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fscache: Add a tracepoint for cookie use/unuse

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Add a tracepoint to track fscache_use/unuse_cookie().

Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
cc: linux-cachefs@redhat.com
Link: https://lore.kernel.org/r/164021588628.640689.12942919367404043608.stgit@warthog.procyon.org.uk/ # v4
This commit is contained in:
David Howells 2021-12-06 15:54:04 +00:00
parent e0484344c0
commit e6435f1e02
2 changed files with 69 additions and 4 deletions
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29
fs/fscache/cookie.c
View file

@ -556,6 +556,7 @@ void __fscache_use_cookie(struct fscache_cookie *cookie, bool will_modify)
{
enum fscache_cookie_state state;
bool queue = false;
int n_active;
_enter("c=%08x", cookie->debug_id);
@ -565,7 +566,11 @@ void __fscache_use_cookie(struct fscache_cookie *cookie, bool will_modify)
spin_lock(&cookie->lock);
atomic_inc(&cookie->n_active);
n_active = atomic_inc_return(&cookie->n_active);
trace_fscache_active(cookie->debug_id, refcount_read(&cookie->ref),
n_active, atomic_read(&cookie->n_accesses),
will_modify ?
fscache_active_use_modify : fscache_active_use);
again:
state = fscache_cookie_state(cookie);
@ -638,13 +643,29 @@ static void fscache_unuse_cookie_locked(struct fscache_cookie *cookie)
void __fscache_unuse_cookie(struct fscache_cookie *cookie,
const void *aux_data, const loff_t *object_size)
{
unsigned int debug_id = cookie->debug_id;
unsigned int r = refcount_read(&cookie->ref);
unsigned int a = atomic_read(&cookie->n_accesses);
unsigned int c;
if (aux_data || object_size)
__fscache_update_cookie(cookie, aux_data, object_size);
if (atomic_dec_and_lock(&cookie->n_active, &cookie->lock)) {
fscache_unuse_cookie_locked(cookie);
spin_unlock(&cookie->lock);
/* Subtract 1 from counter unless that drops it to 0 (ie. it was 1) */
c = atomic_fetch_add_unless(&cookie->n_active, -1, 1);
if (c != 1) {
trace_fscache_active(debug_id, r, c - 1, a, fscache_active_unuse);
return;
}
spin_lock(&cookie->lock);
r = refcount_read(&cookie->ref);
a = atomic_read(&cookie->n_accesses);
c = atomic_dec_return(&cookie->n_active);
trace_fscache_active(debug_id, r, c, a, fscache_active_unuse);
if (c == 0)
fscache_unuse_cookie_locked(cookie);
spin_unlock(&cookie->lock);
}
EXPORT_SYMBOL(__fscache_unuse_cookie);

44
include/trace/events/fscache.h
View file

@ -71,6 +71,12 @@ enum fscache_cookie_trace {
fscache_cookie_see_work,
};
enum fscache_active_trace {
fscache_active_use,
fscache_active_use_modify,
fscache_active_unuse,
};
enum fscache_access_trace {
fscache_access_acquire_volume,
fscache_access_acquire_volume_end,
@ -146,6 +152,11 @@ enum fscache_access_trace {
EM(fscache_cookie_see_withdraw, "- x-wth") \
E_(fscache_cookie_see_work, "- work ")
#define fscache_active_traces \
EM(fscache_active_use, "USE ") \
EM(fscache_active_use_modify, "USE-m ") \
E_(fscache_active_unuse, "UNUSE ")
#define fscache_access_traces \
EM(fscache_access_acquire_volume, "BEGIN acq_vol") \
EM(fscache_access_acquire_volume_end, "END acq_vol") \
@ -264,6 +275,39 @@ TRACE_EVENT(fscache_cookie,
__entry->ref)
);
TRACE_EVENT(fscache_active,
TP_PROTO(unsigned int cookie_debug_id,
int ref,
int n_active,
int n_accesses,
enum fscache_active_trace why),
TP_ARGS(cookie_debug_id, ref, n_active, n_accesses, why),
TP_STRUCT__entry(
__field(unsigned int, cookie )
__field(int, ref )
__field(int, n_active )
__field(int, n_accesses )
__field(enum fscache_active_trace, why )
),
TP_fast_assign(
__entry->cookie = cookie_debug_id;
__entry->ref = ref;
__entry->n_active = n_active;
__entry->n_accesses = n_accesses;
__entry->why = why;
),
TP_printk("c=%08x %s r=%d a=%d c=%d",
__entry->cookie,
__print_symbolic(__entry->why, fscache_active_traces),
__entry->ref,
__entry->n_accesses,
__entry->n_active)
);
TRACE_EVENT(fscache_access_cache,
TP_PROTO(unsigned int cache_debug_id,
int ref,