I've sent the following to Andrea Arcangeli.
The problem only occurred when kswapd0 was active, so a previous attempt
at git-bisecting where I didn't force swapping didn't work.
In the following case I was aided by the release of ALSA 1.0.24, which I
compiled against each git-bisect attempt and kept ALSA constant whilst
varying the kernel.
[forwarded email follows]
I'm experiencing MIDI playback slow-downs when I'm observing kswapd0
active (a few percent of cpu in top output) in recent kernels.
I git-bisected the problem down to:
commit 5a03b051ed87e72b959f32a86054e1142ac4cf55
Author: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Date: Thu Jan 13 15:47:11 2011 -0800
thp: use compaction in kswapd for GFP_ATOMIC order > 0
This takes advantage of memory compaction to properly generate pages of
order > 0 if regular page reclaim fails and priority level becomes more
severe and we don't reach the proper watermarks.
Signed-off-by: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
:040000 040000 d67655e822b77c982c0622b9f4fd747af45e4a3e
07b6d3365382d8d5f9afd7e2
56ec5439a0835b72 M include
:040000 040000 307802493526b8b5555fe109a6e0654e24af7a84
48f409b4b07bc2c680f86a23
bdda7f5ced0fe436 M mm
I ran git-bisect over the weekend, building and installing ALSA 1.0.24
with each kernel. After identifying the above commit, I rebuilt the 2.6
head with that commit reverted and verified that the problem was no
longer present.
MIDI playback was via aplaymidi -p 17:0 to a Soundblaster Audigy 2 ZS
(SB0350) wavetable.
The machine has a Pentium II-266 CPU, 440BX chipset on a Biostar M6TBC
motherboard, and RAM is at the maximum supported amount, 384 MiB.
Output from "sh ver_linux":
If some fields are empty or look unusual you may have an old version.
Compare to the current minimal requirements in Documentation/Changes.
Linux victoria 2.6.37+ #14 SMP Sun Feb 20 18:46:21 CST 2011 i686 GNU/Linux
Gnu C 4.4.5
Gnu make 3.81
binutils 2.20.1
util-linux ver_linux: line 23: fdformat: command not found
mount support
module-init-tools found
Linux C Library 2.11.2
Dynamic linker (ldd) 2.11.2
Procps 3.2.8
Kbd 1.15.2
Sh-utils 8.5
Modules Loaded snd_hrtimer tun parport_pc ppdev lp parport
binfmt_misc decnet microcode fuse nls_utf8 nls_cp437 vfat fat
snd_emu10k1_synth snd_emux_synth snd_seq_virmidi snd_seq_midi_emul
snd_emu10k1 snd_ac97_codec ac97_bus snd_pcm_oss snd_mixer_oss snd_pcm
snd_util_mem snd_hwdep snd_seq_dummy snd_seq_oss snd_seq_midi
snd_rawmidi radeon snd_seq_midi_event snd_seq ttm snd_timer
drm_kms_helper snd_seq_device drm snd i2c_algo_bit power_supply
i2c_piix4 shpchp psmouse i2c_core emu10k1_gp soundcore evdev gameport
snd_page_alloc pci_hotplug serio_raw pcspkr ext3 jbd mbcache raid1
md_mod sg sr_mod usb_storage sd_mod cdrom ata_generic crc_t10dif uas
ata_piix libata uhci_hcd ehci_hcd eata usbcore scsi_mod 8139too
firewire_ohci 8139cp firewire_core mii crc_itu_t nls_base
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