From: Oleksandr <olekstysh@gmail.com>
To: paul@xen.org
Cc: 'Jan Beulich' <jbeulich@suse.com>,
'Oleksandr Tyshchenko' <oleksandr_tyshchenko@epam.com>,
'Stefano Stabellini' <sstabellini@kernel.org>,
'Julien Grall' <julien@xen.org>,
'Volodymyr Babchuk' <Volodymyr_Babchuk@epam.com>,
'Andrew Cooper' <andrew.cooper3@citrix.com>,
'George Dunlap' <george.dunlap@citrix.com>,
'Ian Jackson' <iwj@xenproject.org>, 'Wei Liu' <wl@xen.org>,
'Julien Grall' <julien.grall@arm.com>,
xen-devel@lists.xenproject.org
Subject: Re: [PATCH V3 17/23] xen/ioreq: Introduce domain_has_ioreq_server()
Date: Thu, 10 Dec 2020 18:57:44 +0200 [thread overview]
Message-ID: <1c012758-7121-5702-038e-4510f3cf1b0b@gmail.com> (raw)
In-Reply-To: <002401d6cecf$ce472710$6ad57530$@xen.org>
On 10.12.20 10:38, Paul Durrant wrote:
Hi Paul.
>> -----Original Message-----
>> From: Oleksandr <olekstysh@gmail.com>
>> Sent: 09 December 2020 20:36
>> To: paul@xen.org
>> Cc: 'Jan Beulich' <jbeulich@suse.com>; 'Oleksandr Tyshchenko' <oleksandr_tyshchenko@epam.com>;
>> 'Stefano Stabellini' <sstabellini@kernel.org>; 'Julien Grall' <julien@xen.org>; 'Volodymyr Babchuk'
>> <Volodymyr_Babchuk@epam.com>; 'Andrew Cooper' <andrew.cooper3@citrix.com>; 'George Dunlap'
>> <george.dunlap@citrix.com>; 'Ian Jackson' <iwj@xenproject.org>; 'Wei Liu' <wl@xen.org>; 'Julien Grall'
>> <julien.grall@arm.com>; xen-devel@lists.xenproject.org
>> Subject: Re: [PATCH V3 17/23] xen/ioreq: Introduce domain_has_ioreq_server()
>>
>>
>> Hi Paul.
>>
>>
>>>>>>>> On 30.11.2020 11:31, Oleksandr Tyshchenko wrote:
>>>>>>>>> --- a/xen/include/xen/ioreq.h
>>>>>>>>> +++ b/xen/include/xen/ioreq.h
>>>>>>>>> @@ -55,6 +55,20 @@ struct ioreq_server {
>>>>>>>>> uint8_t bufioreq_handling;
>>>>>>>>> };
>>>>>>>>> +/*
>>>>>>>>> + * This should only be used when d == current->domain and it's not
>>>>>>>>> paused,
>>>>>>>> Is the "not paused" part really relevant here? Besides it being rare
>>>>>>>> that the current domain would be paused (if so, it's in the process
>>>>>>>> of having all its vCPU-s scheduled out), does this matter at all?do
>>>>>>>> any extra actionsdo any extra actions
>>>>>>> No, it isn't relevant, I will drop it.
>>>>>>>
>>>>>>>
>>>>>>>> Apart from this the patch looks okay to me, but I'm not sure it
>>>>>>>> addresses Paul's concerns. Iirc he had suggested to switch back to
>>>>>>>> a list if doing a swipe over the entire array is too expensive in
>>>>>>>> this specific case.
>>>>>>> We would like to avoid to do any extra actions in
>>>>>>> leave_hypervisor_to_guest() if possible.
>>>>>>> But not only there, the logic whether we check/set
>>>>>>> mapcache_invalidation variable could be avoided if a domain doesn't
>>>>>>> use IOREQ server...
>>>>>> Are you OK with this patch (common part of it)?
>>>>> How much of a performance benefit is this? The array is small to simply counting the non-NULL
>>>> entries should be pretty quick.
>>>> I didn't perform performance measurements on how much this call consumes.
>>>> In our system we run three domains. The emulator is in DomD only, so I
>>>> would like to avoid to call vcpu_ioreq_handle_completion() for every
>>>> Dom0/DomU's vCPUs
>>>> if there is no real need to do it.
>>> This is not relevant to the domain that the emulator is running in; it's concerning the domains
>> which the emulator is servicing. How many of those are there?
>> Err, yes, I wasn't precise when providing an example.
>> Single emulator is running in DomD and servicing DomU. So with the
>> helper in place the vcpu_ioreq_handle_completion() gets only called for
>> DomU vCPUs (as expected).
>> Without an optimization the vcpu_ioreq_handle_completion() gets called
>> for _all_ vCPUs, and I see it as an extra action for Dom0, DomD vCPUs.
>>
>>
>>>> On Arm vcpu_ioreq_handle_completion()
>>>> is called with IRQ enabled, so the call is accompanied with
>>>> corresponding irq_enable/irq_disable.
>>>> These unneeded actions could be avoided by using this simple one-line
>>>> helper...
>>>>
>>> The helper may be one line but there is more to the patch than that. I still think you could just
>> walk the array in the helper rather than keeping a running occupancy count.
>>
>> OK, is the implementation below close to what you propose? If yes, I
>> will update a helper and drop nr_servers variable.
>>
>> bool domain_has_ioreq_server(const struct domain *d)
>> {
>> const struct ioreq_server *s;
>> unsigned int id;
>>
>> FOR_EACH_IOREQ_SERVER(d, id, s)
>> return true;
>>
>> return false;
>> }
> Yes, that's what I had in mind.
>
> Paul
Thank you for the clarification.
--
Regards,
Oleksandr Tyshchenko
next prev parent reply other threads:[~2020-12-10 16:57 UTC|newest]
Thread overview: 127+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-30 10:31 Oleksandr Tyshchenko
2020-11-30 10:31 ` [PATCH V3 01/23] x86/ioreq: Prepare IOREQ feature for making it common Oleksandr Tyshchenko
2020-12-01 11:03 ` Alex Bennée
2020-12-01 18:53 ` Oleksandr
2020-12-01 19:36 ` Alex Bennée
2020-12-02 8:00 ` Jan Beulich
2020-12-02 11:19 ` Oleksandr
2020-12-07 11:13 ` Jan Beulich
2020-12-07 15:27 ` Oleksandr
2020-12-07 16:29 ` Jan Beulich
2020-12-07 17:21 ` Oleksandr
2020-11-30 10:31 ` [PATCH V3 02/23] x86/ioreq: Add IOREQ_STATUS_* #define-s and update code for moving Oleksandr Tyshchenko
2020-12-01 11:07 ` Alex Bennée
2020-12-07 11:19 ` Jan Beulich
2020-12-07 15:37 ` Oleksandr
2020-11-30 10:31 ` [PATCH V3 03/23] x86/ioreq: Provide out-of-line wrapper for the handle_mmio() Oleksandr Tyshchenko
2020-12-07 11:27 ` Jan Beulich
2020-12-07 15:39 ` Oleksandr
2020-11-30 10:31 ` [PATCH V3 04/23] xen/ioreq: Make x86's IOREQ feature common Oleksandr Tyshchenko
2020-12-07 11:41 ` Jan Beulich
2020-12-07 19:43 ` Oleksandr
2020-12-08 9:21 ` Jan Beulich
2020-12-08 13:56 ` Oleksandr
2020-12-08 15:02 ` Jan Beulich
2020-12-08 17:24 ` Oleksandr
2020-11-30 10:31 ` [PATCH V3 05/23] xen/ioreq: Make x86's hvm_ioreq_needs_completion() common Oleksandr Tyshchenko
2020-12-07 11:47 ` Jan Beulich
2020-11-30 10:31 ` [PATCH V3 06/23] xen/ioreq: Make x86's hvm_mmio_first(last)_byte() common Oleksandr Tyshchenko
2020-12-07 11:48 ` Jan Beulich
2020-11-30 10:31 ` [PATCH V3 07/23] xen/ioreq: Make x86's hvm_ioreq_(page/vcpu/server) structs common Oleksandr Tyshchenko
2020-12-07 11:54 ` Jan Beulich
2020-11-30 10:31 ` [PATCH V3 08/23] xen/ioreq: Move x86's ioreq_server to struct domain Oleksandr Tyshchenko
2020-12-07 12:04 ` Jan Beulich
2020-12-07 12:12 ` Paul Durrant
2020-12-07 19:52 ` Oleksandr
2020-11-30 10:31 ` [PATCH V3 09/23] xen/dm: Make x86's DM feature common Oleksandr Tyshchenko
2020-12-07 12:08 ` Jan Beulich
2020-12-07 20:23 ` Oleksandr
2020-12-08 9:30 ` Jan Beulich
2020-12-08 14:54 ` Oleksandr
2021-01-07 14:38 ` Oleksandr
2021-01-07 15:01 ` Jan Beulich
2021-01-07 16:49 ` Oleksandr
2021-01-12 22:23 ` Oleksandr
2020-11-30 10:31 ` [PATCH V3 10/23] xen/mm: Make x86's XENMEM_resource_ioreq_server handling common Oleksandr Tyshchenko
2020-12-07 11:35 ` Jan Beulich
2020-12-07 12:11 ` Jan Beulich
2020-12-07 21:06 ` Oleksandr
2020-11-30 10:31 ` [PATCH V3 11/23] xen/ioreq: Move x86's io_completion/io_req fields to struct vcpu Oleksandr Tyshchenko
2020-12-07 12:32 ` Jan Beulich
2020-12-07 20:59 ` Oleksandr
2020-12-08 7:52 ` Paul Durrant
2020-12-08 9:35 ` Jan Beulich
2020-12-08 18:21 ` Oleksandr
2020-11-30 10:31 ` [PATCH V3 12/23] xen/ioreq: Remove "hvm" prefixes from involved function names Oleksandr Tyshchenko
2020-12-07 12:45 ` Jan Beulich
2020-12-07 20:28 ` Oleksandr
2020-11-30 10:31 ` [PATCH V3 13/23] xen/ioreq: Use guest_cmpxchg64() instead of cmpxchg() Oleksandr Tyshchenko
2020-12-09 21:32 ` Stefano Stabellini
2020-12-09 22:34 ` Oleksandr
2020-12-10 2:30 ` Stefano Stabellini
2020-11-30 10:31 ` [PATCH V3 14/23] arm/ioreq: Introduce arch specific bits for IOREQ/DM features Oleksandr Tyshchenko
2020-12-09 22:04 ` Stefano Stabellini
2020-12-09 22:49 ` Oleksandr
2020-12-10 2:30 ` Stefano Stabellini
2020-11-30 10:31 ` [PATCH V3 15/23] xen/arm: Stick around in leave_hypervisor_to_guest until I/O has completed Oleksandr Tyshchenko
2020-11-30 20:51 ` Volodymyr Babchuk
2020-12-01 12:46 ` Julien Grall
2020-12-09 23:18 ` Stefano Stabellini
2020-12-09 23:35 ` Stefano Stabellini
2020-12-09 23:47 ` Julien Grall
2020-12-10 2:30 ` Stefano Stabellini
2020-12-10 13:17 ` Julien Grall
2020-12-10 13:21 ` Oleksandr
2020-12-09 23:38 ` Julien Grall
2020-11-30 10:31 ` [PATCH V3 16/23] xen/mm: Handle properly reference in set_foreign_p2m_entry() on Arm Oleksandr Tyshchenko
2020-12-08 14:24 ` Jan Beulich
2020-12-08 16:41 ` Oleksandr
2020-12-09 23:49 ` Stefano Stabellini
2021-01-15 1:18 ` Stefano Stabellini
2020-11-30 10:31 ` [PATCH V3 17/23] xen/ioreq: Introduce domain_has_ioreq_server() Oleksandr Tyshchenko
2020-12-08 15:11 ` Jan Beulich
2020-12-08 15:33 ` Oleksandr
2020-12-08 16:56 ` Oleksandr
2020-12-08 19:43 ` Paul Durrant
2020-12-08 20:16 ` Oleksandr
2020-12-09 9:01 ` Paul Durrant
2020-12-09 18:58 ` Julien Grall
2020-12-09 21:05 ` Oleksandr
2020-12-09 20:36 ` Oleksandr
2020-12-10 8:38 ` Paul Durrant
2020-12-10 16:57 ` Oleksandr [this message]
2020-11-30 10:31 ` [PATCH V3 18/23] xen/dm: Introduce xendevicemodel_set_irq_level DM op Oleksandr Tyshchenko
2020-12-10 2:21 ` Stefano Stabellini
2020-12-10 12:58 ` Oleksandr
2020-12-10 13:38 ` Julien Grall
2020-11-30 10:31 ` [PATCH V3 19/23] xen/arm: io: Abstract sign-extension Oleksandr Tyshchenko
2020-11-30 21:03 ` Volodymyr Babchuk
2020-11-30 23:27 ` Oleksandr
2020-12-01 7:55 ` Jan Beulich
2020-12-01 10:30 ` Julien Grall
2020-12-01 10:42 ` Oleksandr
2020-12-01 12:13 ` Julien Grall
2020-12-01 12:24 ` Oleksandr
2020-12-01 12:28 ` Julien Grall
2020-12-01 10:49 ` Jan Beulich
2020-12-01 10:23 ` Julien Grall
2020-11-30 10:31 ` [PATCH V3 20/23] xen/ioreq: Make x86's send_invalidate_req() common Oleksandr Tyshchenko
2020-12-08 15:24 ` Jan Beulich
2020-12-08 16:49 ` Oleksandr
2020-12-09 8:21 ` Jan Beulich
2020-11-30 10:31 ` [PATCH V3 21/23] xen/arm: Add mapcache invalidation handling Oleksandr Tyshchenko
2020-12-10 2:30 ` Stefano Stabellini
2020-12-10 18:50 ` Julien Grall
2020-12-11 1:28 ` Stefano Stabellini
2020-12-11 11:21 ` Oleksandr
2020-12-11 19:07 ` Stefano Stabellini
2020-12-11 19:37 ` Julien Grall
2020-12-11 19:27 ` Julien Grall
2020-11-30 10:31 ` [PATCH V3 22/23] libxl: Introduce basic virtio-mmio support on Arm Oleksandr Tyshchenko
2020-11-30 10:31 ` [PATCH V3 23/23] [RFC] libxl: Add support for virtio-disk configuration Oleksandr Tyshchenko
2020-11-30 11:22 ` [PATCH V3 00/23] IOREQ feature (+ virtio-mmio) on Arm Oleksandr
2020-12-07 13:03 ` Wei Chen
2020-12-07 21:03 ` Oleksandr
2020-11-30 16:21 ` Alex Bennée
2020-11-30 22:22 ` [PATCH V3 00/23] IOREQ feature (+ virtio-mmio) on Arm Oleksandr
2020-12-29 15:32 ` Roger Pau Monné
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