Hi, Vlastimil I review the code again. it works well for NUMA. because khugepaged_prealloc_page will put_page when *hpage is true. the memory leak will still exist in !NUMA. because it ingore the put_page. is it right? I miss something. Thanks zhongjiang On 2017/5/9 20:41, Vlastimil Babka wrote: > On 05/09/2017 02:20 PM, zhong jiang wrote: >> On 2017/5/9 19:34, Vlastimil Babka wrote: >>> On 05/09/2017 12:55 PM, zhongjiang wrote: >>>> From: zhong jiang <zhongjiang@xxxxxxxxxx> >>>> >>>> Current, when we prepare a huge page to collapse, due to some >>>> reasons, it can fail to collapse. At the moment, we should >>>> release the preallocate huge page. >>>> >>>> Signed-off-by: zhong jiang <zhongjiang@xxxxxxxxxx> >>> Hmm, scratch that, there's no memory leak. The pointer to new_page is >>> stored in *hpage, and put_page() is called all the way up in >>> khugepaged_do_scan(). >> I see. I miss it. but why the new_page need to be release all the way. > AFAIK to support preallocation and reusal of preallocated page for > collapse attempt in different pmd. It only works for !NUMA so it's > likely not worth all the trouble and complicated code, so I wouldn't be > opposed to simplifying this. > >> I do not see the count increment when scan success. it save the memory, >> only when page fault happen. > I don't understand what you mean here? > >> Thanks >> zhongjiang >>>> --- >>>> mm/khugepaged.c | 4 ++++ >>>> 1 file changed, 4 insertions(+) >>>> >>>> diff --git a/mm/khugepaged.c b/mm/khugepaged.c >>>> index 7cb9c88..586b1f1 100644 >>>> --- a/mm/khugepaged.c >>>> +++ b/mm/khugepaged.c >>>> @@ -1082,6 +1082,8 @@ static void collapse_huge_page(struct mm_struct *mm, >>>> up_write(&mm->mmap_sem); >>>> out_nolock: >>>> trace_mm_collapse_huge_page(mm, isolated, result); >>>> + if (page != NULL && result != SCAN_SUCCEED) >>>> + put_page(new_page); >>>> return; >>>> out: >>>> mem_cgroup_cancel_charge(new_page, memcg, true); >>>> @@ -1555,6 +1557,8 @@ static void collapse_shmem(struct mm_struct *mm, >>>> } >>>> out: >>>> VM_BUG_ON(!list_empty(&pagelist)); >>>> + if (page != NULL && result != SCAN_SUCCEED) >>>> + put_page(new_page); >>>> /* TODO: tracepoints */ >>>> } >>>> >>>> >>> . >>> >> > > . > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
