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From bd86e4e5fd283179e97ef07354d822afbf21b7dd Mon Sep 17 00:00:00 2001
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Message-Id: <bd86e4e5fd283179e97ef07354d822afbf21b7dd.1387382496.git.minovotn@redhat.com>
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In-Reply-To: <c5386144fbf09f628148101bc674e2421cdd16e3.1387382496.git.minovotn@redhat.com>
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References: <c5386144fbf09f628148101bc674e2421cdd16e3.1387382496.git.minovotn@redhat.com>
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From: Nigel Croxon <ncroxon@redhat.com>
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Date: Thu, 14 Nov 2013 22:52:48 +0100
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Subject: [PATCH 12/46] rdma: update documentation to reflect new unpin
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 support
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RH-Author: Nigel Croxon <ncroxon@redhat.com>
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Message-id: <1384469598-13137-13-git-send-email-ncroxon@redhat.com>
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Patchwork-id: 55702
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O-Subject: [RHEL7.0 PATCH 12/42] rdma: update documentation to reflect new unpin support
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Bugzilla: 1011720
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RH-Acked-by: Orit Wasserman <owasserm@redhat.com>
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RH-Acked-by: Amit Shah <amit.shah@redhat.com>
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RH-Acked-by: Paolo Bonzini <pbonzini@redhat.com>
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Bugzilla: 1011720
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https://bugzilla.redhat.com/show_bug.cgi?id=1011720
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>From commit ID:
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commit a5f56b906e0d7975b87dc3d3c5bfe5a75a4028d2
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Author: Michael R. Hines <mrhines@us.ibm.com>
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Date:   Mon Jul 22 10:01:51 2013 -0400
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    rdma: update documentation to reflect new unpin support
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    As requested, the protocol now includes memory unpinning support.
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    This has been implemented in a non-optimized manner, in such a way
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    that one could devise an LRU or other workload-specific information
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    on top of the basic mechanism to influence the way unpinning happens
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    during runtime.
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    The feature is not yet user-facing, and is thus can only be enabled
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    at compile-time.
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    Reviewed-by: Eric Blake <eblake@redhat.com>
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    Signed-off-by: Michael R. Hines <mrhines@us.ibm.com>
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    Signed-off-by: Juan Quintela <quintela@redhat.com>
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---
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 docs/rdma.txt |   51 ++++++++++++++++++++++++++++++---------------------
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 1 files changed, 30 insertions(+), 21 deletions(-)
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Signed-off-by: Michal Novotny <minovotn@redhat.com>
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---
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 docs/rdma.txt | 51 ++++++++++++++++++++++++++++++---------------------
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 1 file changed, 30 insertions(+), 21 deletions(-)
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diff --git a/docs/rdma.txt b/docs/rdma.txt
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index 45a4b1d..45d1c8a 100644
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--- a/docs/rdma.txt
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+++ b/docs/rdma.txt
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@@ -35,7 +35,7 @@ memory tracked during each live migration iteration round cannot keep pace
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 with the rate of dirty memory produced by the workload.
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 RDMA currently comes in two flavors: both Ethernet based (RoCE, or RDMA
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-over Convered Ethernet) as well as Infiniband-based. This implementation of
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+over Converged Ethernet) as well as Infiniband-based. This implementation of
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 migration using RDMA is capable of using both technologies because of
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 the use of the OpenFabrics OFED software stack that abstracts out the
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 programming model irrespective of the underlying hardware.
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@@ -188,9 +188,9 @@ header portion and a data portion (but together are transmitted
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 as a single SEND message).
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 Header:
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-    * Length  (of the data portion, uint32, network byte order)
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-    * Type    (what command to perform, uint32, network byte order)
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-    * Repeat  (Number of commands in data portion, same type only)
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+    * Length               (of the data portion, uint32, network byte order)
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+    * Type                 (what command to perform, uint32, network byte order)
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+    * Repeat               (Number of commands in data portion, same type only)
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 The 'Repeat' field is here to support future multiple page registrations
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 in a single message without any need to change the protocol itself
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@@ -202,17 +202,19 @@ The maximum number of repeats is hard-coded to 4096. This is a conservative
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 limit based on the maximum size of a SEND message along with emperical
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 observations on the maximum future benefit of simultaneous page registrations.
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-The 'type' field has 10 different command values:
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-    1. Unused
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-    2. Error              (sent to the source during bad things)
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-    3. Ready              (control-channel is available)
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-    4. QEMU File          (for sending non-live device state)
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-    5. RAM Blocks request (used right after connection setup)
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-    6. RAM Blocks result  (used right after connection setup)
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-    7. Compress page      (zap zero page and skip registration)
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-    8. Register request   (dynamic chunk registration)
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-    9. Register result    ('rkey' to be used by sender)
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-    10. Register finished  (registration for current iteration finished)
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+The 'type' field has 12 different command values:
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+     1. Unused
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+     2. Error                      (sent to the source during bad things)
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+     3. Ready                      (control-channel is available)
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+     4. QEMU File                  (for sending non-live device state)
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+     5. RAM Blocks request         (used right after connection setup)
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+     6. RAM Blocks result          (used right after connection setup)
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+     7. Compress page              (zap zero page and skip registration)
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+     8. Register request           (dynamic chunk registration)
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+     9. Register result            ('rkey' to be used by sender)
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+    10. Register finished          (registration for current iteration finished)
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+    11. Unregister request         (unpin previously registered memory)
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+    12. Unregister finished        (confirmation that unpin completed)
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 A single control message, as hinted above, can contain within the data
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 portion an array of many commands of the same type. If there is more than
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@@ -243,7 +245,7 @@ qemu_rdma_exchange_send(header, data, optional response header & data):
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    from the receiver to tell us that the receiver
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    is *ready* for us to transmit some new bytes.
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 2. Optionally: if we are expecting a response from the command
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-   (that we have no yet transmitted), let's post an RQ
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+   (that we have not yet transmitted), let's post an RQ
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    work request to receive that data a few moments later.
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 3. When the READY arrives, librdmacm will
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    unblock us and we immediately post a RQ work request
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@@ -293,8 +295,10 @@ librdmacm provides the user with a 'private data' area to be exchanged
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 at connection-setup time before any infiniband traffic is generated.
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 Header:
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-    * Version (protocol version validated before send/recv occurs), uint32, network byte order
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-    * Flags   (bitwise OR of each capability), uint32, network byte order
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+    * Version (protocol version validated before send/recv occurs),
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+                                               uint32, network byte order
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+    * Flags   (bitwise OR of each capability),
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+                                               uint32, network byte order
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 There is no data portion of this header right now, so there is
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 no length field. The maximum size of the 'private data' section
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@@ -313,7 +317,7 @@ If the version is invalid, we throw an error.
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 If the version is new, we only negotiate the capabilities that the
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 requested version is able to perform and ignore the rest.
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-Currently there is only *one* capability in Version #1: dynamic page registration
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+Currently there is only one capability in Version #1: dynamic page registration
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 Finally: Negotiation happens with the Flags field: If the primary-VM
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 sets a flag, but the destination does not support this capability, it
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@@ -326,8 +330,8 @@ QEMUFileRDMA Interface:
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 QEMUFileRDMA introduces a couple of new functions:
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-1. qemu_rdma_get_buffer()  (QEMUFileOps rdma_read_ops)
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-2. qemu_rdma_put_buffer()  (QEMUFileOps rdma_write_ops)
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+1. qemu_rdma_get_buffer()               (QEMUFileOps rdma_read_ops)
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+2. qemu_rdma_put_buffer()               (QEMUFileOps rdma_write_ops)
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 These two functions are very short and simply use the protocol
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 describe above to deliver bytes without changing the upper-level
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@@ -413,3 +417,8 @@ TODO:
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    the use of KSM and ballooning while using RDMA.
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 4. Also, some form of balloon-device usage tracking would also
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    help alleviate some issues.
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+5. Move UNREGISTER requests to a separate thread.
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+6. Use LRU to provide more fine-grained direction of UNREGISTER
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+   requests for unpinning memory in an overcommitted environment.
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+7. Expose UNREGISTER support to the user by way of workload-specific
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+   hints about application behavior.
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-- 
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1.7.11.7
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