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SubjectRe: [patch] "HT scheduler", sched-2.5.63-B3
At 12:42 PM 3/6/2003 -0800, Andrew Morton wrote:
>Ingo's combo patch is better still - that is sched-2.5.64-a5 and your patch
>combined (yes?). The slight mouse jerkiness is gone and even when doing
>really silly things I cannot make it misbehave at all. I'd handwavingly
>describe both your patch and sched-2.5.64-a5 as 80% solutions, and the combo
>95%.

Weeeeell, FWIW my box (p3-500/128mb/rage128) disagrees.

I can still barely control the box when a make -j5 bzImage is running under
X/KDE in one terminal and a vmstat (SCHED_RR) in another. I'm not swapping,
though a bit of idle junk does page out. IOW, I think I'm seeing serious
cpu starvation.

For reference, I used to be able to easily control the same box under X
while swapping moderately at make -j15 (during page aging vm days), and
with a heavily twiddled VM at even -j30 (_way_ overloaded with X oinkers
running). At -j5, gui/icky was quite usable.

With the make -j30 bzImage, heavy load which does _hit_ VM saturation but
not constantly, I see what I can only describe as starvation. vmstat
output for this load is definitely abby-normal, and there's no way
/proc/vmstat should look like the attached. It takes forever to build
enough vm pressure that swap is touched (bad bad bad), and the volume
reached is way low. My hungry little cc1's are not sharing resources the
way they should be (methinks).

With earlier versions of Ingo's patch, I was only able to get memory
pressure up to where it should be by drastically reducing timeslice (at the
expense of turning throughput to crud). Take this with a giant economy
sized grain of salt, but what I _think_ (no, I haven't instrumented it) is
happening is that chunks of the total job are being rescheduled in front of
the rest of the job such that they alloc/use/exit before the other guys can
alloc. (geez that's a nebulous WAG;)

-Mike (please torch me if I'm being stupid;) box = p3/500/128MB
fresh boot
time make -j30 bzImage
cat /proc/vmstat

2.5.64-B3 2.5.64-virgin
------------------------------------------
nr_dirty 64 2448
nr_writeback 0 0
nr_pagecache 7432 7562
nr_page_table_pages 85 85
nr_reverse_maps 3348 3177
nr_mapped 634 579
nr_slab 1239 1235
pgpgin 288560 692725
pgpgout 228803 587572
pswpin 30734 116097
pswpout 47347 138888
pgalloc 918016 1046369
pgfree 940744 1068983
pgactivate 28577 45566
pgdeactivate 55265 172833
pgfault 1579517 1682466
pgmajfault 8463 28137
pgscan 556041 1678315
pgrefill 211542 643564
pgsteal 77311 194216
pginodesteal 0 0
kswapd_steal 73454 173378
kswapd_inodesteal 11069 11317
pageoutrun 222 509
allocstall 85 480
pgrotated 49798 140956
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