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Smith" , xen-devel@lists.xenproject.org References: <20260609151528.2426788-1-ross.lagerwall@citrix.com> <3034d82a-f1ae-4c6c-a293-ca44b7e086fc@suse.com> <552cac1b-2be9-481d-a687-01c965ade221@citrix.com> <683a3df4-21c7-434e-96c8-934631673795@citrix.com> Content-Language: en-US From: Jan Beulich Autocrypt: addr=jbeulich@suse.com; keydata= xsDiBFk3nEQRBADAEaSw6zC/EJkiwGPXbWtPxl2xCdSoeepS07jW8UgcHNurfHvUzogEq5xk hu507c3BarVjyWCJOylMNR98Yd8VqD9UfmX0Hb8/BrA+Hl6/DB/eqGptrf4BSRwcZQM32aZK 7Pj2XbGWIUrZrd70x1eAP9QE3P79Y2oLrsCgbZJfEwCgvz9JjGmQqQkRiTVzlZVCJYcyGGsD /0tbFCzD2h20ahe8rC1gbb3K3qk+LpBtvjBu1RY9drYk0NymiGbJWZgab6t1jM7sk2vuf0Py O9Hf9XBmK0uE9IgMaiCpc32XV9oASz6UJebwkX+zF2jG5I1BfnO9g7KlotcA/v5ClMjgo6Gl MDY4HxoSRu3i1cqqSDtVlt+AOVBJBACrZcnHAUSuCXBPy0jOlBhxPqRWv6ND4c9PH1xjQ3NP nxJuMBS8rnNg22uyfAgmBKNLpLgAGVRMZGaGoJObGf72s6TeIqKJo/LtggAS9qAUiuKVnygo 3wjfkS9A3DRO+SpU7JqWdsveeIQyeyEJ/8PTowmSQLakF+3fote9ybzd880fSmFuIEJldWxp Y2ggPGpiZXVsaWNoQHN1c2UuY29tPsJgBBMRAgAgBQJZN5xEAhsDBgsJCAcDAgQVAggDBBYC AwECHgECF4AACgkQoDSui/t3IH4J+wCfQ5jHdEjCRHj23O/5ttg9r9OIruwAn3103WUITZee e7Sbg12UgcQ5lv7SzsFNBFk3nEQQCACCuTjCjFOUdi5Nm244F+78kLghRcin/awv+IrTcIWF hUpSs1Y91iQQ7KItirz5uwCPlwejSJDQJLIS+QtJHaXDXeV6NI0Uef1hP20+y8qydDiVkv6l IreXjTb7DvksRgJNvCkWtYnlS3mYvQ9NzS9PhyALWbXnH6sIJd2O9lKS1Mrfq+y0IXCP10eS FFGg+Av3IQeFatkJAyju0PPthyTqxSI4lZYuJVPknzgaeuJv/2NccrPvmeDg6Coe7ZIeQ8Yj t0ARxu2xytAkkLCel1Lz1WLmwLstV30g80nkgZf/wr+/BXJW/oIvRlonUkxv+IbBM3dX2OV8 AmRv1ySWPTP7AAMFB/9PQK/VtlNUJvg8GXj9ootzrteGfVZVVT4XBJkfwBcpC/XcPzldjv+3 HYudvpdNK3lLujXeA5fLOH+Z/G9WBc5pFVSMocI71I8bT8lIAzreg0WvkWg5V2WZsUMlnDL9 mpwIGFhlbM3gfDMs7MPMu8YQRFVdUvtSpaAs8OFfGQ0ia3LGZcjA6Ik2+xcqscEJzNH+qh8V m5jjp28yZgaqTaRbg3M/+MTbMpicpZuqF4rnB0AQD12/3BNWDR6bmh+EkYSMcEIpQmBM51qM EKYTQGybRCjpnKHGOxG0rfFY1085mBDZCH5Kx0cl0HVJuQKC+dV2ZY5AqjcKwAxpE75MLFkr wkkEGBECAAkFAlk3nEQCGwwACgkQoDSui/t3IH7nnwCfcJWUDUFKdCsBH/E5d+0ZnMQi+G0A nAuWpQkjM1ASeQwSHEeAWPgskBQL In-Reply-To: <683a3df4-21c7-434e-96c8-934631673795@citrix.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-purgate-ID: tlsNG-d25034/1781523253-F5386CF5-993F7128/0/0 X-purgate-type: clean X-purgate-size: 1607 On 15.06.2026 13:17, Ross Lagerwall wrote: > On 6/11/26 5:06 PM, Jan Beulich wrote: >> On 11.06.2026 18:02, Ross Lagerwall wrote: >>> On 6/11/26 3:55 PM, Jan Beulich wrote: >>>> On 09.06.2026 17:15, Ross Lagerwall wrote: >>>>> When performing multiple migrations in parallel, the domctl lock may >>>>> become extremely contended: >>>>> >>>>> * Operations like "xl vcpu-list" were observed to take in excess of 20s >>>>> to execute. >>>> >>>> Does "xl vcpu-list" involve ... >>>> >>>>> * The "clean" shadow op may pause the domain, restart with a >>>>> continuation and then become blocked on the domctl lock, causing VM >>>>> downtime in excess of 20 seconds. >>>>> >>>>> These issues can be fixed by not holding the domctl for the frequently >>>>> called operations during migration. >>>>> >>>>> Thanks >>>>> >>>>> Ross Lagerwall (2): >>>>> domctl: Handle XEN_DOMCTL_getpageframeinfo3 without the domctl lock >>>> >>>> ... XEN_DOMCTL_getpageframeinfo3? >>>> >>> >>> No, but "xl vcpu-list" takes the domctl lock >> >> If this is still the case after XSA-492, then maybe the follow-ups I have >> pending to post will eliminate (or at least reduce) this. I don't think >> that's 4.22 material, though. > > Yes, AFAICT "xl vcpu-list" calls XEN_DOMCTL_getvcpuinfo and > XEN_DOMCTL_getvcpuaffinity for each domain and both of these still take > the domctl lock. XEN_DOMCTL_getvcpuinfo is taken care of by my to-be-posted follow-on. XEN_DOMCTL_[gs]etvcpuaffinity first need to have their own locking added, before their handling can be moved out. Jan