry->page_cgroup_ino = page->mem_cgroup->css.cgroup->kn->id.ino;

	),



	TP_printk("bdi %s[%llu]: ino=%lu memcg_id=%u cgroup_ino=%u page_cgroup_ino=%u",

		__entry->name,

		__entry->bdi_id,

		__entry->ino,

		__entry->memcg_id,

		__entry->cgroup_ino,

		__entry->page_cgroup_ino

	)

);



TRACE_EVENT(flush_foreign,



	TP_PROTO(struct bdi_writeback *wb, unsigned int frn_bdi_id,

		 unsigned int frn_memcg_id),



	TP_ARGS(wb, frn_bdi_id, frn_memcg_id),



	TP_STRUCT__entry(

		__array(char,		name, 32)

		__field(unsigned int,	cgroup_ino)

		__field(unsigned int,	frn_bdi_id)

		__field(unsigned int,	frn_memcg_id)

	),



	TP_fast_assign(

		strncpy(__entry->name,	dev_name(wb->bdi->dev), 32);

		__entry->cgroup_ino	= __trace_wb_assign_cgroup(wb);

		__entry->frn_bdi_id	= frn_bdi_id;

		__entry->frn_memcg_id	= frn_memcg_id;

	),



	TP_printk("bdi %s: cgroup_ino=%u frn_bdi_id=%u frn_memcg_id=%u",

		__entry->name,

		__entry->cgroup_ino,

		__entry->frn_bdi_id,

		__entry->frn_memcg_id

	)

);

#endif



DECLARE_EVENT_CLASS(writeback_write_inode_template,



	TP_PROTO(struct inode *inode, struct writeback_control *wbc),

mm/memcontrol.c

+5 −0
Original line number Diff line number Diff line
@@ -4066,6 +4066,8 @@ static int mem_cgroup_oom_control_write(struct cgroup_subsys_state *css, 


#ifdef CONFIG_CGROUP_WRITEBACK



#include <trace/events/writeback.h>



static int memcg_wb_domain_init(struct mem_cgroup *memcg, gfp_t gfp)

{

	return wb_domain_init(&memcg->cgwb_domain, gfp);
@@ -4203,6 +4205,8 @@ void mem_cgroup_track_foreign_dirty_slowpath(struct page *page, 
	int oldest = -1;

	int i;



	trace_track_foreign_dirty(page, wb);



	/*

	 * Pick the slot to use.  If there is already a slot for @wb, keep

	 * using it.  If not replace the oldest one which isn't being
@@ -4263,6 +4267,7 @@ void mem_cgroup_flush_foreign(struct bdi_writeback *wb) 
		if (time_after64(frn->at, now - intv) &&

		    atomic_read(&frn->done.cnt) == 1) {

			frn->at = 0;

			trace_flush_foreign(wb, frn->bdi_id, frn->memcg_id);

			cgroup_writeback_by_id(frn->bdi_id, frn->memcg_id, 0,

					       WB_REASON_FOREIGN_FLUSH,

					       &frn->done);