On Mon, Jun 20, 2016 at 10:51:25AM +0800, Hillf Danton wrote: > > > > > @@ -2401,11 +2430,18 @@ static void __collapse_huge_page_swapin(struct mm_struct *mm, > > > > > continue; > > > > > swapped_in++; > > > > > ret = do_swap_page(mm, vma, _address, pte, pmd, > > > > > - FAULT_FLAG_ALLOW_RETRY|FAULT_FLAG_RETRY_NOWAIT, > > > > > + FAULT_FLAG_ALLOW_RETRY, > > > > > > > > Add a description in change log for it please. > > > > > > Ebru, would you address it? > > > > > This changelog really seems poor. > > Is there a way to update only changelog of the commit? > > I tried to use git rebase to amend commit, however > > I could not rebase. This patch only needs better changelog. > > > > I would like to update it as follows, if you would like to too: > > > > " > > Currently khugepaged makes swapin readahead under down_write. This patch > > supplies to make swapin readahead under down_read instead of down_write. > > > > Along swapin, we can need to drop and re-take mmap_sem. Therefore we > > have to be sure vma is consistent. This patch adds a helper function > > to validate vma and also supplies that async swapin should not be > > performed without waiting. > > > > The patch was tested with a test program that allocates 800MB of memory, > > writes to it, and then sleeps. The system was forced to swap out all. > > Afterwards, the test program touches the area by writing, it skips a page > > in each 20 pages of the area. > > " > > > I like to ask again, why is FAULT_FLAG_RETRY_NOWAIT dropped? > I dropped it regarding to Hugh's concern. If I understood correctly, he said async swapin without waiting can cause waste. When I looked the code path, it seemed subtle to me. There was a large discussion, below is Hugh's concern: " Doesn't this imply that __collapse_huge_page_swapin() will initiate all the necessary swapins for a THP, then (given the FAULT_FLAG_ALLOW_RETRY) not wait for them to complete, so khugepaged will give up on that extent and move on to another; then after another full circuit of all the mms it needs to examine, it will arrive back at this extent and build a THP from the swapins it arranged last time. Which may work well when a system transitions from busy+swappingout to idle+swappingin, but isn't that rather a special case? It feels (meaning, I've not measured at all) as if the inbetween busyish case will waste a lot of I/O and memory on swapins that have to be discarded again before khugepaged has made its sedate way back to slotting them in. " Cc'ed Hugh. Maybe I misunderstood him. > > Could you please suggest me a way to replace above changelog with the old? > > > We can ask Andrew for some advices. > > > > > > > > > They are cleaned up in subsequent darns? > > > > > Yes, that is reported and fixed here: > > http://git.kernel.org/cgit/linux/kernel/git/next/linux-next.git/commit/?id=fc7038a69cee6b817261f7cd805e9663fdc1075c > > > > However, the above comment inconsistency still there. > > I've added a fix patch: > > > > From 404438ff1b0617cbf7434cba0c5a08f79ccb8a5d Mon Sep 17 00:00:00 2001 > > From: Ebru Akagunduz <ebru.akagunduz@xxxxxxxxx> > > Date: Sat, 18 Jun 2016 21:07:22 +0300 > > Subject: [PATCH] mm, thp: fix comment inconsistency for swapin readahead > > functions > > > Fill in change log please. > I filled it and sent as part of a series. Cc'ed you in that patch. > thanks > Hillf > > > Signed-off-by: Ebru Akagunduz <ebru.akagunduz@xxxxxxxxx> > > --- > > mm/huge_memory.c | 9 +++++---- > > 1 file changed, 5 insertions(+), 4 deletions(-) > > > > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > > index acd374e..f0d528e 100644 > > --- a/mm/huge_memory.c > > +++ b/mm/huge_memory.c > > @@ -2436,9 +2436,10 @@ static bool __collapse_huge_page_swapin(struct mm_struct *mm, > > /* do_swap_page returns VM_FAULT_RETRY with released mmap_sem */ > > if (ret & VM_FAULT_RETRY) { > > down_read(&mm->mmap_sem); > > - /* vma is no longer available, don't continue to swapin */ > > - if (hugepage_vma_revalidate(mm, address)) > > + if (hugepage_vma_revalidate(mm, address)) { > > + /* vma is no longer available, don't continue to swapin */ > > return false; > > + } > > } > > if (ret & VM_FAULT_ERROR) { > > trace_mm_collapse_huge_page_swapin(mm, swapped_in, 0); > > @@ -2513,8 +2514,8 @@ static void collapse_huge_page(struct mm_struct *mm, > > if (allocstall == curr_allocstall && swap != 0) { > > /* > > * __collapse_huge_page_swapin always returns with mmap_sem > > - * locked. If it fails, release mmap_sem and jump directly > > - * out. Continuing to collapse causes inconsistency. > > + * locked. If it fails, we release mmap_sem and jump out_nolock. > > + * Continuing to collapse causes inconsistency. > > */ > > if (!__collapse_huge_page_swapin(mm, vma, address, pmd)) { > > mem_cgroup_cancel_charge(new_page, memcg, true); > > -- > > 1.9.1 > -- 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>