On 12/06/2017 12:20, Jan Kara wrote: > Hello, > > On Fri 09-06-17 16:20:49, Laurent Dufour wrote: >> This is a port on kernel 4.12 of the work done by Peter Zijlstra to >> handle page fault without holding the mm semaphore. >> >> http://linux-kernel.2935.n7.nabble.com/RFC-PATCH-0-6-Another-go-at-speculative-page-faults-tt965642.html#none >> >> Compared to the Peter initial work, this series introduce a try spin >> lock when dealing with speculative page fault. This is required to >> avoid dead lock when handling a page fault while a TLB invalidate is >> requested by an other CPU holding the PTE. Another change due to a >> lock dependency issue with mapping->i_mmap_rwsem. >> >> This series also protect changes to VMA's data which are read or >> change by the page fault handler. The protections is done through the >> VMA's sequence number. >> >> This series is functional on x86 and PowerPC. >> >> It's building on top of v4.12-rc4 and relies on the change done by >> Paul McKenney to the SRCU code allowing better performance by >> maintaining per-CPU callback lists: >> >> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=da915ad5cf25b5f5d358dd3670c3378d8ae8c03e >> >> Tests have been made using a large commercial in-memory database on a >> PowerPC system with 752 CPUs. The results are very encouraging since >> the loading of the 2TB database was faster by 20% with the speculative >> page fault. >> >> Since tests are encouraging and running test suite didn't raise any >> issue, I'd like this request for comment series to move to a patch >> series soon. So please feel free to comment. > > I had a look at the series and I have one comment regarding the whole > structure of the series: Instead of taking original Peter's patches and > then fixing up various problems with them, either fold the fixes into > original patches which introduced problems (this would make sense for > example for the lock inversion issue you fix) or just put these changes > to a place in the series where they logically belong - e.g. VMA is > protected by the sequence counter in patch 4 and then you add various > places that were missed later in the series. Instead of this just handle > sequence count protection in consecutive logical steps like vma_adjust() > changes, mremap() changes, munmap() changes, vma->flags protection, ... Thanks Jan for the review, I tried to keep the Peter's patches intact, but I agree, that may not be a good idea, and I tend to split this series in too much small patches. I think I'll fold the changes I made into the original patches, this may also fix some build test issue raised earlier. > Also amount of 'XXX' comments seems to be a bit to high and these should be > addressed. Right, I'll get rid of them ! Thanks, Laurent. > > Honza >> >> Changes since V3: >> - support for the 5-level paging. >> - abort speculative path before entering userfault code >> - support for PowerPC architecture >> - reorder the patch to fix build test errors. >> >> Laurent Dufour (14): >> mm: Introduce pte_spinlock >> mm/spf: Try spin lock in speculative path >> mm/spf: Fix fe.sequence init in __handle_mm_fault() >> mm/spf: don't set fault entry's fields if locking failed >> mm/spf; fix lock dependency against mapping->i_mmap_rwsem >> mm/spf: Protect changes to vm_flags >> mm/spf Protect vm_policy's changes against speculative pf >> mm/spf: Add check on the VMA's flags >> mm/spf: protect madvise vs speculative pf >> mm/spf: protect mremap() against speculative pf >> mm/spf: Don't call user fault callback in the speculative path >> x86/mm: Update the handle_speculative_fault's path >> powerpc/mm: Add speculative page fault >> mm/spf: Clear FAULT_FLAG_KILLABLE in the speculative path >> >> Peter Zijlstra (6): >> mm: Dont assume page-table invariance during faults >> mm: Prepare for FAULT_FLAG_SPECULATIVE >> mm: VMA sequence count >> mm: RCU free VMAs >> mm: Provide speculative fault infrastructure >> x86/mm: Add speculative pagefault handling >> >> arch/powerpc/mm/fault.c | 25 +++- >> arch/x86/mm/fault.c | 14 +++ >> fs/proc/task_mmu.c | 2 + >> include/linux/mm.h | 4 + >> include/linux/mm_types.h | 3 + >> kernel/fork.c | 1 + >> mm/init-mm.c | 1 + >> mm/internal.h | 20 ++++ >> mm/madvise.c | 4 + >> mm/memory.c | 291 +++++++++++++++++++++++++++++++++++++++-------- >> mm/mempolicy.c | 10 +- >> mm/mlock.c | 9 +- >> mm/mmap.c | 123 +++++++++++++++----- >> mm/mprotect.c | 2 + >> mm/mremap.c | 7 ++ >> 15 files changed, 435 insertions(+), 81 deletions(-) >> >> -- >> 2.7.4 >> -- 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>
