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1441242c35
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Fred Klassen 1441242c35 net/udp_gso: Allow TX timestamp with UDP GSO 
[ Upstream commit 76e21533a4 ]

Fixes an issue where TX Timestamps are not arriving on the error queue
when UDP_SEGMENT CMSG type is combined with CMSG type SO_TIMESTAMPING.
This can be illustrated with an updated updgso_bench_tx program which
includes the '-T' option to test for this condition. It also introduces
the '-P' option which will call poll() before reading the error queue.

    ./udpgso_bench_tx -4ucTPv -S 1472 -l2 -D 172.16.120.18
    poll timeout
    udp tx:      0 MB/s        1 calls/s      1 msg/s

The "poll timeout" message above indicates that TX timestamp never
arrived.

This patch preserves tx_flags for the first UDP GSO segment. Only the
first segment is timestamped, even though in some cases there may be
benefital in timestamping both the first and last segment.

Factors in deciding on first segment timestamp only:

- Timestamping both first and last segmented is not feasible. Hardware
can only have one outstanding TS request at a time.

- Timestamping last segment may under report network latency of the
previous segments. Even though the doorbell is suppressed, the ring
producer counter has been incremented.

- Timestamping the first segment has the upside in that it reports
timestamps from the application's view, e.g. RTT.

- Timestamping the first segment has the downside that it may
underreport tx host network latency. It appears that we have to pick
one or the other. And possibly follow-up with a config flag to choose
behavior.

v2: Remove tests as noted by Willem de Bruijn <willemb@google.com>
    Moving tests from net to net-next

v3: Update only relevant tx_flag bits as per
    Willem de Bruijn <willemb@google.com>

v4: Update comments and commit message as per
    Willem de Bruijn <willemb@google.com>

Fixes: ee80d1ebe5 ("udp: add udp gso")
Signed-off-by: Fred Klassen <fklassen@appneta.com>
Acked-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
2020-01-27 14:50:56 +01:00
arch powerpc/pseries/mobility: rebuild cacheinfo hierarchy post-migration 2020-01-27 14:50:55 +01:00
block block: don't use bio->bi_vcnt to figure out segment number 2020-01-27 14:50:23 +01:00
certs export.h: remove VMLINUX_SYMBOL() and VMLINUX_SYMBOL_STR() 2018-08-22 23:21:44 +09:00
crypto crypto: tgr192 - fix unaligned memory access 2020-01-27 14:50:13 +01:00
Documentation bus: ti-sysc: Add mcasp optional clocks flag 2020-01-27 14:50:02 +01:00
drivers drm/msm/mdp5: Fix mdp5_cfg_init error return 2020-01-27 14:50:56 +01:00
firmware Fix built-in early-load Intel microcode alignment 2020-01-23 08:21:29 +01:00
fs signal/cifs: Fix cifs_put_tcp_session to call send_sig instead of force_sig 2020-01-27 14:50:51 +01:00
include netfilter: nf_tables: correct NFT_LOGLEVEL_MAX value 2020-01-27 14:50:48 +01:00
init fork: fix some -Wmissing-prototypes warnings 2019-12-05 09:21:04 +01:00
ipc ipc/mqueue.c: only perform resource calculation if user valid 2019-08-06 19:06:52 +02:00
kernel kdb: do a sanity check on the cpu in kdb_per_cpu() 2020-01-27 14:50:48 +01:00
lib idr: Fix idr_get_next_ul race with idr_remove 2019-12-17 20:36:02 +01:00
LICENSES LICENSES: Remove CC-BY-SA-4.0 license text 2018-10-18 11:28:50 +02:00
mm mm/huge_memory.c: thp: fix conflict of above-47bit hint address and PMD alignment 2020-01-23 08:21:32 +01:00
net net/udp_gso: Allow TX timestamp with UDP GSO 2020-01-27 14:50:56 +01:00
samples samples: bpf: fix syscall_tp due to unused syscall 2020-01-12 12:17:13 +01:00
scripts kconfig: don't crash on NULL expressions in expr_eq() 2020-01-12 12:17:19 +01:00
security keys: Timestamp new keys 2020-01-27 14:50:23 +01:00
sound ASoC: meson: axg-tdmout: right_j is not supported 2020-01-27 14:50:55 +01:00
tools selftests/ipc: Fix msgque compiler warnings 2020-01-27 14:50:40 +01:00
usr kbuild: clean compressed initramfs image 2019-10-07 18:57:16 +02:00
virt KVM: arm/arm64: vgic: Don't rely on the wrong pending table 2019-12-13 08:52:45 +01:00
.clang-format clang-format: Set IndentWrappedFunctionNames false 2018-08-01 18:38:51 +02:00
.cocciconfig
.get_maintainer.ignore
.gitattributes .gitattributes: set git diff driver for C source code files 2016-10-07 18:46:30 -07:00
.gitignore Kbuild updates for v4.17 (2nd) 2018-04-15 17:21:30 -07:00
.mailmap libnvdimm-for-4.19_misc 2018-08-25 18:13:10 -07:00
COPYING COPYING: use the new text with points to the license files 2018-03-23 12:41:45 -06:00
CREDITS 9p: remove Ron Minnich from MAINTAINERS 2018-08-17 16:20:26 -07:00
Kbuild Kbuild updates for v4.15 2017-11-17 17:45:29 -08:00
Kconfig kconfig: move the "Executable file formats" menu to fs/Kconfig.binfmt 2018-08-02 08:06:55 +09:00
MAINTAINERS USB: rio500: Remove Rio 500 kernel driver 2019-10-17 13:44:47 -07:00
Makefile kbuild: mark prepare0 as PHONY to fix external module build 2020-01-27 14:50:13 +01:00
README Docs: Added a pointer to the formatted docs to README 2018-03-21 09:02:53 -06:00

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.