| Message ID | 1600204258-13683-2-git-send-email-vijayb@linux.microsoft.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v2,1/2] mm: khugepaged: recalculate min_free_kbytes after memory hotplug as expected by khugepaged | expand |
On Tue 15-09-20 14:10:58, Vijay Balakrishna wrote: > set_recommended_min_free_kbytes need to honor min_free_kbytes set by the > user. Post start-of-day THP enable or memory hotplug operations can > lose user specified min_free_kbytes, in particular when it is higher than > calculated recommended value. Also modifying "recommended_min" variable > type to "int" from "unsigned long" to avoid undesired result noticed > during testing. It is due to comparing "unsigned long" with "int" type. > > Signed-off-by: Vijay Balakrishna <vijayb@linux.microsoft.com> > Cc: stable@vger.kernel.org > Reviewed-by: Pavel Tatashin <pasha.tatashin@soleen.com> > --- > mm/khugepaged.c | 8 ++++---- > 1 file changed, 4 insertions(+), 4 deletions(-) > > diff --git a/mm/khugepaged.c b/mm/khugepaged.c > index 4f7107476a6f..b4b753ba411a 100644 > --- a/mm/khugepaged.c > +++ b/mm/khugepaged.c > @@ -2253,7 +2253,7 @@ static void set_recommended_min_free_kbytes(void) > { > struct zone *zone; > int nr_zones = 0; > - unsigned long recommended_min; > + int recommended_min; > > for_each_populated_zone(zone) { > /* > @@ -2280,12 +2280,12 @@ static void set_recommended_min_free_kbytes(void) > > /* don't ever allow to reserve more than 5% of the lowmem */ > recommended_min = min(recommended_min, > - (unsigned long) nr_free_buffer_pages() / 20); > + (int) nr_free_buffer_pages() / 20); nr_free_buffer_pages can oveflow in int on very large machines. > recommended_min <<= (PAGE_SHIFT-10); > > - if (recommended_min > min_free_kbytes) { > + if (recommended_min > user_min_free_kbytes) { This can decrease the size theoretically. Because user_min_free_kbytes is -1 by default and recommended_min might be <= min_free_kbytes. You need to check both. Also can we make user_min_free_kbytes 0 by default? From a quick look, nobody should really care. > if (user_min_free_kbytes >= 0) > - pr_info("raising min_free_kbytes from %d to %lu to help transparent hugepage allocations\n", > + pr_info("raising min_free_kbytes from %d to %d to help transparent hugepage allocations\n", > min_free_kbytes, recommended_min); > > min_free_kbytes = recommended_min; > -- > 2.28.0 >
On 9/16/2020 12:59 AM, Michal Hocko wrote: > On Tue 15-09-20 14:10:58, Vijay Balakrishna wrote: >> set_recommended_min_free_kbytes need to honor min_free_kbytes set by the >> user. Post start-of-day THP enable or memory hotplug operations can >> lose user specified min_free_kbytes, in particular when it is higher than >> calculated recommended value. Also modifying "recommended_min" variable >> type to "int" from "unsigned long" to avoid undesired result noticed >> during testing. It is due to comparing "unsigned long" with "int" type. >> >> Signed-off-by: Vijay Balakrishna <vijayb@linux.microsoft.com> >> Cc: stable@vger.kernel.org >> Reviewed-by: Pavel Tatashin <pasha.tatashin@soleen.com> >> --- >> mm/khugepaged.c | 8 ++++---- >> 1 file changed, 4 insertions(+), 4 deletions(-) >> >> diff --git a/mm/khugepaged.c b/mm/khugepaged.c >> index 4f7107476a6f..b4b753ba411a 100644 >> --- a/mm/khugepaged.c >> +++ b/mm/khugepaged.c >> @@ -2253,7 +2253,7 @@ static void set_recommended_min_free_kbytes(void) >> { >> struct zone *zone; >> int nr_zones = 0; >> - unsigned long recommended_min; >> + int recommended_min; >> >> for_each_populated_zone(zone) { >> /* >> @@ -2280,12 +2280,12 @@ static void set_recommended_min_free_kbytes(void) >> >> /* don't ever allow to reserve more than 5% of the lowmem */ >> recommended_min = min(recommended_min, >> - (unsigned long) nr_free_buffer_pages() / 20); >> + (int) nr_free_buffer_pages() / 20); > > nr_free_buffer_pages can oveflow in int on very large machines. Good point. I will address it. > >> recommended_min <<= (PAGE_SHIFT-10); >> >> - if (recommended_min > min_free_kbytes) { >> + if (recommended_min > user_min_free_kbytes) { > > This can decrease the size theoretically. Because user_min_free_kbytes > is -1 by default and recommended_min might be <= min_free_kbytes. > > You need to check both. Also can we make user_min_free_kbytes 0 by > default? From a quick look, nobody should really care. Let me rework. Thanks, Vijay > >> if (user_min_free_kbytes >= 0) >> - pr_info("raising min_free_kbytes from %d to %lu to help transparent hugepage allocations\n", >> + pr_info("raising min_free_kbytes from %d to %d to help transparent hugepage allocations\n", >> min_free_kbytes, recommended_min); >> >> min_free_kbytes = recommended_min; >> -- >> 2.28.0 >> >
diff --git a/mm/khugepaged.c b/mm/khugepaged.c index 4f7107476a6f..b4b753ba411a 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -2253,7 +2253,7 @@ static void set_recommended_min_free_kbytes(void) { struct zone *zone; int nr_zones = 0; - unsigned long recommended_min; + int recommended_min; for_each_populated_zone(zone) { /* @@ -2280,12 +2280,12 @@ static void set_recommended_min_free_kbytes(void) /* don't ever allow to reserve more than 5% of the lowmem */ recommended_min = min(recommended_min, - (unsigned long) nr_free_buffer_pages() / 20); + (int) nr_free_buffer_pages() / 20); recommended_min <<= (PAGE_SHIFT-10); - if (recommended_min > min_free_kbytes) { + if (recommended_min > user_min_free_kbytes) { if (user_min_free_kbytes >= 0) - pr_info("raising min_free_kbytes from %d to %lu to help transparent hugepage allocations\n", + pr_info("raising min_free_kbytes from %d to %d to help transparent hugepage allocations\n", min_free_kbytes, recommended_min); min_free_kbytes = recommended_min;