"Michael S. Tsirkin" <mst@xxxxxxxxxx> writes: > On Sat, Aug 08, 2015 at 07:06:38PM -0400, Bandan Das wrote: >> Hi Michael, ... >> >> > - does the design address the issue of VM 1 being blocked >> > (e.g. because it hits swap) and blocking VM 2? >> Good question. I haven't thought of this yet. But IIUC, >> the worker thread will complete VM1's job and then move on to >> executing VM2's scheduled work. >> It doesn't matter if VM1 is >> blocked currently. I think it would be a problem though if/when >> polling is introduced. > > Sorry, I wasn't clear. If VM1's memory is in swap, attempts to > access it might block the service thread, so it won't > complete VM2's job. Ah ok, I understand now. I am pretty sure the current RFC doesn't take care of this :) I will add this to my todo list for v2. Bandan > > >> >> >> >> >> #* Last run with the vCPU and I/O thread(s) pinned, no CPU/memory limit imposed. >> >> # I/O thread runs on CPU 14 or 15 depending on which guest it's serving >> >> >> >> There's a simple graph at >> >> http://people.redhat.com/~bdas/elvis/data/results.png >> >> that shows how task affinity results in a jump and even without it, >> >> as the number of guests increase, the shared vhost design performs >> >> slightly better. >> >> >> >> Observations: >> >> 1. In terms of "stock" performance, the results are comparable. >> >> 2. However, with a tuned setup, even without polling, we see an improvement >> >> with the new design. >> >> 3. Making the new design simulate old behavior would be a matter of setting >> >> the number of guests per vhost threads to 1. >> >> 4. Maybe, setting a per guest limit on the work being done by a specific vhost >> >> thread is needed for it to be fair. >> >> 5. cgroup associations needs to be figured out. I just slightly hacked the >> >> current cgroup association mechanism to work with the new model. Ccing cgroups >> >> for input/comments. >> >> >> >> Many thanks to Razya Ladelsky and Eyal Moscovici, IBM for the initial >> >> patches, the helpful testing suggestions and discussions. >> >> >> >> Bandan Das (4): >> >> vhost: Introduce a universal thread to serve all users >> >> vhost: Limit the number of devices served by a single worker thread >> >> cgroup: Introduce a function to compare cgroups >> >> vhost: Add cgroup-aware creation of worker threads >> >> >> >> drivers/vhost/net.c | 6 +- >> >> drivers/vhost/scsi.c | 18 ++-- >> >> drivers/vhost/vhost.c | 272 +++++++++++++++++++++++++++++++++++-------------- >> >> drivers/vhost/vhost.h | 32 +++++- >> >> include/linux/cgroup.h | 1 + >> >> kernel/cgroup.c | 40 ++++++++ >> >> 6 files changed, 275 insertions(+), 94 deletions(-) >> >> >> >> -- >> >> 2.4.3 -- To unsubscribe from this list: send the line "unsubscribe cgroups" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
