On Sat, Sep 28, 2024 at 1:43 AM Bernd Schubert <bernd.schubert@xxxxxxxxxxx> wrote: > > Hi Joanne, > > On 9/27/24 21:36, Joanne Koong wrote: > > On Mon, Sep 2, 2024 at 3:38 AM Miklos Szeredi <miklos@xxxxxxxxxx> wrote: > >> > >> On Fri, 30 Aug 2024 at 18:27, Joanne Koong <joannelkoong@xxxxxxxxx> wrote: > >>> > >>> There are situations where fuse servers can become unresponsive or > >>> stuck, for example if the server is in a deadlock. Currently, there's > >>> no good way to detect if a server is stuck and needs to be killed > >>> manually. > >>> > >>> This commit adds an option for enforcing a timeout (in seconds) on > >>> requests where if the timeout elapses without a reply from the server, > >>> the connection will be automatically aborted. > >> > >> Okay. > >> > >> I'm not sure what the overhead (scheduling and memory) of timers, but > >> starting one for each request seems excessive. > > > > I ran some benchmarks on this using the passthrough_ll server and saw > > roughly a 1.5% drop in throughput (from ~775 MiB/s to ~765 MiB/s): > > fio --name randwrite --ioengine=sync --thread --invalidate=1 > > --runtime=300 --ramp_time=10 --rw=randwrite --size=1G --numjobs=4 > > --bs=4k --alloc-size 98304 --allrandrepeat=1 --randseed=12345 > > --group_reporting=1 --directory=/root/fuse_mount > > > > Instead of attaching a timer to each request, I think we can instead > > do the following: > > * add a "start_time" field to each request tracking (in jiffies) when > > the request was started > > * add a new list to the connection that all requests get enqueued > > onto. When the request is completed, it gets dequeued from this list > > * have a timer for the connection that fires off every 10 seconds or > > so. When this timer is fired, it checks if "jiffies > req->start_time > > + fc->req_timeout" against the head of the list to check if the > > timeout has expired and we need to abort the request. We only need to > > check against the head of the list because we know every other request > > after this was started later in time. I think we could even just use > > the fc->lock for this instead of needing a separate lock. In the worst > > case, this grants a 10 second upper bound on the timeout a user > > requests (eg if the user requests 2 minutes, in the worst case the > > timeout would trigger at 2 minutes and 10 seconds). > > > > Also, now that we're aborting the connection entirely on a timeout > > instead of just aborting the request, maybe it makes sense to change > > the timeout granularity to minutes instead of seconds. I'm envisioning > > that this timeout mechanism will mostly be used as a safeguard against > > malicious or buggy servers with a high timeout configured (eg 10 > > minutes), and minutes seems like a nicer interface for users than them > > having to convert that to seconds. > > > > Let me know if I've missed anything with this approach but if not, > > then I'll submit v7 with this change. > > > sounds great to me. Just, could we do this per fuse_dev to avoid a > single lock for all cores? > Will do! thanks for the suggestion - in that case, I'll add its own spinlock for it too then. Thanks, Joanne > > Thanks, > Bernd
