RE: [PATCH 0/3] blk-mq: improve IO perf in case of none io sched

[Kashyap Desai <kashyap.desai@broadcom.com>]

Ming -

Performance drop is resolved on my setup, but may be some stability of the
kernel is caused due to this patch set. I have not tried without patch
set, but in case you can figure out if below crash is due to this patch
set, I can try potential fix as well.  I am seeing kernel panic if I use
below three settings in my fio script.

iodepth_batch=8
iodepth_batch_complete_min=4
iodepth_batch_complete_max=16


Here is panic detail -

[65237.831029] ------------[ cut here ]------------
[65237.831031] list_add corruption. prev->next should be next
(ffffbb1d0a41fdf8), but was ffff94d0f0c57240. (prev=ffff94d0f0c57240).
[65237.831046] WARNING: CPU: 18 PID: 13897 at lib/list_debug.c:28
__list_add_valid+0x6a/0x70
[65237.831046] Modules linked in: mpt3sas raid_class ses enclosure
scsi_transport_sas megaraid_sas(OE) xt_CHECKSUM ipt_MASQUERADE tun
ip6t_rpfilter ipt_REJECT nf_reject_ipv4 ip6t_REJECT nf_reject_ipv6
xt_conntrack ip_set nfnetlink ebtable_nat ebtable_broute bridge stp llc
ip6table_nat nf_conntrack_ipv6 nf_defrag_ipv6 nf_nat_ipv6 ip6table_mangle
ip6table_security ip6table_raw iptable_nat nf_conntrack_ipv4
nf_defrag_ipv4 nf_nat_ipv4 nf_nat nf_conntrack iptable_mangle
iptable_security iptable_raw ebtable_filter ebtables ip6table_filter
ip6_tables iptable_filter intel_rapl skx_edac nfit libnvdimm
x86_pkg_temp_thermal intel_powerclamp coretemp kvm_intel kvm irqbypass
crct10dif_pclmul crc32_pclmul ghash_clmulni_intel pcbc aesni_intel
snd_hda_codec_realtek snd_hda_codec_generic snd_hda_intel crypto_simd
cryptd
[65237.831079]  snd_hda_codec snd_hda_core glue_helper snd_hwdep iTCO_wdt
snd_seq iTCO_vendor_support snd_seq_device pcspkr snd_pcm sg i2c_i801
joydev wmi mei_me ipmi_si mei snd_timer acpi_power_meter ioatdma snd
acpi_pad ipmi_devintf ipmi_msghandler soundcore lpc_ich nfsd auth_rpcgss
nfs_acl lockd grace sunrpc ip_tables xfs libcrc32c sd_mod ast i2c_algo_bit
drm_kms_helper syscopyarea sysfillrect sysimgblt fb_sys_fops ttm drm ixgbe
ahci libahci crc32c_intel libata mdio i2c_core dca dm_mirror
dm_region_hash dm_log dm_mod
[65237.831109] CPU: 18 PID: 13897 Comm: fio Kdump: loaded Tainted: G
OE     4.18.0-rc1+ #1
[65237.831110] Hardware name: Supermicro Super Server/X11DPG-QT, BIOS 1.0
06/22/2017
[65237.831112] RIP: 0010:__list_add_valid+0x6a/0x70
[65237.831112] Code: 31 c0 48 c7 c7 90 08 ab a0 e8 22 b4 cd ff 0f 0b 31 c0
c3 48 89 d1 48 c7 c7 40 08 ab a0 48 89 f2 48 89 c6 31 c0 e8 06 b4 cd ff
<0f> 0b 31 c0 c3 90 48 8b 07 48 b9 00 01 00 00 00 00 ad de 48 8b 57
[65237.831130] RSP: 0018:ffffbb1d0a41fdd8 EFLAGS: 00010286
[65237.831131] RAX: 0000000000000000 RBX: ffff94d0ebf90000 RCX:
0000000000000006
[65237.831132] RDX: 0000000000000000 RSI: 0000000000000086 RDI:
ffff94d91ec16970
[65237.831132] RBP: ffffdb1cff59e980 R08: 0000000000000000 R09:
0000000000000663
[65237.831133] R10: 0000000000000004 R11: 0000000000000000 R12:
0000000000000001
[65237.831134] R13: 0000000000000000 R14: ffff94d0f0c57240 R15:
ffff94d0f0f04c40
[65237.831135] FS:  00007fad10d02740(0000) GS:ffff94d91ec00000(0000)
knlGS:0000000000000000
[65237.831135] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[65237.831136] CR2: 00007fad10c2a004 CR3: 000000085600e006 CR4:
00000000007606e0
[65237.831137] DR0: 0000000000000000 DR1: 0000000000000000 DR2:
0000000000000000
[65237.831138] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7:
0000000000000400
[65237.831138] PKRU: 55555554
[65237.831138] Call Trace:
[65237.831145]  blk_mq_flush_plug_list+0x12d/0x260
[65237.831150]  blk_flush_plug_list+0xe7/0x240
[65237.831152]  blk_finish_plug+0x27/0x40
[65237.831156]  __x64_sys_io_submit+0xc9/0x180
[65237.831162]  do_syscall_64+0x5b/0x180
[65237.831166]  entry_SYSCALL_64_after_hwframe+0x44/0xa9


Kashyap

> -----Original Message-----
> From: Ming Lei [mailto:ming.lei@redhat.com]
> Sent: Thursday, June 28, 2018 8:49 AM
> To: Jens Axboe
> Cc: linux-block@vger.kernel.org; Ming Lei; Kashyap Desai; Laurence
Oberman;
> Omar Sandoval; Christoph Hellwig; Bart Van Assche; Hannes Reinecke
> Subject: [PATCH 0/3] blk-mq: improve IO perf in case of none io sched
>
> Hi,
>
> The 1st 2 patch improves ctx->lock uses, and it is observed that IOPS
> may be improved by ~5% in rand IO test on MegaRaid SAS run by Kashyap.
>
> The 3rd patch fixes rand IO performance regression on MegaRaid SAS
> test, still reported by Kashyap.
>
> Ming Lei (3):
>   blk-mq: use list_splice_tail() to insert requests
>   blk-mq: only attempt to merge bio if there is rq in sw queue
>   blk-mq: dequeue request one by one from sw queue iff hctx is busy
>
>  block/blk-mq-sched.c   | 14 ++++----------
>  block/blk-mq.c         | 38 ++++++++++++++++++++++++++++++--------
>  include/linux/blk-mq.h |  1 +
>  3 files changed, 35 insertions(+), 18 deletions(-)
>
> Cc: Kashyap Desai <kashyap.desai@broadcom.com>
> Cc: Laurence Oberman <loberman@redhat.com>
> Cc: Omar Sandoval <osandov@fb.com>
> Cc: Christoph Hellwig <hch@lst.de>
> Cc: Bart Van Assche <bart.vanassche@wdc.com>
> Cc: Hannes Reinecke <hare@suse.de>
>
> --
> 2.9.5