From: Manish Varma <varmam@google.com>
To: Alexander Viro <viro@zeniv.linux.org.uk>,
Thomas Gleixner <tglx@linutronix.de>
Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
kernel-team@android.com, Manish Varma <varmam@google.com>,
Kelly Rossmoyer <krossmo@google.com>
Subject: [PATCH v2] fs: Improve eventpoll logging to stop indicting timerfd
Date: Wed, 31 Mar 2021 19:16:45 -0700 [thread overview]
Message-ID: <20210401021645.2609047-1-varmam@google.com> (raw)
timerfd doesn't create any wakelocks, but eventpoll can. When it does,
it names them after the underlying file descriptor, and since all
timerfd file descriptors are named "[timerfd]" (which saves memory on
systems like desktops with potentially many timerfd instances), all
wakesources created as a result of using the eventpoll-on-timerfd idiom
are called... "[timerfd]".
However, it becomes impossible to tell which "[timerfd]" wakesource is
affliated with which process and hence troubleshooting is difficult.
This change addresses this problem by changing the way eventpoll
wakesources are named:
1) the top-level per-process eventpoll wakesource is now named "epoll:P"
(instead of just "eventpoll"), where P, is the PID of the creating
process.
2) individual per-underlying-filedescriptor eventpoll wakesources are
now named "epollitemN:P.F", where N is a unique ID token and P is PID
of the creating process and F is the name of the underlying file
descriptor.
All together that should be splitted up into a change to eventpoll and
timerfd (or other file descriptors).
Co-developed-by: Kelly Rossmoyer <krossmo@google.com>
Signed-off-by: Kelly Rossmoyer <krossmo@google.com>
Signed-off-by: Manish Varma <varmam@google.com>
---
fs/eventpoll.c | 13 +++++++++++--
1 file changed, 11 insertions(+), 2 deletions(-)
diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index 7df8c0fa462b..8d3369a02633 100644
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -297,6 +297,7 @@ static LIST_HEAD(tfile_check_list);
static long long_zero;
static long long_max = LONG_MAX;
+static atomic_t wakesource_create_id = ATOMIC_INIT(0);
struct ctl_table epoll_table[] = {
{
@@ -1451,15 +1452,23 @@ static int ep_create_wakeup_source(struct epitem *epi)
{
struct name_snapshot n;
struct wakeup_source *ws;
+ pid_t task_pid;
+ char buf[64];
+ int id;
+
+ task_pid = task_pid_nr(current);
if (!epi->ep->ws) {
- epi->ep->ws = wakeup_source_register(NULL, "eventpoll");
+ snprintf(buf, sizeof(buf), "epoll:%d", task_pid);
+ epi->ep->ws = wakeup_source_register(NULL, buf);
if (!epi->ep->ws)
return -ENOMEM;
}
+ id = atomic_inc_return(&wakesource_create_id);
take_dentry_name_snapshot(&n, epi->ffd.file->f_path.dentry);
- ws = wakeup_source_register(NULL, n.name.name);
+ snprintf(buf, sizeof(buf), "epollitem%d:%d.%s", id, task_pid, n.name.name);
+ ws = wakeup_source_register(NULL, buf);
release_dentry_name_snapshot(&n);
if (!ws)
--
2.31.0.291.g576ba9dcdaf-goog
next reply other threads:[~2021-04-01 2:17 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-01 2:16 Manish Varma [this message]
2021-04-01 2:28 ` [PATCH v2] fs: Improve eventpoll logging to stop indicting timerfd Al Viro
2021-04-01 23:57 ` Manish Varma
2021-04-01 6:44 ` kernel test robot
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