From: Tamas K Lengyel <tamas@tklengyel.com>
To: Petre Pircalabu <ppircalabu@bitdefender.com>
Cc: "Stefano Stabellini" <sstabellini@kernel.org>,
"Wei Liu" <wei.liu2@citrix.com>,
"Razvan Cojocaru" <rcojocaru@bitdefender.com>,
"Konrad Rzeszutek Wilk" <konrad.wilk@oracle.com>,
"George Dunlap" <George.Dunlap@eu.citrix.com>,
"Andrew Cooper" <andrew.cooper3@citrix.com>,
"Ian Jackson" <ian.jackson@eu.citrix.com>,
"Tim Deegan" <tim@xen.org>, "Julien Grall" <julien.grall@arm.com>,
"Jan Beulich" <jbeulich@suse.com>,
Xen-devel <xen-devel@lists.xenproject.org>,
"Roger Pau Monné" <roger.pau@citrix.com>
Subject: Re: [PATCH RFC 0/6] Slotted channels for sync vm_events
Date: Wed, 19 Dec 2018 15:33:05 -0700 [thread overview]
Message-ID: <CABfawhmPgmta2LPyMraKK2eLAqcdPrjUyox4dCGZD1MRx8wJDQ@mail.gmail.com> (raw)
In-Reply-To: <cover.1545245243.git.ppircalabu@bitdefender.com>
On Wed, Dec 19, 2018 at 11:52 AM Petre Pircalabu
<ppircalabu@bitdefender.com> wrote:
>
> This patchset is a rework of the "multi-page ring buffer" for vm_events
> patch based on Andrew Cooper's comments.
> For synchronous vm_events the ring waitqueue logic was unnecessary as the
> vcpu sending the request was blocked until a response was received.
> To simplify the request/response mechanism, an array of slotted channels
> was created, one per vcpu. Each vcpu puts the request in the
> corresponding slot and blocks until the response is received.
>
> I'm sending this patch as a RFC because, while I'm still working on way to
> measure the overall performance improvement, your feedback would be a great
> assistance.
Generally speaking this approach is OK, but I'm concerned that we will
eventually run into the same problem that brought up the idea of using
multi-page rings: vm_event structures that are larger then a page.
Right now this series adds a ring for each vCPU, which does mitigate
some of the bottleneck, but it does not really address the root cause.
It also adds significant complexity as the userspace side now has to
map in multiple rings, each with its own event channel and polling
requirements.
Tamas
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next prev parent reply other threads:[~2018-12-19 22:33 UTC|newest]
Thread overview: 50+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-12-19 18:52 [PATCH RFC 0/6] Slotted channels for sync vm_events Petre Pircalabu
2018-12-19 18:52 ` [RFC PATCH 1/6] tools/libxc: Consistent usage of xc_vm_event_* interface Petre Pircalabu
2018-12-19 18:52 ` [RFC PATCH 2/6] tools/libxc: Define VM_EVENT type Petre Pircalabu
2018-12-19 22:13 ` Tamas K Lengyel
2019-01-02 11:11 ` Wei Liu
2019-01-08 15:01 ` Petre Ovidiu PIRCALABU
2019-01-25 14:16 ` Wei Liu
2019-01-08 16:25 ` Jan Beulich
2019-02-11 12:30 ` Petre Ovidiu PIRCALABU
2018-12-19 18:52 ` [RFC PATCH 3/6] vm_event: Refactor vm_event_domain implementation Petre Pircalabu
2018-12-19 22:26 ` Tamas K Lengyel
2018-12-20 12:39 ` Petre Ovidiu PIRCALABU
2018-12-19 18:52 ` [RFC PATCH 4/6] vm_event: Use slotted channels for sync requests Petre Pircalabu
2018-12-20 12:05 ` Paul Durrant
2018-12-20 14:25 ` Petre Ovidiu PIRCALABU
2018-12-20 14:28 ` Paul Durrant
2018-12-20 15:03 ` Jan Beulich
2018-12-24 10:37 ` Julien Grall
2019-01-09 16:21 ` Razvan Cojocaru
2019-01-10 9:58 ` Paul Durrant
2019-01-10 15:28 ` Razvan Cojocaru
2019-01-08 14:49 ` Petre Ovidiu PIRCALABU
2019-01-08 15:08 ` Paul Durrant
2019-01-08 16:13 ` Petre Ovidiu PIRCALABU
2019-01-08 16:25 ` Paul Durrant
2019-01-10 15:30 ` Petre Ovidiu PIRCALABU
2019-01-10 15:46 ` Paul Durrant
2019-04-02 14:47 ` Andrew Cooper
2018-12-19 18:52 ` [RFC PATCH 5/6] xen-access: add support for slotted channel vm_events Petre Pircalabu
2018-12-19 18:52 ` [RFC PATCH 6/6] xc_version: add vm_event interface version Petre Pircalabu
2019-01-08 16:27 ` Jan Beulich
2019-01-08 16:37 ` Razvan Cojocaru
2019-01-08 16:47 ` Jan Beulich
2019-01-09 9:11 ` Razvan Cojocaru
2019-02-12 16:57 ` Petre Ovidiu PIRCALABU
2019-02-12 17:14 ` Jan Beulich
2019-02-12 18:13 ` Tamas K Lengyel
2019-02-12 18:19 ` Razvan Cojocaru
2019-02-12 18:25 ` Tamas K Lengyel
2018-12-19 22:33 ` Tamas K Lengyel [this message]
2018-12-19 23:30 ` [PATCH RFC 0/6] Slotted channels for sync vm_events Andrew Cooper
2018-12-20 10:48 ` Petre Ovidiu PIRCALABU
2018-12-20 14:08 ` Tamas K Lengyel
2019-02-06 14:26 ` Petre Ovidiu PIRCALABU
2019-02-07 11:46 ` George Dunlap
2019-02-07 16:06 ` Petre Ovidiu PIRCALABU
2019-02-12 17:01 ` Tamas K Lengyel
2019-02-19 11:48 ` Razvan Cojocaru
2019-03-04 16:01 ` George Dunlap
2019-03-04 16:20 ` Tamas K Lengyel
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