Messages in this thread | | | Subject | Re: [PATCH v4 3/4] mm/page_reporting: Allow driver to specify reporting order | From | Gavin Shan <> | Date | Fri, 25 Jun 2021 16:04:38 +1000 |
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On 6/25/21 3:48 PM, Michael S. Tsirkin wrote: > On Fri, Jun 25, 2021 at 09:47:09AM +0800, Gavin Shan wrote: >> The page reporting order (threshold) is sticky to @pageblock_order >> by default. The page reporting can never be triggered because the >> freeing page can't come up with a free area like that huge. The >> situation becomes worse when the system memory becomes heavily >> fragmented. >> >> For example, the following configurations are used on ARM64 when 64KB >> base page size is enabled. In this specific case, the page reporting >> won't be triggered until the freeing page comes up with a 512MB free >> area. That's hard to be met, especially when the system memory becomes >> heavily fragmented. >> >> PAGE_SIZE: 64KB >> HPAGE_SIZE: 512MB >> pageblock_order: 13 (512MB) >> MAX_ORDER: 14 >> >> This allows the drivers to specify the page reporting order when the >> page reporting device is registered. It falls back to @pageblock_order >> if it's not specified by the driver. The existing users (hv_balloon >> and virtio_balloon) don't specify it and @pageblock_order is still >> taken as their page reporting order. So this shouldn't introduce any >> functional changes. >> >> Signed-off-by: Gavin Shan <gshan@redhat.com> >> Reviewed-by: Alexander Duyck <alexanderduyck@fb.com> >> --- >> include/linux/page_reporting.h | 3 +++ >> mm/page_reporting.c | 6 ++++++ >> 2 files changed, 9 insertions(+) >> >> diff --git a/include/linux/page_reporting.h b/include/linux/page_reporting.h >> index 3b99e0ec24f2..fe648dfa3a7c 100644 >> --- a/include/linux/page_reporting.h >> +++ b/include/linux/page_reporting.h >> @@ -18,6 +18,9 @@ struct page_reporting_dev_info { >> >> /* Current state of page reporting */ >> atomic_t state; >> + >> + /* Minimal order of page reporting */ >> + unsigned int order; >> }; >> >> /* Tear-down and bring-up for page reporting devices */ >> diff --git a/mm/page_reporting.c b/mm/page_reporting.c >> index 34bf4d26c2c4..382958eef8a9 100644 >> --- a/mm/page_reporting.c >> +++ b/mm/page_reporting.c >> @@ -329,6 +329,12 @@ int page_reporting_register(struct page_reporting_dev_info *prdev) >> goto err_out; >> } >> >> + /* >> + * Update the page reporting order if it's specified by driver. >> + * Otherwise, it falls back to @pageblock_order. >> + */ >> + page_reporting_order = prdev->order ? : pageblock_order; >> + > > Hmm. So on ARM achitectures with 64K pages, the command line parameter > is silently ignored? > > Isn't this a problem? >
It's fine as the command line parameter is used as debugging purpose. Besides, it can be changed by writing to the following file:
/sys/module/page_reporting/parameters/page_reporting_order
>> /* initialize state and work structures */ >> atomic_set(&prdev->state, PAGE_REPORTING_IDLE); >> INIT_DELAYED_WORK(&prdev->work, &page_reporting_process); >> -- >> 2.23.0
Thanks, Gavin
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