| Message ID | 20180615155733.1175-1-pasha.tatashin@oracle.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Fri, Jun 15, 2018 at 11:57:33AM -0400, Pavel Tatashin wrote: > The role of zero_resv_unavail() is to make sure that every struct page that > is allocated but is not backed by memory that is accessible by kernel is > zeroed and not in some uninitialized state. > > Since struct pages are allocated in blocks (2M pages in x86 case), we can > skip pageblock_nr_pages at a time, when the first one is found to be > invalid. > > This optimization may help since now on x86 every hole in e820 maps > is marked as reserved in memblock, and thus will go through this function. > > This function is called before sched_clock() is initialized, so I used my > x86 early boot clock patches to measure the performance improvement. > > With 1T hole on i7-8700 currently we would take 0.606918s of boot time, but > with this optimization 0.001103s. > > Signed-off-by: Pavel Tatashin <pasha.tatashin@oracle.com> > --- > mm/page_alloc.c | 5 ++++- > 1 file changed, 4 insertions(+), 1 deletion(-) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 1521100f1e63..94f1b3201735 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -6404,8 +6404,11 @@ void __paginginit zero_resv_unavail(void) > pgcnt = 0; > for_each_resv_unavail_range(i, &start, &end) { > for (pfn = PFN_DOWN(start); pfn < PFN_UP(end); pfn++) { > - if (!pfn_valid(ALIGN_DOWN(pfn, pageblock_nr_pages))) > + if (!pfn_valid(ALIGN_DOWN(pfn, pageblock_nr_pages))) { > + pfn = ALIGN_DOWN(pfn, pageblock_nr_pages) > + + pageblock_nr_pages - 1; > continue; > + } > mm_zero_struct_page(pfn_to_page(pfn)); > pgcnt++; > } Hi Pavel, Thanks for the patch. This looks good to me. Reviewed-by: Oscar Salvador <osalvador@suse.de> > -- > 2.17.1 > Best Regards Oscar Salvador
> Hi Pavel, > > Thanks for the patch. > This looks good to me. > > Reviewed-by: Oscar Salvador <osalvador@suse.de> Thank you Oscar! Pavel
On Fri, Jun 15, 2018 at 11:57:33AM -0400, Pavel Tatashin wrote: > The role of zero_resv_unavail() is to make sure that every struct page that > is allocated but is not backed by memory that is accessible by kernel is > zeroed and not in some uninitialized state. > > Since struct pages are allocated in blocks (2M pages in x86 case), we can > skip pageblock_nr_pages at a time, when the first one is found to be > invalid. > > This optimization may help since now on x86 every hole in e820 maps > is marked as reserved in memblock, and thus will go through this function. > > This function is called before sched_clock() is initialized, so I used my > x86 early boot clock patches to measure the performance improvement. > > With 1T hole on i7-8700 currently we would take 0.606918s of boot time, but > with this optimization 0.001103s. > > Signed-off-by: Pavel Tatashin <pasha.tatashin@oracle.com> Looks good to me, thanks! Reviewed-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> > --- > mm/page_alloc.c | 5 ++++- > 1 file changed, 4 insertions(+), 1 deletion(-) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 1521100f1e63..94f1b3201735 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -6404,8 +6404,11 @@ void __paginginit zero_resv_unavail(void) > pgcnt = 0; > for_each_resv_unavail_range(i, &start, &end) { > for (pfn = PFN_DOWN(start); pfn < PFN_UP(end); pfn++) { > - if (!pfn_valid(ALIGN_DOWN(pfn, pageblock_nr_pages))) > + if (!pfn_valid(ALIGN_DOWN(pfn, pageblock_nr_pages))) { > + pfn = ALIGN_DOWN(pfn, pageblock_nr_pages) > + + pageblock_nr_pages - 1; > continue; > + } > mm_zero_struct_page(pfn_to_page(pfn)); > pgcnt++; > } > -- > 2.17.1 > >
diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 1521100f1e63..94f1b3201735 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -6404,8 +6404,11 @@ void __paginginit zero_resv_unavail(void) pgcnt = 0; for_each_resv_unavail_range(i, &start, &end) { for (pfn = PFN_DOWN(start); pfn < PFN_UP(end); pfn++) { - if (!pfn_valid(ALIGN_DOWN(pfn, pageblock_nr_pages))) + if (!pfn_valid(ALIGN_DOWN(pfn, pageblock_nr_pages))) { + pfn = ALIGN_DOWN(pfn, pageblock_nr_pages) + + pageblock_nr_pages - 1; continue; + } mm_zero_struct_page(pfn_to_page(pfn)); pgcnt++; }
The role of zero_resv_unavail() is to make sure that every struct page that is allocated but is not backed by memory that is accessible by kernel is zeroed and not in some uninitialized state. Since struct pages are allocated in blocks (2M pages in x86 case), we can skip pageblock_nr_pages at a time, when the first one is found to be invalid. This optimization may help since now on x86 every hole in e820 maps is marked as reserved in memblock, and thus will go through this function. This function is called before sched_clock() is initialized, so I used my x86 early boot clock patches to measure the performance improvement. With 1T hole on i7-8700 currently we would take 0.606918s of boot time, but with this optimization 0.001103s. Signed-off-by: Pavel Tatashin <pasha.tatashin@oracle.com> --- mm/page_alloc.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)