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Message-Id: <20211110114721.133808-1-alexs@kernel.org>
Date: Wed, 10 Nov 2021 19:47:21 +0800
From: alexs@...nel.org
To: unlisted-recipients:; (no To-header on input)
Cc: Alex Shi <alexs@...nel.org>, SeongJae Park <sj@...nel.org>,
Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
linux-kernel@...r.kernel.org
Subject: [RFC PATCH] mm/damon: remove damon_lock
From: Alex Shi <alexs@...nel.org>
Variable nr_running_ctxs guards by damon_lock, but a lock for a int
variable seems a bit heavy, a atomic_t is enough.
Signed-off-by: Alex Shi <alexs@...nel.org>
Cc: SeongJae Park <sj@...nel.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: linux-mm@...ck.org
Cc: linux-kernel@...r.kernel.org
---
include/linux/damon.h | 1 -
mm/damon/core.c | 31 +++++--------------------------
mm/damon/dbgfs.c | 8 +++++---
3 files changed, 10 insertions(+), 30 deletions(-)
diff --git a/include/linux/damon.h b/include/linux/damon.h
index b4d4be3cc987..e5dcc6336ef2 100644
--- a/include/linux/damon.h
+++ b/include/linux/damon.h
@@ -453,7 +453,6 @@ int damon_set_attrs(struct damon_ctx *ctx, unsigned long sample_int,
unsigned long min_nr_reg, unsigned long max_nr_reg);
int damon_set_schemes(struct damon_ctx *ctx,
struct damos **schemes, ssize_t nr_schemes);
-int damon_nr_running_ctxs(void);
int damon_start(struct damon_ctx **ctxs, int nr_ctxs);
int damon_stop(struct damon_ctx **ctxs, int nr_ctxs);
diff --git a/mm/damon/core.c b/mm/damon/core.c
index c381b3c525d0..e821e36d5c10 100644
--- a/mm/damon/core.c
+++ b/mm/damon/core.c
@@ -26,8 +26,7 @@
/* Get a random number in [l, r) */
#define damon_rand(l, r) (l + prandom_u32_max(r - l))
-static DEFINE_MUTEX(damon_lock);
-static int nr_running_ctxs;
+atomic_t nr_running_ctxs;
/*
* Construct a damon_region struct
@@ -356,20 +355,6 @@ int damon_set_schemes(struct damon_ctx *ctx, struct damos **schemes,
return 0;
}
-/**
- * damon_nr_running_ctxs() - Return number of currently running contexts.
- */
-int damon_nr_running_ctxs(void)
-{
- int nr_ctxs;
-
- mutex_lock(&damon_lock);
- nr_ctxs = nr_running_ctxs;
- mutex_unlock(&damon_lock);
-
- return nr_ctxs;
-}
-
/* Returns the size upper limit for each monitoring region */
static unsigned long damon_region_sz_limit(struct damon_ctx *ctx)
{
@@ -408,7 +393,7 @@ static int __damon_start(struct damon_ctx *ctx)
if (!ctx->kdamond) {
err = 0;
ctx->kdamond = kthread_run(kdamond_fn, ctx, "kdamond.%d",
- nr_running_ctxs);
+ atomic_read(&nr_running_ctxs));
if (IS_ERR(ctx->kdamond)) {
err = PTR_ERR(ctx->kdamond);
ctx->kdamond = NULL;
@@ -437,19 +422,15 @@ int damon_start(struct damon_ctx **ctxs, int nr_ctxs)
int i;
int err = 0;
- mutex_lock(&damon_lock);
- if (nr_running_ctxs) {
- mutex_unlock(&damon_lock);
+ if (atomic_read(&nr_running_ctxs))
return -EBUSY;
- }
for (i = 0; i < nr_ctxs; i++) {
err = __damon_start(ctxs[i]);
if (err)
break;
- nr_running_ctxs++;
+ atomic_inc(&nr_running_ctxs);
}
- mutex_unlock(&damon_lock);
return err;
}
@@ -1078,9 +1059,7 @@ static int kdamond_fn(void *data)
ctx->kdamond = NULL;
mutex_unlock(&ctx->kdamond_lock);
- mutex_lock(&damon_lock);
- nr_running_ctxs--;
- mutex_unlock(&damon_lock);
+ atomic_dec(&nr_running_ctxs);
return 0;
}
diff --git a/mm/damon/dbgfs.c b/mm/damon/dbgfs.c
index eccc14b34901..7182a46f6a2a 100644
--- a/mm/damon/dbgfs.c
+++ b/mm/damon/dbgfs.c
@@ -20,6 +20,8 @@ static int dbgfs_nr_ctxs;
static struct dentry **dbgfs_dirs;
static DEFINE_MUTEX(damon_dbgfs_lock);
+extern atomic_t nr_running_ctxs;
+
/*
* Returns non-empty string on success, negative error code otherwise.
*/
@@ -688,7 +690,7 @@ static int dbgfs_mk_context(char *name)
struct dentry *root, **new_dirs, *new_dir;
struct damon_ctx **new_ctxs, *new_ctx;
- if (damon_nr_running_ctxs())
+ if (atomic_read(&nr_running_ctxs))
return -EBUSY;
new_ctxs = krealloc(dbgfs_ctxs, sizeof(*dbgfs_ctxs) *
@@ -772,7 +774,7 @@ static int dbgfs_rm_context(char *name)
struct damon_ctx **new_ctxs;
int i, j;
- if (damon_nr_running_ctxs())
+ if (atomic_read(&nr_running_ctxs))
return -EBUSY;
root = dbgfs_dirs[0];
@@ -853,7 +855,7 @@ static ssize_t dbgfs_monitor_on_read(struct file *file,
char __user *buf, size_t count, loff_t *ppos)
{
char monitor_on_buf[5];
- bool monitor_on = damon_nr_running_ctxs() != 0;
+ bool monitor_on = atomic_read(&nr_running_ctxs) != 0;
int len;
len = scnprintf(monitor_on_buf, 5, monitor_on ? "on\n" : "off\n");
--
2.25.1
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