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SubjectRe: [PATCH] concurrent block allocation for ext2 against 2.5.64
William Lee Irwin III <wli@holomorphy.com> wrote:
>
> On Fri, Mar 14, 2003 at 10:20:24AM +0300, Alex Tomas wrote:
> > and corrected patch:
>
> This patch is a godsend. Whoever's listening, please apply!
>
> dbench on 32x/48G NUMA-Q, aic7xxx adapter, pbay disk, 32K PAGE_SIZE
> (pgcl was used for benchmark feasibility purposes)
>
> throughput:
> ----------
> before:
> Throughput 61.5376 MB/sec 512 procs
> dbench 512 637.21s user 15739.41s system 565% cpu 48:16.28 total
>
> after:
> Throughput 104.074 MB/sec 512 procs
> (GRR, didn't do time, took ca. 30 minutes)

`dbench 512' will presumably do lots of IO and spend significant
time in I/O wait. You should see the effects of this change more
if you use fewer clients (say, 32) so it doesn't hit disk.

On quad power4, dbench 32:

Unpatched:

Throughput 334.372 MB/sec (NB=417.965 MB/sec 3343.72 MBit/sec)
Throughput 331.379 MB/sec (NB=414.224 MB/sec 3313.79 MBit/sec)
Throughput 364.151 MB/sec (NB=455.189 MB/sec 3641.51 MBit/sec)
Throughput 333.066 MB/sec (NB=416.332 MB/sec 3330.66 MBit/sec)
Throughput 365.335 MB/sec (NB=456.669 MB/sec 3653.35 MBit/sec)
Throughput 335.523 MB/sec (NB=419.404 MB/sec 3355.23 MBit/sec)
Throughput 334.457 MB/sec (NB=418.071 MB/sec 3344.57 MBit/sec)
Throughput 329.527 MB/sec (NB=411.909 MB/sec 3295.27 MBit/sec)
Throughput 332.721 MB/sec (NB=415.901 MB/sec 3327.21 MBit/sec)
Throughput 328.735 MB/sec (NB=410.919 MB/sec 3287.35 MBit/sec)

patched:

Throughput 335.262 MB/sec (NB=419.078 MB/sec 3352.62 MBit/sec)
Throughput 334.531 MB/sec (NB=418.163 MB/sec 3345.31 MBit/sec)
Throughput 337.366 MB/sec (NB=421.707 MB/sec 3373.66 MBit/sec)
Throughput 334.504 MB/sec (NB=418.13 MB/sec 3345.04 MBit/sec)
Throughput 332.482 MB/sec (NB=415.602 MB/sec 3324.82 MBit/sec)
Throughput 334.69 MB/sec (NB=418.363 MB/sec 3346.9 MBit/sec)
Throughput 370.14 MB/sec (NB=462.675 MB/sec 3701.4 MBit/sec)
Throughput 333.255 MB/sec (NB=416.569 MB/sec 3332.55 MBit/sec)
Throughput 336.065 MB/sec (NB=420.081 MB/sec 3360.65 MBit/sec)
Throughput 334.328 MB/sec (NB=417.91 MB/sec 3343.28 MBit/sec)

No difference at all.

On the quad Xeon (after increasing dirty_ratio and dirty_background_ratio so
I/O was negligible) I was able to measure a 1.5% improvement.

I worry about the hardware you're using there.

> profile:
> --------
>
> ...
> after:
> vma samples %-age symbol name
> c0106ff4 52751908 30.8696 default_idle
> c01dc3b0 28988721 16.9637 __copy_to_user_ll
> c01dc418 8240854 4.82242 __copy_from_user_ll
> c011e472 8044716 4.70764 .text.lock.fork
> c0264bd0 5666004 3.31566 sync_buffer
> c013dd28 4454362 2.60662 .text.lock.vmscan
> c0119058 4291999 2.51161 try_to_wake_up
> c0119dac 4055412 2.37316 scheduler_tick
> c011fadc 3554019 2.07976 profile_hook
> c011a1bc 2866025 1.67715 schedule
> c0119860 2637644 1.54351 load_balance
> c0108140 2433644 1.42413 .text.lock.semaphore
> c0264da0 1406704 0.823181 add_event_entry
> c011c9a4 1370708 0.802117 prepare_to_wait
> c0185e20 1236390 0.723516 ext2_new_block
> c011c4ff 1227452 0.718285 .text.lock.sched
> c013ece4 1148317 0.671977 check_highmem_ptes
> c0113590 1145881 0.670551 mark_offset_tsc

Lots of idle time. Try it with a smaller client count, get the I/O out of
the picture.

>
> vmstat (short excerpt, edited for readability):

With what interval?

> after:
> procs -----------memory---------- -----io---- --system-- ----cpu----
> r b free buff cache bi bo in cs us sy id wa
> 60 11 38659840 533920 9226720 100 1672 2760 1853 5 66 11 18
> 31 23 38565472 531264 9320384 240 1020 1195 1679 2 35 37 26
> 23 23 38384928 521952 9503104 772 3372 5624 5093 2 62 9 27
> 24 31 37945664 518080 9916448 1536 5808 10449 13484 1 45 13 41
> 31 86 37755072 516096 10091104 1040 1916 3672 9744 2 51 15 32
> 24 30 37644352 512864 10192960 900 1612 3184 8414 2 49 12 36
>
> There's a lot of odd things going on in both of the vmstat logs.

Where are all those interrupts coming from?


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