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Revision a0783cd0c810504427777e8aae20d5f4f8b652a0 authored by Corinna Vinschen on 19 November 2019, 09:09:39 UTC, committed by David S. Miller on 20 November 2019, 00:41:11 UTC
During performance testing, I found that one of my r8169 NICs suffered a major performance loss, a 8168c model. Running netperf's TCP_STREAM test didn't return the expected throughput of > 900 Mb/s, but rather only about 22 Mb/s. Strange enough, running the TCP_MAERTS and UDP_STREAM tests all returned with throughput > 900 Mb/s, as did TCP_STREAM with the other r8169 NICs I can test (either one of 8169s, 8168e, 8168f). Bisecting turned up commit 93681cd7d94f83903cb3f0f95433d10c28a7e9a5, "r8169: enable HW csum and TSO" as the culprit. I added my 8168c version, RTL_GIGA_MAC_VER_22, to the code special-casing the 8168evl as per the patch below. This fixed the performance problem for me. Fixes: 93681cd7d94f ("r8169: enable HW csum and TSO") Signed-off-by: Corinna Vinschen <vinschen@redhat.com> Reviewed-by: Heiner Kallweit <hkallweit1@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net>
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percpu_test.c
// SPDX-License-Identifier: GPL-2.0-only
#include <linux/module.h>
/* validate @native and @pcp counter values match @expected */
#define CHECK(native, pcp, expected) \
do { \
WARN((native) != (expected), \
"raw %ld (0x%lx) != expected %lld (0x%llx)", \
(native), (native), \
(long long)(expected), (long long)(expected)); \
WARN(__this_cpu_read(pcp) != (expected), \
"pcp %ld (0x%lx) != expected %lld (0x%llx)", \
__this_cpu_read(pcp), __this_cpu_read(pcp), \
(long long)(expected), (long long)(expected)); \
} while (0)
static DEFINE_PER_CPU(long, long_counter);
static DEFINE_PER_CPU(unsigned long, ulong_counter);
static int __init percpu_test_init(void)
{
/*
* volatile prevents compiler from optimizing it uses, otherwise the
* +ul_one/-ul_one below would replace with inc/dec instructions.
*/
volatile unsigned int ui_one = 1;
long l = 0;
unsigned long ul = 0;
pr_info("percpu test start\n");
preempt_disable();
l += -1;
__this_cpu_add(long_counter, -1);
CHECK(l, long_counter, -1);
l += 1;
__this_cpu_add(long_counter, 1);
CHECK(l, long_counter, 0);
ul = 0;
__this_cpu_write(ulong_counter, 0);
ul += 1UL;
__this_cpu_add(ulong_counter, 1UL);
CHECK(ul, ulong_counter, 1);
ul += -1UL;
__this_cpu_add(ulong_counter, -1UL);
CHECK(ul, ulong_counter, 0);
ul += -(unsigned long)1;
__this_cpu_add(ulong_counter, -(unsigned long)1);
CHECK(ul, ulong_counter, -1);
ul = 0;
__this_cpu_write(ulong_counter, 0);
ul -= 1;
__this_cpu_dec(ulong_counter);
CHECK(ul, ulong_counter, -1);
CHECK(ul, ulong_counter, ULONG_MAX);
l += -ui_one;
__this_cpu_add(long_counter, -ui_one);
CHECK(l, long_counter, 0xffffffff);
l += ui_one;
__this_cpu_add(long_counter, ui_one);
CHECK(l, long_counter, (long)0x100000000LL);
l = 0;
__this_cpu_write(long_counter, 0);
l -= ui_one;
__this_cpu_sub(long_counter, ui_one);
CHECK(l, long_counter, -1);
l = 0;
__this_cpu_write(long_counter, 0);
l += ui_one;
__this_cpu_add(long_counter, ui_one);
CHECK(l, long_counter, 1);
l += -ui_one;
__this_cpu_add(long_counter, -ui_one);
CHECK(l, long_counter, (long)0x100000000LL);
l = 0;
__this_cpu_write(long_counter, 0);
l -= ui_one;
this_cpu_sub(long_counter, ui_one);
CHECK(l, long_counter, -1);
CHECK(l, long_counter, ULONG_MAX);
ul = 0;
__this_cpu_write(ulong_counter, 0);
ul += ui_one;
__this_cpu_add(ulong_counter, ui_one);
CHECK(ul, ulong_counter, 1);
ul = 0;
__this_cpu_write(ulong_counter, 0);
ul -= ui_one;
__this_cpu_sub(ulong_counter, ui_one);
CHECK(ul, ulong_counter, -1);
CHECK(ul, ulong_counter, ULONG_MAX);
ul = 3;
__this_cpu_write(ulong_counter, 3);
ul = this_cpu_sub_return(ulong_counter, ui_one);
CHECK(ul, ulong_counter, 2);
ul = __this_cpu_sub_return(ulong_counter, ui_one);
CHECK(ul, ulong_counter, 1);
preempt_enable();
pr_info("percpu test done\n");
return -EAGAIN; /* Fail will directly unload the module */
}
static void __exit percpu_test_exit(void)
{
}
module_init(percpu_test_init)
module_exit(percpu_test_exit)
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Greg Thelen");
MODULE_DESCRIPTION("percpu operations test");
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