On 11/22/23 12:35, Chengming Zhou wrote: > On 2023/11/22 17:37, Vlastimil Babka wrote: >> On 11/20/23 19:49, Mark Brown wrote: >>> On Thu, Nov 02, 2023 at 03:23:27AM +0000, chengming.zhou@xxxxxxxxx wrote: >>>> From: Chengming Zhou <zhouchengming@xxxxxxxxxxxxx> >>>> >>>> Now we will freeze slabs when moving them out of node partial list to >>>> cpu partial list, this method needs two cmpxchg_double operations: >>>> >>>> 1. freeze slab (acquire_slab()) under the node list_lock >>>> 2. get_freelist() when pick used in ___slab_alloc() >>> >>> Recently -next has been failing to boot on a Raspberry Pi 3 with an arm >>> multi_v7_defconfig and a NFS rootfs, a bisect appears to point to this >>> patch (in -next as c8d312e039030edab25836a326bcaeb2a3d4db14) as having >>> introduced the issue. I've included the full bisect log below. >>> >>> When we see problems we see RCU stalls while logging in, for example: >> >> Can you try this, please? >> > > Great! I manually disabled __CMPXCHG_DOUBLE to reproduce the problem, > and this patch can solve the machine hang problem. > > BTW, I also did the performance testcase on the machine with 128 CPUs. > > stress-ng --rawpkt 128 --rawpkt-ops 100000000 > > base patched > 2.22s 2.35s > 2.21s 3.14s > 2.19s 4.75s > > Found this atomic version performance numbers are not stable. That's weirdly too bad. Is that measured also with __CMPXCHG_DOUBLE disabled, or just the patch? The PG_workingset flag change should be uncontended as we are doing it under list_lock, and with __CMPXCHG_DOUBLE there should be no interfering PG_locked interference.
