On 10/29/21 6:18 PM, Marek Marczykowski-Górecki wrote:
On Fri, Oct 29, 2021 at 05:46:18PM -0400, Boris Ostrovsky wrote:
On 10/29/21 10:20 AM, Juergen Gross wrote:
--- a/Documentation/ABI/stable/sysfs-devices-system-xen_memory +++ b/Documentation/ABI/stable/sysfs-devices-system-xen_memory @@ -84,3 +84,13 @@ Description: Control scrubbing pages before returning them to Xen for others domains use. Can be set with xen_scrub_pages cmdline parameter. Default value controlled with CONFIG_XEN_SCRUB_PAGES_DEFAULT.
+What: /sys/devices/system/xen_memory/xen_memory0/boot_timeout +Date: November 2021 +KernelVersion: 5.16 +Contact: xen-devel@lists.xenproject.org +Description:
The time (in seconds) to wait before giving up to boot in caseinitial ballooning fails to free enough memory. Applies onlywhen running as HVM or PVH guest and started with less memoryconfigured than allowed at max.How is this going to be used? We only need this during boot.
state = update_schedule(state);
balloon_state = update_schedule(balloon_state);Now that balloon_state has whole file scope it can probably be updated inside update_schedule().
- while ((credit = current_credit()) < 0) {
if (credit != last_credit) {last_changed = jiffies;last_credit = credit;}if (balloon_state == BP_ECANCELED) {What about other states? We are really waiting for BP_DONE, aren't we?
BP_DONE is set also as an intermediate step:
balloon_state = decrease_reservation(n_pages, GFP_BALLOON); if (balloon_state == BP_DONE && n_pages != -credit && n_pages < totalreserve_pages) balloon_state = BP_EAGAIN;It would be bad to finish waiting in this case.
RIght, but if we were to say 'if (balloon_state != BP_DONE)' the worst that can happen is that we will continue on to the next iteration without warning and/or panicing. Of course, there is a chance thaton the next iteration the same thing will happen but I think chances of hitting this race every time are infinitely low. We can also check for current_credit() again.
The question is whether we do want to continue waiting if we are in BP_AGAIN. I don't think BP_WAIT is possible in this case although this may change in the future and we will forget to update this code.
-boris