On 1/11/21 4:41 AM, Anand Jain wrote:
The read policy type latency routes the read IO based on the historical average wait-time experienced by the read IOs through the individual device. This patch obtains the historical read IO stats from the kernel block layer and calculates its average.Example usage: echo "latency" > /sys/fs/btrfs/$uuid/read_policy Signed-off-by: Anand Jain <anand.j...@oracle.com> --- v3: The block layer commit 0d02129e76ed (block: merge struct block_device and struct hd_struct) has changed the first argument in the function part_stat_read_all() in 5.11-rc1. So the compilation will fail. This patch fixes it. Commit log updated. v2: Use btrfs_debug_rl() instead of btrfs_info_rl() It is better we have this debug until we test this on at least few hardwares. Drop the unrelated changes. Update change log. v1: Drop part_stat_read_all instead use part_stat_read Drop inflight fs/btrfs/sysfs.c | 3 ++- fs/btrfs/volumes.c | 38 ++++++++++++++++++++++++++++++++++++++ fs/btrfs/volumes.h | 2 ++ 3 files changed, 42 insertions(+), 1 deletion(-) diff --git a/fs/btrfs/sysfs.c b/fs/btrfs/sysfs.c index 19b9fffa2c9c..96ca7bef6357 100644 --- a/fs/btrfs/sysfs.c +++ b/fs/btrfs/sysfs.c @@ -915,7 +915,8 @@ static bool strmatch(const char *buffer, const char *string) return false; }-static const char * const btrfs_read_policy_name[] = { "pid" };+/* Must follow the order as in enum btrfs_read_policy */ +static const char * const btrfs_read_policy_name[] = { "pid", "latency" };static ssize_t btrfs_read_policy_show(struct kobject *kobj,struct kobj_attribute *a, char *buf) diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c index f4037a6bd926..f7a0a83d2cd4 100644 --- a/fs/btrfs/volumes.c +++ b/fs/btrfs/volumes.c @@ -14,6 +14,7 @@ #include <linux/semaphore.h> #include <linux/uuid.h> #include <linux/list_sort.h> +#include <linux/part_stat.h> #include "misc.h" #include "ctree.h" #include "extent_map.h" @@ -5490,6 +5491,39 @@ int btrfs_is_parity_mirror(struct btrfs_fs_info *fs_info, u64 logical, u64 len) return ret; }+static int btrfs_find_best_stripe(struct btrfs_fs_info *fs_info,+ struct map_lookup *map, int first, + int num_stripe) +{ + u64 est_wait = 0; + int best_stripe = 0; + int index; + + for (index = first; index < first + num_stripe; index++) { + u64 read_wait; + u64 avg_wait = 0; + unsigned long read_ios; + struct btrfs_device *device = map->stripes[index].dev; + + read_wait = part_stat_read(device->bdev, nsecs[READ]); + read_ios = part_stat_read(device->bdev, ios[READ]); + + if (read_wait && read_ios && read_wait >= read_ios) + avg_wait = div_u64(read_wait, read_ios); + else + btrfs_debug_rl(device->fs_devices->fs_info,
You can just use fs_info here, you already have it. I'm not in love with doing this check every time, I'd rather cache the results somewhere. However if we're read-only I can't think of a mechanism we could piggy back on, RW we could just do it every transaction commit. Fix the fs_info thing and you can add
Reviewed-by: Josef Bacik <jo...@toxicpanda.com> Thanks, Josef
