| Message ID | f011968fee563eeaaa82bf94e760e9f612eee356.1706889875.git.pabeni@redhat.com (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | a19747c3b9bf6476cc36d0a3a5ef0ff92999169e |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | [net] selftests: net: let big_tcp test cope with slow env | expand |
On Fri, Feb 2, 2024 at 5:07 PM Paolo Abeni <pabeni@redhat.com> wrote: > > In very slow environments, most big TCP cases including > segmentation and reassembly of big TCP packets have a good > chance to fail: by default the TCP client uses write size > well below 64K. If the host is low enough autocorking is > unable to build real big TCP packets. > > Address the issue using much larger write operations. > > Note that is hard to observe the issue without an extremely > slow and/or overloaded environment; reduce the TCP transfer > time to allow for much easier/faster reproducibility. > > Fixes: 6bb382bcf742 ("selftests: add a selftest for big tcp") > Signed-off-by: Paolo Abeni <pabeni@redhat.com> > --- > tools/testing/selftests/net/big_tcp.sh | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/tools/testing/selftests/net/big_tcp.sh b/tools/testing/selftests/net/big_tcp.sh > index cde9a91c4797..2db9d15cd45f 100755 > --- a/tools/testing/selftests/net/big_tcp.sh > +++ b/tools/testing/selftests/net/big_tcp.sh > @@ -122,7 +122,9 @@ do_netperf() { > local netns=$1 > > [ "$NF" = "6" ] && serip=$SERVER_IP6 > - ip net exec $netns netperf -$NF -t TCP_STREAM -H $serip 2>&1 >/dev/null > + > + # use large write to be sure to generate big tcp packets > + ip net exec $netns netperf -$NF -t TCP_STREAM -l 1 -H $serip -- -m 262144 2>&1 >/dev/null > } Interesting. I think we set tcp_wmem[1] to 262144 in our hosts. I think netperf default depends on tcp_wmem[1] Reviewed-by: Eric Dumazet <edumazet@google.com>
On Fri, Feb 2, 2024 at 11:07 AM Paolo Abeni <pabeni@redhat.com> wrote: > > In very slow environments, most big TCP cases including > segmentation and reassembly of big TCP packets have a good > chance to fail: by default the TCP client uses write size > well below 64K. If the host is low enough autocorking is > unable to build real big TCP packets. > > Address the issue using much larger write operations. > > Note that is hard to observe the issue without an extremely > slow and/or overloaded environment; reduce the TCP transfer > time to allow for much easier/faster reproducibility. > > Fixes: 6bb382bcf742 ("selftests: add a selftest for big tcp") > Signed-off-by: Paolo Abeni <pabeni@redhat.com> Acked-by: Xin Long <lucien.xin@gmail.com>
On Fri, 2024-02-02 at 17:13 +0100, Eric Dumazet wrote: > On Fri, Feb 2, 2024 at 5:07 PM Paolo Abeni <pabeni@redhat.com> wrote: > > > > In very slow environments, most big TCP cases including > > segmentation and reassembly of big TCP packets have a good > > chance to fail: by default the TCP client uses write size > > well below 64K. If the host is low enough autocorking is > > unable to build real big TCP packets. > > > > Address the issue using much larger write operations. > > > > Note that is hard to observe the issue without an extremely > > slow and/or overloaded environment; reduce the TCP transfer > > time to allow for much easier/faster reproducibility. > > > > Fixes: 6bb382bcf742 ("selftests: add a selftest for big tcp") > > Signed-off-by: Paolo Abeni <pabeni@redhat.com> > > --- > > tools/testing/selftests/net/big_tcp.sh | 4 +++- > > 1 file changed, 3 insertions(+), 1 deletion(-) > > > > diff --git a/tools/testing/selftests/net/big_tcp.sh b/tools/testing/selftests/net/big_tcp.sh > > index cde9a91c4797..2db9d15cd45f 100755 > > --- a/tools/testing/selftests/net/big_tcp.sh > > +++ b/tools/testing/selftests/net/big_tcp.sh > > @@ -122,7 +122,9 @@ do_netperf() { > > local netns=$1 > > > > [ "$NF" = "6" ] && serip=$SERVER_IP6 > > - ip net exec $netns netperf -$NF -t TCP_STREAM -H $serip 2>&1 >/dev/null > > + > > + # use large write to be sure to generate big tcp packets > > + ip net exec $netns netperf -$NF -t TCP_STREAM -l 1 -H $serip -- -m 262144 2>&1 >/dev/null > > } > > Interesting. > > I think we set tcp_wmem[1] to 262144 in our hosts. I think netperf > default depends on tcp_wmem[1] I haven't dug into the netperf source, but the above would be consistent with what I observe: in my VM I see 16Kb writes and tcp_wmem[1] is 16K. > Reviewed-by: Eric Dumazet <edumazet@google.com> Thanks! Paolo
Hello: This patch was applied to netdev/net.git (main) by David S. Miller <davem@davemloft.net>: On Fri, 2 Feb 2024 17:06:59 +0100 you wrote: > In very slow environments, most big TCP cases including > segmentation and reassembly of big TCP packets have a good > chance to fail: by default the TCP client uses write size > well below 64K. If the host is low enough autocorking is > unable to build real big TCP packets. > > Address the issue using much larger write operations. > > [...] Here is the summary with links: - [net] selftests: net: let big_tcp test cope with slow env https://git.kernel.org/netdev/net/c/a19747c3b9bf You are awesome, thank you!
diff --git a/tools/testing/selftests/net/big_tcp.sh b/tools/testing/selftests/net/big_tcp.sh index cde9a91c4797..2db9d15cd45f 100755 --- a/tools/testing/selftests/net/big_tcp.sh +++ b/tools/testing/selftests/net/big_tcp.sh @@ -122,7 +122,9 @@ do_netperf() { local netns=$1 [ "$NF" = "6" ] && serip=$SERVER_IP6 - ip net exec $netns netperf -$NF -t TCP_STREAM -H $serip 2>&1 >/dev/null + + # use large write to be sure to generate big tcp packets + ip net exec $netns netperf -$NF -t TCP_STREAM -l 1 -H $serip -- -m 262144 2>&1 >/dev/null } do_test() {
In very slow environments, most big TCP cases including segmentation and reassembly of big TCP packets have a good chance to fail: by default the TCP client uses write size well below 64K. If the host is low enough autocorking is unable to build real big TCP packets. Address the issue using much larger write operations. Note that is hard to observe the issue without an extremely slow and/or overloaded environment; reduce the TCP transfer time to allow for much easier/faster reproducibility. Fixes: 6bb382bcf742 ("selftests: add a selftest for big tcp") Signed-off-by: Paolo Abeni <pabeni@redhat.com> --- tools/testing/selftests/net/big_tcp.sh | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)