On 11/22/24 1:55 PM, Sam Protsenko wrote:
On Fri, Nov 22, 2024 at 6:04 AM Christoph Hellwig <hch@xxxxxx> wrote:
On Thu, Nov 21, 2024 at 11:04:19PM -0600, Sam Protsenko wrote:
Hi Christoph,
This patch causes a regression on E850-96 board. Specifically, there are
two noticeable time lags when booting Debian rootfs:
What storage driver does this board use? Anything else interesting
about the setup?
It's an Exynos based board with eMMC, so it uses DW MMC driver, with
Exynos glue layer on top of it, so:
drivers/mmc/host/dw_mmc.c
drivers/mmc/host/dw_mmc-exynos.c
I'm using the regular ARM64 defconfig. Nothing fancy about this setup
neither, the device tree with eMMC definition (mmc_0) is here:
arch/arm64/boot/dts/exynos/exynos850-e850-96.dts
FWIW, I was able to narrow down the issue to dd_insert_request()
function. With this hack the freeze is gone:
8<-------------------------------------------------------------------->8
diff --git a/block/mq-deadline.c b/block/mq-deadline.c
index acdc28756d9d..83d272b66e71 100644
--- a/block/mq-deadline.c
+++ b/block/mq-deadline.c
@@ -676,7 +676,7 @@ static void dd_insert_request(struct blk_mq_hw_ctx
*hctx, struct request *rq,
struct request_queue *q = hctx->queue;
struct deadline_data *dd = q->elevator->elevator_data;
const enum dd_data_dir data_dir = rq_data_dir(rq);
- u16 ioprio = req_get_ioprio(rq);
+ u16 ioprio = 0; /* the same as old req->ioprio */
u8 ioprio_class = IOPRIO_PRIO_CLASS(ioprio);
struct dd_per_prio *per_prio;
enum dd_prio prio;
8<-------------------------------------------------------------------->8
Does it tell you anything about where the possible issue can be?
It seems like eMMC devices do not tolerate I/O prioritization. How about
disabling I/O prioritization for eMMC setups? Is the ioprio cgroup
controller perhaps activated by the user space software that is running
on this setup?
Thanks,
Bart.
