[Pkg-xen-devel] Bug#880554: Bug#880554: #880554: max grant frames problem

[Hans van Kranenburg]

On 7/18/19 1:30 AM, Hans van Kranenburg wrote:
> Hi,
> 
> On 10/23/18 7:34 PM, Ian Jackson wrote:
>> Control: retitle -1 max grant frames problem (domu freeze with linux-image-4.9.0-4-amd64)
>> Control: severity -1 important
>> Control: reassign -1 src:xen 4.8.3+xsa267+shim4.10.1+xsa267-1+deb9u9
> 
> my last comment in this bts bug was about:
> 
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=29d11cfd8698038b87458ba4d1329b9da81150a5
> 
> ..which is in since linux 4.13-rc2, and buster has 4.19+
> 
> Is there anyone who would wants to try reproduce the max grant frames
> problem on buster with Xen 4.11 and Linux 4.19 dom0/domU?
> 
> The 'xen/grant-table: max_grant_frames reached' should show up on the
> serial console. I'd like to see a test report of it actually happening.

I actually just did this, by putting max_grant_frames = 4 in a domU
config file and starting it (Linux 4.19 domU on Xen 4.11):

Welcome to Debian GNU/Linux 10 (buster)!

[    5.499058] systemd[1]: Set hostname to <debug-btrfs-buster>.
[    5.552968] xen:grant_table: xen/grant-table: max_grant_frames
reached cur=4 extra=1 limit=4 gnttab_free_count=3 req_entries=1
[    5.554012] xen:grant_table: xen/grant-table: max_grant_frames
reached cur=4 extra=1 limit=4 gnttab_free_count=3 req_entries=1
[    5.555858] xen:grant_table: xen/grant-table: max_grant_frames
reached cur=4 extra=1 limit=4 gnttab_free_count=3 req_entries=1
[    5.556950] xen:grant_table: xen/grant-table: max_grant_frames
reached cur=4 extra=1 limit=4 gnttab_free_count=3 req_entries=1
[    5.557082] xen:grant_table: xen/grant-table: max_grant_frames
reached cur=4 extra=1 limit=4 gnttab_free_count=3 req_entries=1
[    5.557295] xen:grant_table: xen/grant-table: max_grant_frames
reached cur=4 extra=1 limit=4 gnttab_free_count=3 req_entries=1
[    5.557636] xen:grant_table: xen/grant-table: max_grant_frames
reached cur=4 extra=1 limit=4 gnttab_free_count=3 req_entries=1
[    5.558960] xen:grant_table: xen/grant-table: max_grant_frames
reached cur=4 extra=1 limit=4 gnttab_free_count=3 req_entries=1
[    5.559800] xen:grant_table: xen/grant-table: max_grant_frames
reached cur=4 extra=1 limit=4 gnttab_free_count=3 req_entries=1
[    6.014291] gnttab_expand: 159 callbacks suppressed
[    6.014296] xen:grant_table: xen/grant-table: max_grant_frames
reached cur=4 extra=1 limit=4 gnttab_free_count=0 req_entries=3
[    6.014351] xen:grant_table: xen/grant-table: max_grant_frames
reached cur=4 extra=1 limit=4 gnttab_free_count=0 req_entries=8
[    6.033683] xen:grant_table: xen/grant-table: max_grant_frames
reached cur=4 extra=1 limit=4 gnttab_free_count=0 req_entries=3
[    6.055013] xen:grant_table: xen/grant-table: max_grant_frames
reached cur=4 extra=1 limit=4 gnttab_free_count=0 req_entries=3
[    6.055729] xen:grant_table: xen/grant-table: max_grant_frames
reached cur=4 extra=1 limit=4 gnttab_free_count=0 req_entries=26
[    6.060256] xen:grant_table: xen/grant-table: max_grant_frames
reached cur=4 extra=1 limit=4 gnttab_free_count=0 req_entries=3
[    6.077000] xen:grant_table: xen/grant-table: max_grant_frames
reached cur=4 extra=1 limit=4 gnttab_free_count=0 req_entries=3
[    6.109760] xen:grant_table: xen/grant-table: max_grant_frames
reached cur=4 extra=1 limit=4 gnttab_free_count=0 req_entries=3
[    6.138126] xen:grant_table: xen/grant-table: max_grant_frames
reached cur=4 extra=1 limit=4 gnttab_free_count=0 req_entries=3
[    6.148626] xen:grant_table: xen/grant-table: max_grant_frames
reached cur=4 extra=1 limit=4 gnttab_free_count=0 req_entries=3

Yay. Better info for the users!

Also, there's a patch in review that can improve the situation:

https://lists.xenproject.org/archives/html/xen-devel/2019-11/msg01607.html

The biggest annoyance in our Xen 4.11 now is that the default value for
the hypervisor command line of gnttab_max_frames is raised to 64 from 32
a while ago, but the toolstack overwrites this again with a default of
32. The patch attempts to fix that.

Hans