在 2023/10/6 23:58, Bob Pearson 写道:
On 10/5/23 10:56, Jason Gunthorpe wrote:
On Thu, Oct 05, 2023 at 07:50:28AM -0700, Bart Van Assche wrote:
On 10/5/23 07:21, Jason Gunthorpe wrote:
Which is why it shows there are locking problems in this code.
Hi Jason,
Since the locking problems have not yet been root-caused, do you
agree that it is safer to revert patch "RDMA/rxe: Add workqueue
support for rxe tasks" rather than trying to fix it?
I don't think that makes the locking problems go away any more that
using a single threaded work queue?
Jason
This is slightly off topic but may still be relevant.
If there are locking bugs they are between the two send side tasks
rxe_completer and rxe_requester which share the send queue and other
state. Bart attempts to fix this by setting max_active to 1 which
limits the ability of these two work queue tasks from interfering.
For completely different reasons we have looked at merging these
two tasks into a single task which it turns out improves performance,
especially in high scale situations where it reduces the number of
cpu cores needed to complete work. But even at low scale (1-2 QPs)
it helps because of improved caching. It turns out that if the work
is mostly sends and writes that there isn't much for the completer
to do while if it is mostly reads there isn't much for the requester
to do. So combining them doesn't hurt performance by having fewer cores
to do the work. But this also prevents the two tasks for a given QP
to run at the same time which should eliminate locking issues.
If no one hates the idea I can send in our patch that does this.
Hi, Bob
The blktest hang problem is not fixed now. I do not think that it is a
good time
to introduce this new feature.
IMHO, we should fix this blktest hang problem. And we also need some time to
wait for the test results from the users. If this problem proves fixed.
Then we have a
stable RXE version for the new feature from you.
In short, we need a stable RXE version for use. Then based on the stable
RXE version,
new features are welcomed.
Please let me know your advice.
Please Bart comment on this.
Please Jason && Leon comment on this.
Warm Regards,
Zhu Yanjun
Bob
