Re: [PATCH] mmc:mmc-hsq:use fifo to dispatch mmc_request
From: Michael Wu
Date: Sun Nov 27 2022 - 22:56:04 EST
On 11/24/2022 10:56 AM, Wenchao Chen wrote:
On Mon, Nov 21, 2022 at 2:19 PM Michael Wu <michael@xxxxxxxxxxxxxxxxx> wrote:
On 11/18/2022 7:43 PM, Wenchao Chen wrote:
On Fri, Nov 18, 2022 at 1:52 PM Michael Wu <michael@xxxxxxxxxxxxxxxxx> wrote:
Current next_tag selection will cause a large delay in some requests and
destroy the scheduling results of the block scheduling layer. Because the
issued mrq tags cannot ensure that each time is sequential, especially when
the IO load is heavy. In the fio performance test, we found that 4k random
read data was sent to mmc_hsq to start calling request_atomic It takes
nearly 200ms to process the request, while mmc_hsq has processed thousands
of other requests. So we use fifo here to ensure the first in, first out
feature of the request and avoid adding additional delay to the request.
Hi Michael
Is the test device an eMMC?
Could you share the fio test command if you want?
Can you provide more logs?
Hi Wenchao,
Yes, the tested device is emmc.
The test command we used is `./fio -name=Rand_Read_IOPS_Test
-group_reporting -rw=random -bs=4K -numjobs=8 -directory=/data/data
-size=1G -io_size=64M -nrfiles=1 -direct=1 -thread && rm
/data/Rand_Read_IOPS_Test *`, which replaces the io performance random
read performance test of androidbench, and the file size is set to 1G, 8
thread test configuration. Where /data uses f2fs and /data/data is a
file encrypted path.
After enabling the hsq configuration, we can clearly see from below fio
test log that the minimum value of random reading is 3175 iops and the
maximum value is 8554iops, and the maximum delay of io completion is
about 200ms.
```
clat percentiles (usec):
| 1.00th=[ 498], 5.00th=[ 865], 10.00th=[ 963], 20.00th=[
1045],
| 30.00th=[ 1090], 40.00th=[ 1139], 50.00th=[ 1172], 60.00th=[
1221],
| 70.00th=[ 1254], 80.00th=[ 1319], 90.00th=[ 1401], 95.00th=[
1614],
| 99.00th=[ 2769], 99.50th=[ 3589], 99.90th=[ 31589], 99.95th=[
66323],
| 99.99th=[200279]
bw ( KiB/s): min=12705, max=34225, per=100.00%, avg=23931.79,
stdev=497.40, samples=345
iops : min= 3175, max= 8554, avg=5981.67, stdev=124.38,
samples=345
```
```
clat percentiles (usec):
| 1.00th=[ 799], 5.00th=[ 938], 10.00th=[ 963], 20.00th=[ 979],
| 30.00th=[ 996], 40.00th=[ 1004], 50.00th=[ 1020], 60.00th=[ 1045],
| 70.00th=[ 1074], 80.00th=[ 1106], 90.00th=[ 1172], 95.00th=[ 1237],
| 99.00th=[ 1450], 99.50th=[ 1516], 99.90th=[ 1762], 99.95th=[ 2180],
| 99.99th=[ 9503]
bw ( KiB/s): min=29200, max=30944, per=100.00%, avg=30178.91,
stdev=53.45, samples=272
iops : min= 7300, max= 7736, avg=7544.62, stdev=13.38,
samples=272
```
When NOT enabling hsq, the minimum value of random reading is 7300 iops
and the maximum value is 7736 iops, and the maximum delay of io is only
9 ms. Finally, we added debug to the mmc driver. The reason for locating
the 200ms delay of hsq is due to the next tag selection of hsq.
Thank you very much for your Log. This patch can reduce latency, but I
have some questions:
1. FIO -rw does not have random, but it does have randread. Do you use
randread? In addition, "IO_SIZE=64M" means only 64M data is tested?
Refer to FIO:
https://fio.readthedocs.io/en/latest/fio_doc.html?highlight=io_size#cmdoption-arg-io-size
Hi Wenchao,
Yes, I used "randread". (Sorry, I wrote the parameter "random"
incorrectly.) The reason why I used "io_size=64M" is that I found the
performance of hsq was degraded when using the AndroBench for testing on
android13. Therefore, fio is used to simulate the AndroBench for
debugging. The AndroBench is configured with 8 threads while 1G files
per thread, and only 64M data for random read testing（This item is not
configurable）.
2. The style of "tag_tail" should remain the same as that of
"next_tag". Would "tail_tag" be better?
Thank you for your suggestion. I'll modify 'tag_tail' as 'tail_tag'.
3. It is better to provide a comparison of sequential read, sequential
write and random writeHere is the performance data tested by AndroBench:
-------------------------------------------------------------------------
io performance data from AndroBench (filesize=1G, 8 threads)
-------------------------------------------------------------------------
mmc configure | original hsq | without hsq | hsq with this patch
-------------------------------------------------------------------------
Sequential write 58.23 MB/s 51.35 MB/s 56.15 MB/s
Sequential read 138.24 MB/s 143.65 MB/s 146.4 MB/s
random write 2900.11 iops 1887.13 iops 2982.02 iops
random read 4764.45 iops 5485.19 iops 6786.42 iops
Here's a preview of patch-v2. If it's OK, I'll submit it soon. Thank you.
--
mmc:mmc-hsq:use fifo to dispatch mmc_request
Current next_tag selection will cause a large delay in some requests and
destroy the scheduling results of the block scheduling layer. Because
the issued mrq tags cannot ensure that each time is sequential,
especially when the IO load is heavy. In the fio performance test, we
found that 4k random read data was sent to mmc_hsq to start calling
request_atomic It takes nearly 200ms to process the request, while
mmc_hsq has processed thousands of other requests. So we use fifo here
to ensure the first in, first out feature of the request and avoid
adding additional delay to the request.
diff --git a/drivers/mmc/host/mmc_hsq.c b/drivers/mmc/host/mmc_hsq.c
index 9d35453e7371..424dc7b07858 100644
--- a/drivers/mmc/host/mmc_hsq.c
+++ b/drivers/mmc/host/mmc_hsq.c
@@ -13,9 +13,6 @@
#include "mmc_hsq.h"
-#define HSQ_NUM_SLOTS 64
-#define HSQ_INVALID_TAG HSQ_NUM_SLOTS
-
static void mmc_hsq_retry_handler(struct work_struct *work)
{
struct mmc_hsq *hsq = container_of(work, struct mmc_hsq, retry_work);
@@ -73,7 +70,6 @@ static void mmc_hsq_pump_requests(struct mmc_hsq *hsq)
static void mmc_hsq_update_next_tag(struct mmc_hsq *hsq, int remains)
{
- struct hsq_slot *slot;
int tag;
/*
@@ -82,29 +78,12 @@ static void mmc_hsq_update_next_tag(struct mmc_hsq
*hsq, int remains)
*/
if (!remains) {
hsq->next_tag = HSQ_INVALID_TAG;
+ hsq->tail_tag = HSQ_INVALID_TAG;
return;
}
- /*
- * Increasing the next tag and check if the corresponding request is
- * available, if yes, then we found a candidate request.
- */
- if (++hsq->next_tag != HSQ_INVALID_TAG) {
- slot = &hsq->slot[hsq->next_tag];
- if (slot->mrq)
- return;
- }
-
- /* Othersie we should iterate all slots to find a available tag. */
- for (tag = 0; tag < HSQ_NUM_SLOTS; tag++) {
- slot = &hsq->slot[tag];
- if (slot->mrq)
- break;
- }
-
- if (tag == HSQ_NUM_SLOTS)
- tag = HSQ_INVALID_TAG;
-
+ tag = hsq->tag_slot[hsq->next_tag];
+ hsq->tag_slot[hsq->next_tag] = HSQ_INVALID_TAG;
hsq->next_tag = tag;
}
@@ -233,8 +212,14 @@ static int mmc_hsq_request(struct mmc_host *mmc,
struct mmc_request *mrq)
* Set the next tag as current request tag if no available
* next tag.
*/
- if (hsq->next_tag == HSQ_INVALID_TAG)
+ if (hsq->next_tag == HSQ_INVALID_TAG) {
hsq->next_tag = tag;
+ hsq->tail_tag = tag;
+ hsq->tag_slot[hsq->tail_tag] = HSQ_INVALID_TAG;
+ } else {
+ hsq->tag_slot[hsq->tail_tag] = tag;
+ hsq->tail_tag = tag;
+ }
hsq->qcnt++;
@@ -339,8 +324,10 @@ static const struct mmc_cqe_ops mmc_hsq_ops = {
int mmc_hsq_init(struct mmc_hsq *hsq, struct mmc_host *mmc)
{
+ int i;
hsq->num_slots = HSQ_NUM_SLOTS;
hsq->next_tag = HSQ_INVALID_TAG;
+ hsq->tail_tag = HSQ_INVALID_TAG;
hsq->slot = devm_kcalloc(mmc_dev(mmc), hsq->num_slots,
sizeof(struct hsq_slot), GFP_KERNEL);
@@ -351,6 +338,9 @@ int mmc_hsq_init(struct mmc_hsq *hsq, struct
mmc_host *mmc)
hsq->mmc->cqe_private = hsq;
mmc->cqe_ops = &mmc_hsq_ops;
+ for (i = 0; i < HSQ_NUM_SLOTS; i++)
+ hsq->tag_slot[i] = HSQ_INVALID_TAG;
+
INIT_WORK(&hsq->retry_work, mmc_hsq_retry_handler);
spin_lock_init(&hsq->lock);
init_waitqueue_head(&hsq->wait_queue);
diff --git a/drivers/mmc/host/mmc_hsq.h b/drivers/mmc/host/mmc_hsq.h
index ffdd9cd172c3..1808024fc6c5 100644
--- a/drivers/mmc/host/mmc_hsq.h
+++ b/drivers/mmc/host/mmc_hsq.h
@@ -2,6 +2,9 @@
#ifndef LINUX_MMC_HSQ_H
#define LINUX_MMC_HSQ_H
+#define HSQ_NUM_SLOTS 64
+#define HSQ_INVALID_TAG HSQ_NUM_SLOTS
+
struct hsq_slot {
struct mmc_request *mrq;
};
@@ -17,6 +20,8 @@ struct mmc_hsq {
int next_tag;
int num_slots;
int qcnt;
+ int tail_tag;
+ int tag_slot[HSQ_NUM_SLOTS];
bool enabled;
bool waiting_for_idle;
--
Regards,
Michael Wu