| Message ID | cover.1603938304.git.anand.jain@oracle.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c index d3023879bdf6..72ec633e9063 100644 --- a/fs/btrfs/volumes.c +++ b/fs/btrfs/volumes.c @@ -5665,6 +5665,12 @@ static int find_live_mirror(struct btrfs_fs_info *fs_info, fs_info->fs_devices->read_policy = BTRFS_READ_POLICY_PID; fallthrough; case BTRFS_READ_POLICY_PID: + /* + * Just to factor in the cost of calculating the avg wait using + * iostat for testing. + */ + btrfs_find_best_stripe(fs_info, map, first, num_stripes, log, + logsz); preferred_mirror = first + current->pid % num_stripes; scnprintf(log, logsz, "first %d num_stripe %d %s (%d) preferred %d",
Based on misc-next Depends on the following 3 patches in the mailing list [1] btrfs: add btrfs_strmatch helper btrfs: create read policy framework btrfs: create read policy sysfs attribute, pid [1] https://patchwork.kernel.org/project/linux-btrfs/list/?series=372217 v2: Fixes as per review comments, as in the individual patches. raid1 performance: pid latency [device] roundrobin ( 01) READ: bw=42.1MiB/s (44.2MB/s), 42.1MiB/s-42.1MiB/s (44.2MB/s-44.2MB/s), io=15.6GiB (16.8GB), run=379781-379781msec vdb 256242 sda 0 [pid] latency device roundrobin ( 00) READ: bw=40.7MiB/s (42.7MB/s), 40.7MiB/s-40.7MiB/s (42.7MB/s-42.7MB/s), io=15.6GiB (16.8GB), run=393199-393199msec vdb 128097 sda 128106 pid [latency] device roundrobin ( 00) READ: bw=41.7MiB/s (43.8MB/s), 41.7MiB/s-41.7MiB/s (43.8MB/s-43.8MB/s), io=15.6GiB (16.8GB), run=383274-383274msec vdb 256238 sda 0 pid latency device [roundrobin] ( 00) READ: bw=35.3MiB/s (36.0MB/s), 35.3MiB/s-35.3MiB/s (36.0MB/s-36.0MB/s), io=15.6GiB (16.8GB), run=453535-453535msec vdb 1149797 sda 1148975 ---------------------------------------------------- v1: Drop tracing patch Drop factoring inflight command Here below is the performance differences, when inflight is used, it pushed few commands to the other device, so losing the potential merges. Few C styles fixes. < logs removed > RFC: Patch 1-3 adds new read policy: latency. Patch 4 adds tracing function. Patch 5-6 were sent before they add read policy: device. Patch 7 adds new read policy: round-robin. I am sending this patchset to receive feedback, comments, and more test results. Few cleanups, optimization, and broader performance test are may be possible. This patchset does not alter the original default read_policy that is PID. This has been tested on VMs only, as my hardware based test host is currently down. This patchset adds read policies type latency, device, and round-robin. These policies are for the mirrored raid profiles such as raid1, raid1c3, raid1c4, and raid10 as they provide a choice to read from any one of the given devices or any one pair of devices for raid10 for a given block. Latency: Latency read policy routes the read IO based on the historical average wait time experienced by the read IOs on the individual device factored by 1/10 of inflight commands in the queue. I need to add a factor of 1/10 because for most of the block devices the queue depth is more than 1, and there can be commands in the queue even before the previous commands have completed. However, the factor 1/10 for the inflight commands is yet to be fine-tuned. Suggestions are welcome. Device: With the device read policy along with the read_preferred flag, you can set the device to be used for reading manually. Useful to test mirrors in a deterministic way and helps advance system administrations. Round-robin: When set picks the next device to read in the round-robin loop. To achieve this first we put the stripes in an array, sort it by devid and pick the next device. The test results from my VM with 2 devices of type sata and 2 devices of type virtio, are as below. Here below I have included a few scripts which were useful for testing. -------------------8<-------------------------------- $ cat readpolicyset #!/bin/bash : ${1?"arg1 <mnt> missing"} : ${2?"arg2 <pid|latency|device|roundrobin> missing"} mnt=$1 policy=$2 [ $policy == "device" ] && { : ${3?"arg3 <devid> missing"}; } devid=$3 uuid=$(btrfs fi show -m /btrfs | grep uuid | awk '{print $4}') p=/sys/fs/btrfs/$uuid/read_policy q=/sys/fs/btrfs/$uuid/devinfo [ $policy == "device" ] && { echo 1 > ${q}/$devid/read_preferred || exit $?; } echo $policy > $p exit $? -------------------8<-------------------------------- $ cat readpolicy #!/bin/bash : ${1?"arg1 <mnt> missing"} mnt=$1 uuid=$(btrfs fi show -m /btrfs | grep uuid | awk '{print $4}') p=/sys/fs/btrfs/$uuid/read_policy q=/sys/fs/btrfs/$uuid/devinfo policy=$(cat $p) echo -n "$policy ( " for i in $(find $q -type f -name read_preferred | xargs cat) do echo -n "$i" done echo ")" -------------------8<-------------------------------- $ cat readstat #!/bin/bash : ${1?"arg1 <mnt> is missing"} : ${2?"arg2 <cmd-to-run> is missing"} mnt=$1; shift mountpoint -q $mnt || { echo "ERROR: $mnt is not mounted"; exit 1; } declare -A devread for dev in $(btrfs filesystem show -m $mnt | grep devid |awk '{print $8}') do prefix=$(echo $dev | rev | cut -d"/" -f1 | rev) sysfs_path=$(find /sys | grep $prefix/stat$) devread[$sysfs_path]=$(cat $sysfs_path | awk '{print $1}') done "$@" | grep "READ: bw" echo echo for sysfs_path in ${!devread[@]} do dev=$(echo $sysfs_path | rev | cut -d"/" -f2 | rev) new=$(cat $sysfs_path | awk '{print $1}') old=${devread[$sysfs_path]} echo "$dev $((new - old))" done -------------------8<-------------------------------- $ cat fioread #!/bin/bash : ${1?"arg1 </mnt/file> is missing"} : ${2?"arg2 <1Gi|50Gi> is missing"} tf=$1 sz=$2 mnt=$(stat -c '%m' $tf) fio \ --filename=$tf \ --directory=$mnt \ --filesize=$sz \ --size=$sz \ --rw=randread \ --bs=64k \ --ioengine=libaio \ --direct=1 \ --numjobs=32 \ --group_reporting \ --thread \ --name iops-test-job -------------------8<-------------------------------- Here below are the performance results for raid1c4, raid10, and raid1. The workload is fio read 32 threads, 500m random reads. Fio is passed to the script readstat, which returns the number of read IOs per device sent during the fio. Few inferences: 1. In some cases as mine, PID is also associated with the stripe 0 being circulating among the devices at the chunk level before moving to the next device. So PID is not a bad option for such configurations. However, it is not a good choice if the devices are heterogeneous in terms of type, speed, and size. 2. Latency provides performance equal to PID on my test setup. But needs iostat be enabled. And there is a cost of calculating the avg wait time. (If you factor in the similar cost to PID using the test code [1] then latency's performance is better than PID. So that proves that read IO distribution as per latency is really working) 3. Round robin is worst (unless there is a bug in my patch). As the total number of new IOs issued was almost double compared to the PID and the latency read_policy, that's because I think there was a fewer number of merges due to constant switching of devices. 4. Device read_policy is quite useful in testing and advance sysadmin maintenance. When known how to use, this policy could help to avert too many csum errors in midest of peak production. Supporting fio logs are below. And readstat shows the number of read IOs issued to devices (excluding the merges). raid1c4 ------- pid: $ readpolicyset /btrfs pid && readpolicy /btrfs && dropcache && readstat /btrfs fioread /btrfs/largefile 500m [pid] latency device roundrobin ( 0000) READ: bw=87.0MiB/s (91.2MB/s), 87.0MiB/s-87.0MiB/s (91.2MB/s-91.2MB/s), io=15.6GiB (16.8GB), run=183884-183884msec vdb 64060 vdc 64053 sdb 64072 sda 64054 latency: (All devices are non-rotational, but sda and sdb are of type sata and vdb and vdc are of type virtio). $ readpolicyset /btrfs latency && readpolicy /btrfs && dropcache && readstat /btrfs fioread /btrfs/largefile 500m pid [latency] device roundrobin ( 0000) READ: bw=87.1MiB/s (91.3MB/s), 87.1MiB/s-87.1MiB/s (91.3MB/s-91.3MB/s), io=15.6GiB (16.8GB), run=183774-183774msec vdb 255844 vdc 559 sdb 0 sda 93 roundrobin: $ readpolicyset /btrfs roundrobin && readpolicy /btrfs && dropcache && readstat /btrfs fioread /btrfs/largefile 500m pid latency device [roundrobin] ( 0000) READ: bw=51.0MiB/s (54.5MB/s), 51.0MiB/s-51.0MiB/s (54.5MB/s-54.5MB/s), io=15.6GiB (16.8GB), run=307755-307755msec vdb 866859 vdc 866651 sdb 864139 sda 865533 raid10 ------ pid: $ readpolicyset /btrfs pid && readpolicy /btrfs && dropcache && readstat /btrfs fioread /btrfs/largefile 500m [pid] latency device roundrobin ( 0000) READ: bw=85.2MiB/s (89.3MB/s), 85.2MiB/s-85.2MiB/s (89.3MB/s-89.3MB/s), io=15.6GiB (16.8GB), run=187864-187864msec sdf 64053 sde 64036 sdd 64043 sdc 64038 latency: $ readpolicyset /btrfs latency && readpolicy /btrfs && dropcache && readstat /btrfs fioread /btrfs/largefile 500m pid [latency] device roundrobin ( 0000) READ: bw=85.4MiB/s (89.5MB/s), 85.4MiB/s-85.4MiB/s (89.5MB/s-89.5MB/s), io=15.6GiB (16.8GB), run=187370-187370msec sdf 117494 sde 10748 sdd 125247 sdc 2921 roundrobin: $ readpolicyset /btrfs roundrobin && readpolicy /btrfs && dropcache && readstat /btrfs fioread /btrfs/largefile 500m pid latency device [roundrobin] ( 0000) READ: bw=55.4MiB/s (58.1MB/s), 55.4MiB/s-55.4MiB/s (58.1MB/s-58.1MB/s), io=15.6GiB (16.8GB), run=288701-288701msec sdf 617593 sde 617381 sdd 618486 sdc 618633 raid1: $ readpolicyset /btrfs pid && readpolicy /btrfs && dropcache && readstat /btrfs fioread /btrfs/largefile 500m [pid] latency device roundrobin ( 00) READ: bw=78.8MiB/s (82.6MB/s), 78.8MiB/s-78.8MiB/s (82.6MB/s-82.6MB/s), io=15.6GiB (16.8GB), run=203158-203158msec sdb 128087 sda 128090 $ readpolicyset /btrfs latency && readpolicy /btrfs && dropcache && readstat /btrfs fioread /btrfs/largefile 500m pid [latency] device roundrobin ( 00) READ: bw=86.5MiB/s (90.7MB/s), 86.5MiB/s-86.5MiB/s (90.7MB/s-90.7MB/s), io=15.6GiB (16.8GB), run=185023-185023msec sdb 567 sda 255942 From the latency test results we know sda is providing low latency read IO. So set sda as read proffered device. $ readpolicyset /btrfs device 1 && readpolicy /btrfs && dropcache && readstat /btrfs fioread /btrfs/largefile 500m pid latency [device] roundrobin ( 10) READ: bw=88.2MiB/s (92.5MB/s), 88.2MiB/s-88.2MiB/s (92.5MB/s-92.5MB/s), io=15.6GiB (16.8GB), run=181374-181374msec sdb 0 sda 256191 $ readpolicyset /btrfs roundrobin && readpolicy /btrfs && dropcache && readstat /btrfs fioread /btrfs/largefile 500m pid latency device [roundrobin] ( 00) READ: bw=54.1MiB/s (56.7MB/s), 54.1MiB/s-54.1MiB/s (56.7MB/s-56.7MB/s), io=15.6GiB (16.8GB), run=295693-295693msec sdb 1252584 sda 1254258 Thanks, Anand ------------------ [1] Anand Jain (4): btrfs: add read_policy latency btrfs: introduce new device-state read_preferred btrfs: introduce new read_policy device btrfs: introduce new read_policy round-robin fs/btrfs/sysfs.c | 57 ++++++++++++++++++++++- fs/btrfs/volumes.c | 110 +++++++++++++++++++++++++++++++++++++++++++++ fs/btrfs/volumes.h | 5 +++ 3 files changed, 171 insertions(+), 1 deletion(-)