On Fri, Sep 1, 2023 at 10:26 PM wolfgang huang <wolfgang9277@xxxxxxx> wrote: > > From: wolfgang huang <huangjinhui@xxxxxxxxxx> > > In the 64k page configuration of ARM64, the size of THP is 512MB, > which usually reserves almost 5% of memory. However, the probability > of THP usage is not high, especially in the madvise configure. and > THP is not usually used, but a large amount of memory is reserved > for THP use, resulting in a lot of memory waste. > > So a dynamic method of adjusting reserved memory is proposed. when > scan and trying to merge into THP, the reserved memory is pulled up, > and when the system does not need to synthesize THP, the reserved > memory is kept low. this method can save a lot of memory in scenarios > without synthesizing THP, and can effectively pull up the reserved > memory to support when THP synthesis is needed. especially in the > case of madvise configure, the running effect will be better. > > Signed-off-by: wolfgang huang <huangjinhui@xxxxxxxxxx> Thanks for the patch. There was already a thread about this problem, please refer to: https://lore.kernel.org/linux-mm/20230817035155.84230-1-liusong@xxxxxxxxxxxxxxxxx/ > --- > mm/khugepaged.c | 36 +++++++++++++++++++++++++++++++++++- > 1 file changed, 35 insertions(+), 1 deletion(-) > > diff --git a/mm/khugepaged.c b/mm/khugepaged.c > index 88433cc25d8a..41a837e618a5 100644 > --- a/mm/khugepaged.c > +++ b/mm/khugepaged.c > @@ -129,6 +129,10 @@ static struct khugepaged_scan khugepaged_scan = { > .mm_head = LIST_HEAD_INIT(khugepaged_scan.mm_head), > }; > > +/* khugepaged should scan or not, trying to be thp, default as false */ > +static unsigned int khugepaged_thp_scan_state; > +static void set_recommended_min_free_kbytes(void); > + > #ifdef CONFIG_SYSFS > static ssize_t scan_sleep_millisecs_show(struct kobject *kobj, > struct kobj_attribute *attr, > @@ -2549,6 +2553,33 @@ static void khugepaged_wait_work(void) > wait_event_freezable(khugepaged_wait, khugepaged_wait_event()); > } > > +static int khugepaged_threshold(void) > +{ > + /* thp size threshold check */ > + if ((PAGE_SIZE << HPAGE_PMD_ORDER) >= SZ_512M) > + return true; > + return false; > +} > + > +static void khugepaged_update_wmarks(void) > +{ > + if (!khugepaged_threshold()) > + return; > + > + /* __khugepaged_enter push khugepaged to work, raise watermark */ > + if (khugepaged_has_work()) { > + /* Once set, do not repeat distrub watermark */ > + if (!khugepaged_thp_scan_state) { > + khugepaged_thp_scan_state = true; > + mutex_lock(&khugepaged_mutex); > + set_recommended_min_free_kbytes(); > + mutex_unlock(&khugepaged_mutex); > + } > + } else { > + khugepaged_thp_scan_state = false; > + } > +} > + > static int khugepaged(void *none) > { > struct khugepaged_mm_slot *mm_slot; > @@ -2559,6 +2590,7 @@ static int khugepaged(void *none) > while (!kthread_should_stop()) { > khugepaged_do_scan(&khugepaged_collapse_control); > khugepaged_wait_work(); > + khugepaged_update_wmarks(); > } > > spin_lock(&khugepaged_mm_lock); > @@ -2576,7 +2608,9 @@ static void set_recommended_min_free_kbytes(void) > int nr_zones = 0; > unsigned long recommended_min; > > - if (!hugepage_flags_enabled()) { > + if (!hugepage_flags_enabled() || > + (khugepaged_threshold() && > + !khugepaged_thp_scan_state)) { > calculate_min_free_kbytes(); > goto update_wmarks; > } > -- > 2.34.1 > >
