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SubjectRe: 2.5.62-mm2 slow file system writes across multiple disks
On Mon, Feb 24, 2003 at 01:53:23PM -0800, Andrew Morton wrote:

> Could be that concurrent umount isn't a good way of getting scalable
> writeout; I can't say that I've ever looked...
>
> Could you try putting a `sync' in there somewhere?
>
> Or even better, throw away dd and use write-and-fsync from ext3 CVS. Give it
> the -f flag to force an fsync against each file as it is closed.
>
> http://www.zip.com.au/~akpm/linux/ext3/

Using fsync didn't seem to make any difference.

I moved to 2.5.62-mm3 [I had to drop back to qlogicisp for my boot disk,
and run the feral drver as a module in order to boot without hanging], and
ran write-and-fsync with -f, with and without -o (O_DIRECT).

What keeps pdflush running when get_request_wait sleeps? I thought there
was (past tense) some creation of multiple pdflushes to handle such cases.

Here are more details:

[patman@elm3b79 iostuff]$ cat /proc/cmdline
BOOT_IMAGE=2562-mm3-1 ro root=801 BOOT_FILE=/boot/vmlinuz-2562-mm3 console=tty0 console=ttyS0,38400 notsc elevator=deadline

Write 10 100 mb files to 10 different disks, write-and-fsync with -f and -o:

[patman@elm3b79 iostuff]$ vmstat 1 10000
procs memory swap io system cpu
r b w swpd free buff cache si so bi bo in cs us sy id
0 0 0 0 8070944 12756 21344 0 0 2 713 162 10 0 1 99
0 0 0 0 8070944 12756 21344 0 0 0 0 1123 6 0 0 100
0 0 0 0 8070944 12756 21344 0 0 0 0 1026 4 0 0 100
0 10 0 0 8069840 12756 21344 0 0 0 39936 1149 194 1 4 95
0 10 0 0 8069816 12772 21344 0 0 0 101500 1502 221 0 4 96
0 10 0 0 8069816 12772 21344 0 0 0 83968 1200 167 0 4 96
0 10 0 0 8069816 12772 21344 0 0 0 80896 1197 164 0 4 96
0 10 0 0 8069816 12772 21344 0 0 0 83968 1192 169 0 4 96
0 10 1 0 8069816 12776 21344 0 0 0 84996 1206 178 0 4 96
0 10 0 0 8069816 12776 21344 0 0 0 82944 1191 167 0 4 96
0 10 0 0 8069816 12776 21344 0 0 0 80896 1195 164 0 4 96
0 10 0 0 8069816 12776 21344 0 0 0 83968 1196 170 0 4 96
0 10 0 0 8069816 12776 21344 0 0 0 82944 1201 165 0 4 96
0 10 1 0 8069808 12776 21344 0 0 0 86144 1195 173 0 4 95
0 10 0 0 8069744 12776 21344 0 0 0 70896 1389 149 0 4 96
0 2 0 0 8070320 12776 21344 0 0 0 52420 1183 218 0 2 97
0 1 0 0 8070464 12776 21344 0 0 0 10244 1051 33 0 0 100
0 0 0 0 8071016 12776 21344 0 0 0 36 1044 42 0 0 100
0 0 1 0 8071016 12776 21344 0 0 0 4 1026 8 0 0 100


Total elapsed time of the 10 writers:

0.03user 1.83system 0:14.13elapsed 13%CPU (0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (1986major+3228minor)pagefaults 0swaps


Write 10 100 mb files to 10 different disks, write-and-fsync with -f (not
O_DIRECT):

[patman@elm3b79 iostuff]$ vmstat 1 10000
procs memory swap io system cpu
r b w swpd free buff cache si so bi bo in cs us sy id
0 0 0 0 8070976 12920 21344 0 0 2 745 162 10 0 1 99
0 0 0 0 8070976 12920 21344 0 0 0 0 1153 4 0 0 100
0 0 0 0 8070912 12928 21344 0 0 0 28 1028 12 0 0 100
10 0 0 0 8054000 12928 37416 0 0 0 0 1063 114 0 5 95
10 0 0 0 7767944 12928 322948 0 0 0 0 1023 41 0 50 50
10 0 0 0 7482504 12928 604124 0 0 0 0 1025 31 0 50 50
6 4 0 0 7222992 12928 858380 0 0 0 342668 1056 80 0 55 45
0 10 1 0 7032160 12944 1045348 0 0 0 271940 1083 134 0 39 61
0 10 1 0 7032048 12944 1045348 0 0 0 22040 1079 42 0 2 97
0 10 1 0 7031832 12944 1045348 0 0 0 22544 1081 42 0 2 98
0 10 1 0 7031800 12944 1045348 0 0 0 8120 1075 32 0 1 99
0 10 1 0 7031800 12944 1045348 0 0 0 0 1073 92 0 1 99
0 10 1 0 7031800 12944 1045348 0 0 0 0 1072 96 0 1 99
0 10 1 0 7031800 12944 1045348 0 0 0 0 1071 88 0 1 99
0 10 1 0 7031816 12944 1045348 0 0 0 3588 1078 98 0 1 99
0 10 1 0 7031856 12944 1045348 0 0 0 18452 1093 96 0 2 98
0 9 1 0 7031960 12944 1045348 0 0 0 11788 1075 58 0 2 98
0 8 1 0 7032048 12944 1045348 0 0 0 36388 1082 55 0 2 97
0 8 1 0 7032000 12944 1045348 0 0 0 25624 1085 40 0 2 98
0 8 1 0 7031832 12944 1045348 0 0 0 25576 1098 42 0 2 98
0 8 1 0 7031760 12944 1045348 0 0 0 22040 1084 58 0 2 98
0 8 1 0 7031720 12944 1045348 0 0 0 23060 1084 60 0 2 98
0 8 1 0 7031664 12944 1045348 0 0 0 10244 1089 60 0 1 98
0 8 1 0 7031672 12944 1045348 0 0 0 18960 1095 70 0 2 98
0 8 1 0 7031656 12944 1045348 0 0 0 40124 1135 108 0 2 97
0 8 1 0 7031672 12944 1045348 0 0 0 37700 1136 92 0 3 97
0 7 1 0 7031672 12944 1045348 0 0 0 22972 1140 113 0 3 97
0 7 1 0 7031688 12944 1045348 0 0 0 17944 1144 163 0 3 97
0 7 1 0 7031696 12944 1045348 0 0 0 23008 1152 183 0 2 97
0 6 1 0 7031792 12944 1045348 0 0 0 18932 1146 177 0 3 97
0 6 1 0 7031816 12944 1045348 0 0 0 1496 1133 176 0 2 98
0 5 0 0 7032040 12944 1045348 0 0 0 0 1127 34 0 2 98
0 4 0 0 7032312 12944 1045348 0 0 0 44 1131 31 0 1 99
procs memory swap io system cpu
r b w swpd free buff cache si so bi bo in cs us sy id
0 3 0 0 7032688 12944 1045348 0 0 0 8 1098 26 0 1 99
0 3 0 0 7033096 12944 1045348 0 0 0 0 1085 18 0 1 99
0 1 0 0 7033808 12944 1045348 0 0 0 0 1066 24 0 1 99

Total elpased time:

0.04user 14.80system 0:33.35elapsed 44%CPU (0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (1986major+3228minor)pagefaults 0swaps

-- Patrick Mansfield
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