| Message ID | 20200403112928.19742-5-kirill.shutemov@linux.intel.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | thp/khugepaged improvements and CoW semantics | expand |
On 3 Apr 2020, at 7:29, Kirill A. Shutemov wrote: > External email: Use caution opening links or attachments > > > __collapse_huge_page_isolate() may fail due to extra pin in the LRU add > pagevec. It's petty common for swapin case: we swap in pages just to s/petty/pretty > fail due to the extra pin. > > Drain LRU add pagevec on sucessfull swapin. s/sucessfull/successful > > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> > --- > mm/khugepaged.c | 5 +++++ > 1 file changed, 5 insertions(+) > > diff --git a/mm/khugepaged.c b/mm/khugepaged.c > index fdc10ffde1ca..57ff287caf6b 100644 > --- a/mm/khugepaged.c > +++ b/mm/khugepaged.c > @@ -940,6 +940,11 @@ static bool __collapse_huge_page_swapin(struct mm_struct *mm, > } > vmf.pte--; > pte_unmap(vmf.pte); > + > + /* Drain LRU add pagevec to remove extra pin on the swapped in pages */ > + if (swapped_in) > + lru_add_drain(); > + > trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 1); > return true; > } > -- > 2.26.0 — Best Regards, Yan Zi
On 4/3/20 4:29 AM, Kirill A. Shutemov wrote: > __collapse_huge_page_isolate() may fail due to extra pin in the LRU add > pagevec. It's petty common for swapin case: we swap in pages just to > fail due to the extra pin. > > Drain LRU add pagevec on sucessfull swapin. > > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> > --- > mm/khugepaged.c | 5 +++++ > 1 file changed, 5 insertions(+) > > diff --git a/mm/khugepaged.c b/mm/khugepaged.c > index fdc10ffde1ca..57ff287caf6b 100644 > --- a/mm/khugepaged.c > +++ b/mm/khugepaged.c > @@ -940,6 +940,11 @@ static bool __collapse_huge_page_swapin(struct mm_struct *mm, > } > vmf.pte--; > pte_unmap(vmf.pte); > + > + /* Drain LRU add pagevec to remove extra pin on the swapped in pages */ > + if (swapped_in) > + lru_add_drain(); There is already lru_add_drain() called in swap readahead path, please see swap_vma_readahead() and swap_cluster_readahead(). The extra call to draining lru seems unnecessary. > + > trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 1); > return true; > }
On Mon, Apr 06, 2020 at 11:29:11AM -0700, Yang Shi wrote: > > > On 4/3/20 4:29 AM, Kirill A. Shutemov wrote: > > __collapse_huge_page_isolate() may fail due to extra pin in the LRU add > > pagevec. It's petty common for swapin case: we swap in pages just to > > fail due to the extra pin. > > > > Drain LRU add pagevec on sucessfull swapin. > > > > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> > > --- > > mm/khugepaged.c | 5 +++++ > > 1 file changed, 5 insertions(+) > > > > diff --git a/mm/khugepaged.c b/mm/khugepaged.c > > index fdc10ffde1ca..57ff287caf6b 100644 > > --- a/mm/khugepaged.c > > +++ b/mm/khugepaged.c > > @@ -940,6 +940,11 @@ static bool __collapse_huge_page_swapin(struct mm_struct *mm, > > } > > vmf.pte--; > > pte_unmap(vmf.pte); > > + > > + /* Drain LRU add pagevec to remove extra pin on the swapped in pages */ > > + if (swapped_in) > > + lru_add_drain(); > > There is already lru_add_drain() called in swap readahead path, please see > swap_vma_readahead() and swap_cluster_readahead(). But not for synchronous case. See SWP_SYNCHRONOUS_IO branch in do_swap_page(). Maybe we should drain it in swap_readpage() or in do_swap_page() after swap_readpage()? I donno.
On 4/8/20 6:05 AM, Kirill A. Shutemov wrote: > On Mon, Apr 06, 2020 at 11:29:11AM -0700, Yang Shi wrote: >> >> On 4/3/20 4:29 AM, Kirill A. Shutemov wrote: >>> __collapse_huge_page_isolate() may fail due to extra pin in the LRU add >>> pagevec. It's petty common for swapin case: we swap in pages just to >>> fail due to the extra pin. >>> >>> Drain LRU add pagevec on sucessfull swapin. >>> >>> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> >>> --- >>> mm/khugepaged.c | 5 +++++ >>> 1 file changed, 5 insertions(+) >>> >>> diff --git a/mm/khugepaged.c b/mm/khugepaged.c >>> index fdc10ffde1ca..57ff287caf6b 100644 >>> --- a/mm/khugepaged.c >>> +++ b/mm/khugepaged.c >>> @@ -940,6 +940,11 @@ static bool __collapse_huge_page_swapin(struct mm_struct *mm, >>> } >>> vmf.pte--; >>> pte_unmap(vmf.pte); >>> + >>> + /* Drain LRU add pagevec to remove extra pin on the swapped in pages */ >>> + if (swapped_in) >>> + lru_add_drain(); >> There is already lru_add_drain() called in swap readahead path, please see >> swap_vma_readahead() and swap_cluster_readahead(). > But not for synchronous case. See SWP_SYNCHRONOUS_IO branch in > do_swap_page(). Aha, yes. I missed the synchronous case. > > Maybe we should drain it in swap_readpage() or in do_swap_page() after > swap_readpage()? I donno. It may be better to keep it as is. Draining lru for every page for synchronous case in do_swap_page() path sounds not very productive. Doing it in khugepaged seems acceptable. We just drain lru cache again for non-synchronous case, but the cache may be already empty so it should take very short time since nothing to drain. >
diff --git a/mm/khugepaged.c b/mm/khugepaged.c index fdc10ffde1ca..57ff287caf6b 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -940,6 +940,11 @@ static bool __collapse_huge_page_swapin(struct mm_struct *mm, } vmf.pte--; pte_unmap(vmf.pte); + + /* Drain LRU add pagevec to remove extra pin on the swapped in pages */ + if (swapped_in) + lru_add_drain(); + trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 1); return true; }
__collapse_huge_page_isolate() may fail due to extra pin in the LRU add pagevec. It's petty common for swapin case: we swap in pages just to fail due to the extra pin. Drain LRU add pagevec on sucessfull swapin. Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> --- mm/khugepaged.c | 5 +++++ 1 file changed, 5 insertions(+)