On 7/15/2020 8:21 AM, Van Haaren, Harry wrote:
-----Original Message-----
From: Ilya Maximets <i.maxim...@ovn.org>
Sent: Wednesday, July 15, 2020 2:28 PM
To: Van Haaren, Harry <harry.van.haa...@intel.com>; Ilya Maximets
<i.maxim...@ovn.org>; William Tu <u9012...@gmail.com>; Gregory Rose
<gvrose8...@gmail.com>; Stokes, Ian <ian.sto...@intel.com>
Cc: d...@openvswitch.org
Subject: Re: [PATCH] rpm-fedora: Add missing dist library
On 7/15/20 2:36 PM, Van Haaren, Harry wrote:
-----Original Message-----
From: Ilya Maximets <i.maxim...@ovn.org>
Sent: Wednesday, July 15, 2020 1:22 PM
To: Van Haaren, Harry <harry.van.haa...@intel.com>; Ilya Maximets
<i.maxim...@ovn.org>; William Tu <u9012...@gmail.com>; Gregory Rose
<gvrose8...@gmail.com>; Stokes, Ian <ian.sto...@intel.com>
Cc: d...@openvswitch.org
Subject: Re: [PATCH] rpm-fedora: Add missing dist library
On 7/15/20 1:45 PM, Van Haaren, Harry wrote:
-----Original Message-----
From: Ilya Maximets <i.maxim...@ovn.org>
Sent: Wednesday, July 15, 2020 10:16 AM
To: William Tu <u9012...@gmail.com>; Gregory Rose
<gvrose8...@gmail.com>;
Van Haaren, Harry <harry.van.haa...@intel.com>; Stokes, Ian
<ian.sto...@intel.com>
Cc: d...@openvswitch.org; Ilya Maximets <i.maxim...@ovn.org>;
i.maxim...@ovn.org
Subject: Re: [PATCH] rpm-fedora: Add missing dist library
On 7/15/20 1:33 AM, William Tu wrote:
On Tue, Jul 14, 2020 at 03:40:39PM -0700, Gregory Rose wrote:
On 7/14/2020 1:49 PM, Greg Rose wrote:
libopenvswitchavx512.a is needed for the fedora rpm spec.
Signed-off-by: Greg Rose <gvrose8...@gmail.com>
---
rhel/openvswitch-fedora.spec.in | 1 +
1 file changed, 1 insertion(+)
diff --git a/rhel/openvswitch-fedora.spec.in b/rhel/openvswitch-
fedora.spec.in
index 7bc8c34..154b49e 100644
--- a/rhel/openvswitch-fedora.spec.in
+++ b/rhel/openvswitch-fedora.spec.in
@@ -457,6 +457,7 @@ fi
%{_bindir}/ovs-pki
%{_bindir}/vtep-ctl
%{_libdir}/lib*.so.*
+%{_libdir}/libopenvswitchavx512.a
How come before the avx512 patch series, we don't need to put
libopenvswitch.a here?
And now we need to add libopenvswitchavx512.a?
Do we need to also add other .a files such as libsflow.a, libopenvswitch.a?
It seems like the real issue is that rpm build requests to build shared
libraries only, but we're building this static library for some reason.
We should not include it into the package. I think, we need to fix the
build process and avoid building it in a first place.
Hey folks!
As you know the AVX512 patchset enables CPU ISA detection. ISA detection
and building is a little more complex, and indeed this is the first time that it
is being done in OVS - so we're all on a learning curve here.
OVS supports an --enable-shared build mode, where OVS itself is built as a
shared object. When this is enabled, components in OVS are built as .so files,
and LD handles linking them together. This is a pretty standard shared build
usage, and likely very familiar to everyone.
When enabling CPU ISA detection in OVS, we were very careful to not build
the whole OVS code with CPU specific CFLAGS like -mavx512f. To limit scope
of
these CFLAGS, it is common practice to build a static library. The resulting .a
archive file (containing CPU specific ISA) is then static linked into the
vswitchd
binary.
Isn't it better to link libopenvswitchavx512.a to libopenvswitch.{a,so} instead
of linking it to the vswitchd binary? This should allow us to not distribute
it separately inside the package.
There are few issues here:
1. libopenvswitchavx512.a is a confusing name, because it contains only one
object
lib/dpif-netdev-lookup-avx512-gather.c and not the whole library.
2. vswitchd by itself doesn't use dpif-netdev-lookup-* stuff. These things are
only used by libopenvswitch. So, linking of libopenvswitchavx512.a into
vswitchd doesn't make much logical sense.
3. If someone will try to create a different application on top of
libopenvswitch
shared library, they will need to additionally statically link
libopenvswitchavx512.a. Otherwise build will fail, right?
Apologies - a mistake on my side in the email description above.
All 3 of your concerns are resolved by the correction I think?
Clarifying here:
libopenvswitchavx512 is linked into libopenvswitch.
vswitchd always links against libopenvswitch.
Other binaries also link against libopenvswitch.
No specific changes are required to pick up the avx512 for binaries (eg
vswitchd).
This is apparent from the build-system changes - no patches to vswitchd
makefiles.
Hmm. OK. So, we should not ship this static library as it already linked
into libopenvswitch and should not be used by anyone.
Maybe I'm missing something obvious, but I see following while building
with static libs:
- https://travis-ci.org/github/openvswitch/ovs/jobs/707655283#L2179
This line doesn't seem to include libopenvswitchavx512 anyhow.
- And I do see libopenvswitchavx512.a in a linker command while linking ovs-
vswitchd:
https://travis-ci.org/github/openvswitch/ovs/jobs/707655283#L2572
Correct. From the automake.mk file;
# plain vswitch library compiled as normal library, without CPU specific ISA
CFLAGS
lib_LTLIBRARIES += lib/libopenvswitch.la
lib_libopenvswitch_la_SOURCES = <all lib/* source files here>
# Define avx512 library, with CPU ISA specific flags
lib_LTLIBRARIES += lib/libopenvswitchavx512.la
lib_libopenvswitchavx512_la_CFLAGS = <CPU ISA CFLAGS here, -mavx512f etc>
# plain vswitch library has a dependency on vswitchavx512
lib_libopenvswitch_la_LIBADD += lib/libopenvswitchavx512.la
I'm losing track of the actual issue here. What is the concern that we're
discussing?
If packaging ignores the static archive libopenvswitchavx512.a then all is OK?
Correct. That is the initial issue. Not knowing why this suddenly
occurred I added it to the dist to fix the bug. However, I think
this patch from Roi Dayan is better.
https://mail.openvswitch.org/pipermail/ovs-dev/2020-July/372955.html
Thanks,
- Greg
The approach of building application as shared or static, but always
statically
linking
in ISA specialized static libraries into the result is common in other packet
processing
projects. For example, DPDK's ethdev drivers take a similar approach.
As a result, it is expected that static archive files will be linked into the
vswitchd binary, and the
above patch solves exactly that for the .spec file. Regardless of the type of
build (shared/static) of
OVS, the same .a files will require linking, so I see this as a potential fix.
If OVS community feels that all object files must be .so if using --enable-
shared,
then we can revert to the previous method quite easily, just removing the -
static flag
should do from lib/automake.mk. Commenting the below line achieves this:
# lib_libopenvswitchavx512_la_LDFLAGS = -static
With that above change, the shared build of OVS links to a separate .so for
avx512.
$ ldd lib/.libs/libopenvswitch.so
libopenvswitchavx512.so.0 =>
~/path/to/ovs/lib/.libs/libopenvswitchavx512.so.0 (0x00007f2a2c55d000)
Note in this case, the .spec file handles the .so with the %{_libdir}/lib*.so.*
glob,
so no changes would be required due to the wildcarding in place already.
Harry, Ian, could you, please, take a look?
Thanks for flagging, detailed response above. We have two solutions:
1) Keep static linking as today, and add the proposed line in the .spec file as
per patch
2) Remove the -static flag, doing shared builds of ISA optimized code and
linking with LD.
I took approach 1) in the patchset, but switching to 2) is a one-line change as
above.
Developers/testers: please run "make clean" and "boot.sh" before configure,
the build gets
confused without make clean, and will give strange linker errors on the SO
version otherwise.
Best regards, Ilya Maximets.
Regards, -Harry
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