On 10/13/2017 08:14 AM, Khalid Aziz wrote:
On 10/12/2017 02:27 PM, Anthony Yznaga wrote:
On Oct 12, 2017, at 7:44 AM, Khalid Aziz <khalid.aziz@xxxxxxxxxx> wrote:
On 10/06/2017 04:12 PM, Anthony Yznaga wrote:
On Sep 25, 2017, at 9:49 AM, Khalid Aziz <khalid.aziz@xxxxxxxxxx>
wrote:
This patch extends mprotect to enable ADI (TSTATE.mcde),
enable/disable
MCD (Memory Corruption Detection) on selected memory ranges, enable
TTE.mcd in PTEs, return ADI parameters to userspace and
save/restore ADI
version tags on page swap out/in or migration. ADI is not enabled by
I still don't believe migration is properly supported. Your
implementation is relying on a fault happening on a page while its
migration is in progress so that do_swap_page() will be called, but
I don't see how do_swap_page() will be called if a fault does not
happen until after the migration has completed.
User pages are on LRU list and for the mapped pages on LRU list,
migrate_pages() ultimately calls try_to_unmap_one and makes a
migration swap entry for the page being migrated. This forces a page
fault upon access on the destination node and the page is swapped
back in from swap cache. The fault is forced by the migration swap
entry, rather than fault being an accidental event. If page fault
happens on the destination node while migration is in progress,
do_swap_page() waits until migration is done. Please take a look at
the code in __unmap_and_move().
I looked at the code again, and I now believe ADI tags are never
restored for migrated pages. Here's why:
I will take a look at it again. I have run extensive tests migrating
pages of a process across multiple NUMA nodes over and over again and
ADI tags were never lost, so this does work. I won't rule out the
possibility of having missed a code path where tags are not restored and
I will look for it.
Anthony,
I just ran my migration test again which:
- malloc's 16 GB of memory
- Assigns a rotating ADI tag every 64 bytes to the malloc'd buffer
- Writes a pattern to the entire buffer
- Verifies the pattern it wrote using ADI tagged addresses.
While this test was running, I had a script migrate test program pages
across two NUMA nodes every 30 seconds using migratepages command. I did
not see an ADI tag mismatch over multiple runs of this test. This test
shows migration is working.
Can you give me a test that shows the failure you think we should see
and I will debug it.
Thanks,
Khalid
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