Improve performance by multithreading the work to preserve and restore
shmem pages.
Add 'pkram_max_threads=' kernel option to specify the maximum number
of threads to use to preserve or restore the pages of a shmem file.
The default is 16.
When preserving pages each thread saves chunks of a file to a pkram_obj
until no more no more chunks are available.
When restoring pages each thread loads pages using a copy of a
pkram_stream initialized by pkram_prepare_load_obj(). Under the hood
each thread ends up fetching and operating on pkram_link pages.
Signed-off-by: Anthony Yznaga <anthony.yznaga@xxxxxxxxxx>
---
include/linux/pkram.h | 2 +
mm/shmem_pkram.c | 101 +++++++++++++++++++++++++++++++++++++++++++++++++-
2 files changed, 101 insertions(+), 2 deletions(-)
diff --git a/include/linux/pkram.h b/include/linux/pkram.h
index e71ccb91d6a6..bf2e138b044e 100644
--- a/include/linux/pkram.h
+++ b/include/linux/pkram.h
@@ -13,6 +13,8 @@ struct pkram_stream {
struct pkram_node *node;
struct pkram_obj *obj;
+ int error;
+
struct pkram_link *link; /* current link */
unsigned int entry_idx; /* next entry in link */
diff --git a/mm/shmem_pkram.c b/mm/shmem_pkram.c
index 2f4d0bdf3e05..4992b6c3e54e 100644
--- a/mm/shmem_pkram.c
+++ b/mm/shmem_pkram.c
@@ -126,6 +126,16 @@ static int save_file_content_range(struct address_space *mapping,
return err;
}
+/* Completion tracking for do_save_file_content_thr() threads */
+static atomic_t pkram_save_n_undone;
+static DECLARE_COMPLETION(pkram_save_all_done_comp);
+
+static inline void pkram_save_report_one_done(void)
+{
+ if (atomic_dec_and_test(&pkram_save_n_undone))
+ complete(&pkram_save_all_done_comp);
+}
+
static int do_save_file_content(struct pkram_stream *ps)
{
int ret;
@@ -142,11 +152,55 @@ static int do_save_file_content(struct pkram_stream *ps)
return ret;
}
+static int do_save_file_content_thr(void *data)
+{
+ struct pkram_stream *ps = data;
+ struct pkram_stream pslocal = *ps;
+ int ret;
+
+ ret = do_save_file_content(&pslocal);
+ if (ret && !ps->error)
+ ps->error = ret;
+
+ pkram_save_report_one_done();
+ return 0;
+}
+#define PKRAM_DEFAULT_MAX_THREADS 16
+
+static int pkram_max_threads = PKRAM_DEFAULT_MAX_THREADS;
+
+static int __init set_pkram_max_threads(char *str)
+{
+ unsigned int val;
+
+ if (kstrtouint(str, 0, &val))
+ return 1;
+
+ pkram_max_threads = val;
+
+ return 1;
+}
+__setup("pkram_max_threads=", set_pkram_max_threads);
+
static int save_file_content(struct pkram_stream *ps)
{
+ unsigned int thr, nr_threads;
+
+ nr_threads = num_online_cpus() - 1;
+ nr_threads = clamp_val(pkram_max_threads, 1, nr_threads);
+
ps->max_idx = DIV_ROUND_UP(i_size_read(ps->mapping->host), PAGE_SIZE);
- return do_save_file_content(ps);
+ if (nr_threads == 1)
+ return do_save_file_content(ps);
+
+ atomic_set(&pkram_save_n_undone, nr_threads);
+ for (thr = 0; thr < nr_threads; thr++)
+ kthread_run(do_save_file_content_thr, ps, "pkram_save%d", thr);
+
+ wait_for_completion(&pkram_save_all_done_comp);
+
+ return ps->error;
}
static int save_file(struct dentry *dentry, struct pkram_stream *ps)
@@ -248,7 +302,17 @@ int shmem_save_pkram(struct super_block *sb)
return err;
}
-static int load_file_content(struct pkram_stream *ps)
+/* Completion tracking for do_load_file_content_thr() threads */
+static atomic_t pkram_load_n_undone;
+static DECLARE_COMPLETION(pkram_load_all_done_comp);
+
+static inline void pkram_load_report_one_done(void)
+{
+ if (atomic_dec_and_test(&pkram_load_n_undone))
+ complete(&pkram_load_all_done_comp);
+}
+
+static int do_load_file_content(struct pkram_stream *ps)
{
unsigned long index;
struct page *page;
@@ -266,6 +330,39 @@ static int load_file_content(struct pkram_stream *ps)
return err;
}
+static int do_load_file_content_thr(void *data)
+{
+ struct pkram_stream *ps = data;
+ struct pkram_stream pslocal = *ps;
+ int ret;
+
+ ret = do_load_file_content(&pslocal);
+ if (ret && !ps->error)
+ ps->error = ret;
+
+ pkram_load_report_one_done();
+ return 0;
+}
+
+static int load_file_content(struct pkram_stream *ps)
+{
+ unsigned int thr, nr_threads;
+
+ nr_threads = num_online_cpus() - 1;
+ nr_threads = clamp_val(pkram_max_threads, 1, nr_threads);
+
+ if (nr_threads == 1)
+ return do_load_file_content(ps);
+
+ atomic_set(&pkram_load_n_undone, nr_threads);
+ for (thr = 0; thr < nr_threads; thr++)
+ kthread_run(do_load_file_content_thr, ps, "pkram_load%d", thr);
+
+ wait_for_completion(&pkram_load_all_done_comp);
+
+ return ps->error;
+}
+
static int load_file(struct dentry *parent, struct pkram_stream *ps,
char *buf, size_t bufsize)
{
--
2.13.3
