On 05/09/2017 03:31 PM, zhong jiang wrote: > 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? > I mean that whether collapse huge page success or nor, preallocate page will > alway be release. by the above description. I seems to true. Ah, no. In case of success, collapse_huge_page() does *hpage = NULL; so the put_page() won't get to it anymore. > > Thanks > zhongjiang >>> 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>
