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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: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Tejun Heo 2019-08-29 15:47:19 -07:00 committed by Jens Axboe
parent e916ad29d9
commit 3a8e9ac89e
3 changed files with 133 additions and 0 deletions
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5
fs/fs-writeback.c
View File

@ -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

123
include/trace/events/writeback.h
View File

@ -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),

5
mm/memcontrol.c
View File

@ -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);