| Message ID | 1448982916-21485-1-git-send-email-ulf.hansson@linaro.org |
|---|---|
| State | New |
| Headers | show |
On 18 December 2015 at 04:05, Shawn Lin <shawn.lin@rock-chips.com> wrote: > On 2015/12/18 9:28, Jaehoon Chung wrote: >> >> Hi, >> >> On 12/18/2015 06:49 AM, Ulf Hansson wrote: >>> >>> On 17 December 2015 at 20:47, Alan Cooper <alcooperx@gmail.com> wrote: >>>> >>>> On Wed, Dec 16, 2015 at 4:07 AM, Ulf Hansson <ulf.hansson@linaro.org> >>>> wrote: >>>>> >>>>> To find the improved card detection times, I just used the kernel boot >>>>> log and checked the time stamps for when the cards get detected. I ran >>>>> the tests ~10 times and picked up some average values. >>>>> >>>>> To notice the improvement you need at least two cards to be inserted >>>>> during boot. Perhaps you have a platform with one eMMC and one SD card >>>>> slot, you can test. >>>> >>>> >>>> I tested the patch on one of our ARM bases SoC's. The SoC has an SD >>>> card slot on the first controller and an eMMC device on the second >>>> controller. I found ~100ms improvement on the time it took for the >>>> rootfs on the eMMC device to be ready for use. Interestingly, I did >>>> see the SD/eMMC order swap once in 20 tries. This is not an issue for >>>> us as we already have to use UUID for the eMMC rootfs in case an SD >>>> card is installed. >>>> > Hi Shawn, Thanks for helping out testing. > hi Ulf, > I'm interested in this patch since I also spent a little time optimzing > the boot time and sequence for my local branch based on kernel 3.1x. With > you patch, it seems, the tablet only achieves very small improvement for the > SD controller(less than 20ms). > > My test environment: > Kernel: 3.14 > Slot: 1 emmc(1st) + 1 SD card(2nd) + 1 sdio card(3rd) How much time you *gain* comparing to the original behaviour for each card, depends on the ->probe() order of your mmc hosts. I would guess that the host that holds the eMMC is the one being probed first, right? In general eMMC is quite fast to initialize, comparing to SD-cards and that's probably the reason to why you don't see that much improvements. Although, for your SDIO card you should see a greater improvement as this don't need to wait for your SD and eMMC to be initialized. > > I happen to run massive reboot test for my stable kernel branch this > weekend, so I will apply this patch to see if any problem occurs. :) > Great! As you haven't reported any problems, I suppose the tests went well!? Kind regards Uffe -- To unsubscribe from this list: send the line "unsubscribe linux-mmc" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c index 910aa25..f95d41f 100644 --- a/drivers/mmc/core/core.c +++ b/drivers/mmc/core/core.c @@ -55,7 +55,6 @@ */ #define MMC_BKOPS_MAX_TIMEOUT (4 * 60 * 1000) /* max time to wait in ms */ -static struct workqueue_struct *workqueue; static const unsigned freqs[] = { 400000, 300000, 200000, 100000 }; /* @@ -66,21 +65,16 @@ static const unsigned freqs[] = { 400000, 300000, 200000, 100000 }; bool use_spi_crc = 1; module_param(use_spi_crc, bool, 0); -/* - * Internal function. Schedule delayed work in the MMC work queue. - */ static int mmc_schedule_delayed_work(struct delayed_work *work, unsigned long delay) { - return queue_delayed_work(workqueue, work, delay); -} - -/* - * Internal function. Flush all scheduled work from the MMC work queue. - */ -static void mmc_flush_scheduled_work(void) -{ - flush_workqueue(workqueue); + /* + * We use the system_freezable_wq, because of two reasons. + * First, it allows several works (not the same work item) to be + * executed simultaneously. Second, the queue becomes frozen when + * userspace becomes frozen during system PM. + */ + return queue_delayed_work(system_freezable_wq, work, delay); } #ifdef CONFIG_FAIL_MMC_REQUEST @@ -2669,7 +2663,6 @@ void mmc_stop_host(struct mmc_host *host) host->rescan_disable = 1; cancel_delayed_work_sync(&host->detect); - mmc_flush_scheduled_work(); /* clear pm flags now and let card drivers set them as needed */ host->pm_flags = 0; @@ -2852,13 +2845,9 @@ static int __init mmc_init(void) { int ret; - workqueue = alloc_ordered_workqueue("kmmcd", 0); - if (!workqueue) - return -ENOMEM; - ret = mmc_register_bus(); if (ret) - goto destroy_workqueue; + return ret; ret = mmc_register_host_class(); if (ret) @@ -2874,9 +2863,6 @@ unregister_host_class: mmc_unregister_host_class(); unregister_bus: mmc_unregister_bus(); -destroy_workqueue: - destroy_workqueue(workqueue); - return ret; } @@ -2885,7 +2871,6 @@ static void __exit mmc_exit(void) sdio_unregister_bus(); mmc_unregister_host_class(); mmc_unregister_bus(); - destroy_workqueue(workqueue); } subsys_initcall(mmc_init);
The mmc workqueue is an ordered workqueue, allowing only one work to execute per given time. As this workqueue is used for card detection, the conseqeunce is that cards will be detected one by one waiting for each other. Moreover, most of the time spent during card initialization is waiting for the card's internal firmware to be ready. From a CPU perspective this typically means waiting for a completion variable to be kicked via an IRQ-handler or waiting for a sleep timer to finish. This behaviour of detecting/initializing cards is sub-optimal, especially for SOCs having several controllers/cards. Let's convert to use the system_freezable_wq for the mmc detect works. This enables several works to be executed simultaneously and thus also cards to be detected like so. Tests on UX500, which holds two eMMC cards and an SD-card (actually also an SDIO card, currently not detected), shows a significant improved behaviour due to this change. Before this change, both the eMMC cards waited for the SD card to be initialized as its detect work entered the workqueue first. In some cases, depending on the characteristic of the SD-card, they got delayed 1-1.5 s. Additionally for the second eMMC, it needed to wait for the first eMMC to be initialized which added another 120-190 ms. Converting to the system_freezable_wq, removed these delays and made both the eMMC cards available far earlier in the boot sequence. Selecting the system_freezable_wq, in favour of for example the system_wq, is because we need card detection mechanism to be disabled once userspace are frozen during system PM. Currently the mmc core deal with this via PM notifiers, but following patches may utilize the behaviour of the system_freezable_wq, to simplify the use of the PM notifiers. Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org> --- drivers/mmc/core/core.c | 31 ++++++++----------------------- 1 file changed, 8 insertions(+), 23 deletions(-) -- 1.9.1