Re: 2.6.0-test9 - poor swap performance on low end machines

From: Pasi Savolainen
Date: Sat Nov 01 2003 - 13:36:42 EST

* Ed Tomlinson <edt@xxxxxx>:
> On October 31, 2003 06:26 am, Roger Luethi wrote:
>> On Thu, 30 Oct 2003 22:57:23 -0500, Rik van Riel wrote:
>>
>> > On Wed, 29 Oct 2003, Chris Vine wrote:
>> >
>> >
>> > > However, on a low end machine (200MHz Pentium MMX uniprocessor with
>> > > only 32MB
of RAM and 70MB of swap) I get poor performance once
>> > > extensive use is made of the swap space.
>> >
>> >
>> > Could you try the patch Con Kolivas posted on the 25th ?
>> >
>> > Subject: [PATCH] Autoregulate vm swappiness cleanup
>>
>>
>> I suppose it will show some improvement but fail to get performance
>> anywhere near 2.4 -- at least that's what my own tests found. I've been
>> working on a break-down of where we're losing it.
>> Bottom line: It's not simply a price we pay for feature X or Y. It's
>> all over the map, and thus no single patch can possibly fix it.
>
> With 2.6 its possible to tell the kernel how much to swap. Con's patch
> tries to keep applications in memory. You can also play with
> /proc/sys/vm/swappiness which is what Con's patch tries to replace.

FWIW, I've been getting horrible performance when FREEING swap space. UI
would just hang for several seconds. It've been that way all the -test
timeframe.
test9 has been much better, but seemingly only because it doesn't seem
to like swap as good as before, it doesn't use it unless in dire need.

It's not exactly low-end machine either: 2x1800, 512M + 1G swap.
DMA is on for IDE.

below is 'vmstat 1', I loaded some 30MB images into GIMP and made tight
operations (undo level at 100). Loaded some more heavy apps, then moved
to GIMP's workspace and closed it. There was 'no-response' -time at
marked places:

procs -----------memory---------- ---swap-- -----io---- --system-- ----cpu----
r b swpd free buff cache si so bi bo in cs us sy id wa
...
1 1 318784 6788 9500 134092 964 0 1652 220 1262 1185 9 2 44 46
0 1 318784 5188 9512 134164 1548 0 1620 4 1162 861 8 1 32 59
0 1 318784 3140 9268 132052 8000 0 8000 0 1299 1130 4 2 48 46
0 2 331280 2812 8860 127072 7360 13336 7360 13336 1502 1700 1 4 44 51
0 1 331280 3800 8644 125816 4648 0 4648 4 1368 1330 1 3 29 67
0 2 333596 3104 8632 125312 3136 2340 3136 2372 1466 1809 2 4 44 51
1 2 336548 3620 8588 124924 5736 2972 5736 2972 1658 2163 3 5 23 69
0 2 336468 3752 8668 124836 736 92 816 112 1454 1697 3 4 23 71
0 1 336468 5232 8760 123288 5468 0 5536 136 1694 2265 3 4 28 65
- click GIMP 'Quit' -
1 0 334848 4680 8808 124088 2200 0 3000 56 1339 1404 3 2 34 61
0 1 291692 150596 8812 124496 876 0 1248 0 1232 1116 13 3 48 36
- GUI freeze -
0 1 291692 148432 8812 124164 2576 0 2576 0 1369 561 1 1 50 49
0 1 291692 146128 8812 124132 2344 0 2344 0 1284 488 1 1 50 49
0 2 291692 143828 8812 124048 2396 0 2396 28 1254 373 0 2 49 49
0 2 291692 141588 8828 124092 2320 0 2320 52 1270 583 0 1 6 92
0 2 291692 139228 8848 124044 2272 0 2272 32 1257 524 0 1 13 86
procs -----------memory---------- ---swap-- -----io---- --system-- ----cpu----
r b swpd free buff cache si so bi bo in cs us sy id wa
1 1 291692 136988 8848 124064 2224 0 2224 0 1213 401 1 1 50 49
0 1 291692 134688 8848 124048 2328 0 2328 0 1349 362 1 1 49 49
0 1 291692 132128 8848 124040 2524 0 2524 0 1408 371 0 2 49 49
0 1 291692 129824 8848 124028 2324 0 2324 0 1210 361 0 1 49 50
0 1 291692 127520 8852 124044 2292 0 2292 164 1266 474 0 1 29 69
0 2 291692 125348 8868 124060 2144 0 2144 28 1225 473 0 2 8 90
0 2 291692 122788 8888 124100 2524 0 2524 32 1283 557 1 1 24 75
0 1 291692 120612 8888 124092 2184 0 2184 0 1181 367 0 1 43 56
0 1 291692 118052 8888 124092 2516 0 2516 0 1176 346 1 1 50 49
0 1 291692 115684 8888 124068 2404 0 2404 0 1178 337 1 1 50 49
0 1 291692 113124 8888 124112 2540 0 2540 0 1183 349 1 1 50 49
0 1 291692 111080 8888 123688 2464 0 2464 0 1186 336 1 1 49 50
0 0 291692 109920 8924 123712 1164 0 1164 60 1165 869 3 1 57 39
- GUI available -
0 0 291692 109924 8924 123712 0 0 0 0 1079 632 0 0 100 0
0 0 291692 109924 8924 123712 0 0 0 0 1079 687 0 0 100 0
0 0 291692 109924 8924 123712 0 0 0 0 1074 645 0 0 100 0
0 0 291692 109928 8924 123712 0 0 0 0 1122 797 1 0 100 0


--
Psi -- <http://www.iki.fi/pasi.savolainen>
Vivake -- Virtuaalinen valokuvauskerho <http://members.lycos.co.uk/vivake/>

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