On 8/26/22 12:55, Jan Kara wrote: > On Thu 25-08-22 11:05:48, matoro wrote: >> Hello all, I know this is quite an old thread. I recently acquired some >> alpha hardware and have run into this exact same problem on the latest >> stable kernel (5.18 and 5.19). CONFIG_COMPACTION seems to be totally broken >> and causes userspace to be extremely unstable - random segfaults, corruption >> of glibc data structures, gcc ICEs etc etc - seems most noticable during >> tasks with heavy I/O load. >> >> My hardware is a DS15 (Titan), so only slightly newer than the Tsunamis >> mentioned earlier. The problem is greatly exacerbated when using a >> machine-optimized kernel (CONFIG_ALPHA_TITAN) over one with >> CONFIG_ALPHA_GENERIC. But it still doesn't go away on a generic kernel, >> just pops up less often, usually very I/O heavy tasks like checking out a >> tag in the kernel repo. >> >> However all of this seems to be dependent on CONFIG_COMPACTION. With this >> toggled off all problems disappear, regardless of other options. I tried >> reverting the commit 88dbcbb3a4847f5e6dfeae952d3105497700c128 mentioned >> earlier in the thread (the structure has moved to a different file but was >> otherwise the same), but it unfortunately did not make a difference. >> >> Since this doesn't seem to have a known cause or an easy fix, would it be >> reasonable to just add a Kconfig dep to disable it automatically on alpha? > > Thanks for report. I guess this just confirms that migration of pagecache > pages is somehow broken on Alpha. Maybe we are missing to flush some cache > specific for Alpha? Or maybe the page migration code is not safe wrt the > peculiar memory ordering Alpha has... I think this will need someone with > Alpha HW and willingness to dive into MM internals to debug this. Added > Vlasta to CC mostly for awareness and in case it rings some bells :). Hi, doesn't ring any bells unfortunately. Does corruption also happen when mmapping a file and applying mbind() with MPOL_MF_MOVE or migrate_pages()? That should allow more controlled migration experimens than through compaction. But that would also need a NUMA machine or a fakenuma support, dunno if alpha has that?
