Hi Hannes,
Sorry for the delay in replying, I observed a few issues with this
patchset:
1. "blk_mq_unique_tag_to_hwq(tag)" does not return MSI-x vector to
which IO submitter CPU is affined with. Due to this IO submission and
completion CPUs are different which causes performance drop for low
latency workloads.
Hi Sumit,
So the new code has:
megasas_build_ldio_fusion()
{
cmd->request_desc->SCSIIO.MSIxIndex =
blk_mq_unique_tag_to_hwq(tag);
}
So the value here is hw queue index from blk-mq point of view, and not
megaraid_sas msix index, as you alluded to.
So we get 80 msix, 8 are reserved for low_latency_index_start (that's
how it seems to me), and we report other 72 as #hw queues = 72 to SCSI
midlayer.
So I think that this should be:
cmd->request_desc->SCSIIO.MSIxIndex =
blk_mq_unique_tag_to_hwq(tag) + low_latency_index_start;
Indeed, that sounds reasonable.
(The whole queue mapping stuff isn't exactly well documented :-( )
Yeah, there's certainly lots of knobs and levers in this driver.
I'll be updating the patch.
About this one:
> 2. Seeing below stack traces/messages in dmesg during driver unload –
>
> [2565601.054366] Call Trace:
> [2565601.054368] blk_mq_free_map_and_requests+0x28/0x50
> [2565601.054369] blk_mq_free_tag_set+0x1d/0x90
> [2565601.054370] scsi_host_dev_release+0x8a/0xf0
> [2565601.054370] device_release+0x27/0x80
> [2565601.054371] kobject_cleanup+0x61/0x190
> [2565601.054373] megasas_detach_one+0x4c1/0x650 [megaraid_sas]
> [2565601.054374] pci_device_remove+0x3b/0xc0
> [2565601.054375] device_release_driver_internal+0xec/0x1b0
> [2565601.054376] driver_detach+0x46/0x90
> [2565601.054377] bus_remove_driver+0x58/0xd0
> [2565601.054378] pci_unregister_driver+0x26/0xa0
> [2565601.054379] megasas_exit+0x91/0x882 [megaraid_sas]
> [2565601.054381] __x64_sys_delete_module+0x16c/0x250
> [2565601.054382] do_syscall_64+0x5b/0x1b0
> [2565601.054383] entry_SYSCALL_64_after_hwframe+0x44/0xa9
> [2565601.054383] RIP: 0033:0x7f7212a82837
> [2565601.054384] RSP: 002b:00007ffdfa2dcea8 EFLAGS: 00000202 ORIG_RAX:
> 00000000000000b0
> [2565601.054385] RAX: ffffffffffffffda RBX: 0000000000b6e2e0 RCX:
> 00007f7212a82837
> [2565601.054385] RDX: 00007f7212af3ac0 RSI: 0000000000000800 RDI:
> 0000000000b6e348
> [2565601.054386] RBP: 0000000000000000 R08: 00007f7212d47060 R09:
> 00007f7212af3ac0
> [2565601.054386] R10: 00007ffdfa2dcbc0 R11: 0000000000000202 R12:
> 00007ffdfa2dd71c
> [2565601.054387] R13: 0000000000000000 R14: 0000000000b6e2e0 R15:
> 0000000000b6e010
> [2565601.054387] ---[ end trace 38899303bd85e838 ]---
I see it also for hisi_sas_v3_hw.
And so I don't understand the code change here, specifically where the
WARN is generated:
void blk_mq_free_rqs(struct blk_mq_tag_set *set, struct blk_mq_tags *tags,
unsigned int hctx_idx)
{
struct page *page;
int i;
if (tags->rqs) {
for (i = 0; i < tags->nr_tags; i++)
if (WARN_ON(tags->rqs[i]))
tags->rqs[i] = NULL; <--- here
}
I thought that tags->rqs[i] was just a holder for a pointer to a static
tag, like assigned here:
static struct request *blk_mq_rq_ctx_init(struct blk_mq_alloc_data *data,
unsigned int tag, unsigned int op, u64 alloc_time_ns)
{
struct blk_mq_tags *tags = blk_mq_tags_from_data(data);
struct request *rq = tags->static_rqs[tag];
...
rq->tag = tag;
rq->internal_tag = -1;
data->hctx->tags->rqs[rq->tag] = rq;
...
}
So I don't know why we need to WARN if unset, and then also clear it.
The memory is freed pretty soon after this anyway.
Thanks,
John
lspcu:
# lscpu
Architecture: x86_64
CPU op-mode(s): 32-bit, 64-bit
Byte Order: Little Endian
CPU(s): 72
On-line CPU(s) list: 0-71
Thread(s) per core: 2
Core(s) per socket: 18
Socket(s): 2
NUMA node(s): 2
Vendor ID: GenuineIntel
CPU family: 6
Model: 85
Model name: Intel(R) Xeon(R) Gold 6150 CPU @ 2.70GHz
Stepping: 4
CPU MHz: 3204.246
CPU max MHz: 3700.0000
CPU min MHz: 1200.0000
BogoMIPS: 5400.00
Virtualization: VT-x
L1d cache: 32K
L1i cache: 32K
L2 cache: 1024K
L3 cache: 25344K
NUMA node0 CPU(s): 0-17,36-53
NUMA node1 CPU(s): 18-35,54-71
Flags: fpu vme de pse tsc msr pae mce cx8 apic sep
mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht
tm pbe s
yscall nx pdpe1gb rdtscp lm constant_tsc art arch_perfmon pebs bts
rep_good nopl xtopology nonstop_tsc cpuid aperfmperf pni pclmulqdq
dtes64 monitor
ds_cpl vmx smx est tm2 ssse3 sdbg fma cx16 xtpr pdcm pcid dca sse4_1
sse4_2 x2apic movbe popcnt tsc_deadline_timer xsave avx f16c rdrand
lahf_lm abm
3dnowprefetch cpuid_fault epb cat_l3 cdp_l3 invpcid_single intel_ppin
mba tpr_shadow vnmi flexpriority ept vpid ept_ad fsgsbase tsc_adjust
bmi1 hle
avx2 smep bmi2 erms invpcid rtm cqm mpx rdt_a avx512f avx512dq rdseed
adx smap clflushopt clwb intel_pt avx512cd avx512bw avx512vl xsaveopt
xsavec
xgetbv1 xsaves cqm_llc cqm_occup_llc cqm_mbm_total cqm_mbm_lo
[snip]
4. This patch removes below code from driver so what this piece of
code does is broken-
- if (instance->adapter_type >=
INVADER_SERIES &&
- !instance->msix_combined) {
- instance->msix_load_balance =
true;
- instance->smp_affinity_enable
= false;
- }
Does this code need to be re-added? Would this have affected your test?
Primarily this patch was required to enable interrupt affinity on my
machine (Lenovo RAID 930-8i).
Can you give me some information why the code is present in the first
place? Some hardware limitation, maybe?
Cheers,
Hannes
