[ovs-dev] [PATCH] dpif-netdev: Allocate dp_netdev_pmd_thread struct by xzalloc_cacheline.
Ilya Maximets
i.maximets at samsung.com
Fri Dec 8 13:53:47 UTC 2017
On 08.12.2017 16:45, Stokes, Ian wrote:
>> All instances of struct dp_netdev_pmd_thread are allocated by xzalloc and
>> therefore doesn't guarantee memory allocation aligned on CACHE_LINE_SIZE
>> boundary. Due to this any padding done inside the structure with this
>> assumption might create holes.
>>
>> This commit replaces xzalloc, free with xzalloc_cacheline and
>> free_cacheline. With the changes the memory is 64 byte aligned.
>
> Thanks for this Bhanu,
>
> I think this looks OK and I'm considering pushing to the DPDK_Merge branch but as there has been a fair bit of debate lately regarding memory and cache alignment I want to flag to others who have engaged to date to have their say before I apply it as there has been no input yet for the patch.
>
> @Jan/Ilya, are you ok with this change?
OVS will likely crash on destroying non_pmd thread because it still
allocated by usual xzalloc, but freed with others by free_cacheline().
>
> Thanks
> Ian
>
>>
>> Before:
>> With xzalloc, all the memory is 16 byte aligned.
>>
>> (gdb) p pmd
>> $1 = (struct dp_netdev_pmd_thread *) 0x7eff8a813010
>> (gdb) p &pmd->cacheline0
>> $2 = (OVS_CACHE_LINE_MARKER *) 0x7eff8a813010
>> (gdb) p &pmd->cacheline1
>> $3 = (OVS_CACHE_LINE_MARKER *) 0x7eff8a813050
>> (gdb) p &pmd->flow_cache
>> $4 = (struct emc_cache *) 0x7eff8a813090
>> (gdb) p &pmd->flow_table
>> $5 = (struct cmap *) 0x7eff8acb30d0
>> (gdb) p &pmd->stats
>> $6 = (struct dp_netdev_pmd_stats *) 0x7eff8acb3110
>> (gdb) p &pmd->port_mutex
>> $7 = (struct ovs_mutex *) 0x7eff8acb3150
>> (gdb) p &pmd->poll_list
>> $8 = (struct hmap *) 0x7eff8acb3190
>> (gdb) p &pmd->tnl_port_cache
>> $9 = (struct hmap *) 0x7eff8acb31d0
>> (gdb) p &pmd->stats_zero
>> $10 = (unsigned long long (*)[5]) 0x7eff8acb3210
>>
>> After:
>> With xzalloc_cacheline, all the memory is 64 byte aligned.
>>
>> (gdb) p pmd
>> $1 = (struct dp_netdev_pmd_thread *) 0x7f39e2365040
>> (gdb) p &pmd->cacheline0
>> $2 = (OVS_CACHE_LINE_MARKER *) 0x7f39e2365040
>> (gdb) p &pmd->cacheline1
>> $3 = (OVS_CACHE_LINE_MARKER *) 0x7f39e2365080
>> (gdb) p &pmd->flow_cache
>> $4 = (struct emc_cache *) 0x7f39e23650c0
>> (gdb) p &pmd->flow_table
>> $5 = (struct cmap *) 0x7f39e2805100
>> (gdb) p &pmd->stats
>> $6 = (struct dp_netdev_pmd_stats *) 0x7f39e2805140
>> (gdb) p &pmd->port_mutex
>> $7 = (struct ovs_mutex *) 0x7f39e2805180
>> (gdb) p &pmd->poll_list
>> $8 = (struct hmap *) 0x7f39e28051c0
>> (gdb) p &pmd->tnl_port_cache
>> $9 = (struct hmap *) 0x7f39e2805200
>> (gdb) p &pmd->stats_zero
>> $10 = (unsigned long long (*)[5]) 0x7f39e2805240
>>
>> Reported-by: Ilya Maximets <i.maximets at samsung.com>
>> Signed-off-by: Bhanuprakash Bodireddy <bhanuprakash.bodireddy at intel.com>
>> ---
>> lib/dpif-netdev.c | 4 ++--
>> 1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/lib/dpif-netdev.c b/lib/dpif-netdev.c index db78318..3e281ae
>> 100644
>> --- a/lib/dpif-netdev.c
>> +++ b/lib/dpif-netdev.c
>> @@ -3646,7 +3646,7 @@ reconfigure_pmd_threads(struct dp_netdev *dp)
>> FOR_EACH_CORE_ON_DUMP(core, pmd_cores) {
>> pmd = dp_netdev_get_pmd(dp, core->core_id);
>> if (!pmd) {
>> - pmd = xzalloc(sizeof *pmd);
>> + pmd = xzalloc_cacheline(sizeof *pmd);
>> dp_netdev_configure_pmd(pmd, dp, core->core_id, core-
>>> numa_id);
>> pmd->thread = ovs_thread_create("pmd", pmd_thread_main, pmd);
>> VLOG_INFO("PMD thread on numa_id: %d, core id: %2d created.",
>> @@ -4574,7 +4574,7 @@ dp_netdev_destroy_pmd(struct dp_netdev_pmd_thread
>> *pmd)
>> xpthread_cond_destroy(&pmd->cond);
>> ovs_mutex_destroy(&pmd->cond_mutex);
>> ovs_mutex_destroy(&pmd->port_mutex);
>> - free(pmd);
>> + free_cacheline(pmd);
>> }
>>
>> /* Stops the pmd thread, removes it from the 'dp->poll_threads',
>> --
>> 2.4.11
>>
>> _______________________________________________
>> dev mailing list
>> dev at openvswitch.org
>> https://mail.openvswitch.org/mailman/listinfo/ovs-dev
>
>
>
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