If wq_cpu_set is specified, adjust thread_pool_size to the number of
CPUs in the set plus 2 to avoid the case where the number of CPUs in the
set is less than the default thread_pool_size + 2, which might cause the
thread pool to be starved. The thread_pool=%u mount option overrides
this adjusting behavior.
Signed-off-by: Ammar Faizi <ammarfaizi2@xxxxxxxxxxx>
---
fs/btrfs/super.c | 38 ++++++++++++++++++++++++++++++++++++++
1 file changed, 38 insertions(+)
diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index 3e061ec977b014d1..34b7c5810d34d624 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -317,6 +317,32 @@ static int parse_wq_cpu_set(struct btrfs_fs_info *info, const char *mask_str)
return 0;
}
+static void adjust_default_thread_pool_size(struct btrfs_fs_info *info)
+{
+ unsigned long old_thread_pool_size;
+ unsigned long new_thread_pool_size;
+ unsigned long total_usable_cpu = 0;
+ unsigned long cpu;
+
+ if (!btrfs_test_opt(info, WQ_CPU_SET))
+ return;
+
+ for_each_online_cpu(cpu) {
+ if (cpumask_test_cpu(cpu, info->wq_cpu_set->mask))
+ total_usable_cpu++;
+ }
+
+ old_thread_pool_size = info->thread_pool_size;
+ new_thread_pool_size = min_t(unsigned long, total_usable_cpu + 2, 8);
+
+ if (old_thread_pool_size == new_thread_pool_size)
+ return;
+
+ info->thread_pool_size = new_thread_pool_size;
+ btrfs_info(info, "adjusting thread_pool_size to %lu due to wq_cpu_set (you can override this with thread_pool=%%u option)",
+ new_thread_pool_size);
+}
+
/*
* Regular mount options parser. Everything that is needed only when
* reading in a new superblock is parsed here.
@@ -336,6 +362,7 @@ int btrfs_parse_options(struct btrfs_fs_info *info, char *options,
bool saved_compress_force;
int no_compress = 0;
const bool remounting = test_bit(BTRFS_FS_STATE_REMOUNTING, &info->fs_state);
+ bool has_thread_pool_opt = false;
if (btrfs_fs_compat_ro(info, FREE_SPACE_TREE))
btrfs_set_opt(info->mount_opt, FREE_SPACE_TREE);
@@ -543,6 +570,7 @@ int btrfs_parse_options(struct btrfs_fs_info *info, char *options,
goto out;
}
info->thread_pool_size = intarg;
+ has_thread_pool_opt = true;
break;
case Opt_max_inline:
num = match_strdup(&args[0]);
@@ -854,6 +882,16 @@ int btrfs_parse_options(struct btrfs_fs_info *info, char *options,
}
if (!ret)
ret = btrfs_check_mountopts_zoned(info);
+
+ /*
+ * If wq_cpu_set is specified, adjust thread_pool_size to the number of
+ * CPUs in the set plus 2 to avoid the case where the number of CPUs in
+ * the set is less than the default thread_pool_size + 2, which might
+ * cause the thread pool to be starved. The thread_pool=%u mount option
+ * overrides this adjusting behavior.
+ */
+ if (!ret && !has_thread_pool_opt)
+ adjust_default_thread_pool_size(info);
if (!ret && !remounting) {
if (btrfs_test_opt(info, SPACE_CACHE))
btrfs_info(info, "disk space caching is enabled");
--
Ammar Faizi
