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[Bug kprobes/10839] kretprobes use excessive memory on x86_64 rawhide
- From: "jistone at redhat dot com" <sourceware-bugzilla at sourceware dot org>
- To: systemtap at sources dot redhat dot com
- Date: 26 Oct 2009 23:07:14 -0000
- Subject: [Bug kprobes/10839] kretprobes use excessive memory on x86_64 rawhide
- References: <20091024022959.10839.jistone@redhat.com>
- Reply-to: sourceware-bugzilla at sourceware dot org
------- Additional Comments From jistone at redhat dot com 2009-10-26 23:07 -------
(In reply to comment #1)
> Might this be accounted for by a change to NR_CPUs leading
> to an excessive default kretprobe .maxactive? Try setting
> a low -DKRETACTIVE=nnn parameter.
Ah -- indeed, on x86_64 NR_CPUS = 512, where on F11 it was only 64. We default
to 6*NR_CPUS, but that still doesn't account for it:
(2802 probes)*(6*512 maxactive)*(40b kretprobe_instance) = ~330MB
A different measurement:
# stap -e 'probe kernel.function("*@fs/*").return { next }' -DKRETACTIVE=100 -c free
total used free shared buffers cached
Mem: 458900 398628 60272 0 7488 148036
-/+ buffers/cache: 243104 215796
Swap: 522104 1260 520844
# stap -e 'probe kernel.function("*@fs/*").return { next }' -DKRETACTIVE=200 -c free
total used free shared buffers cached
Mem: 458900 435944 22956 0 7488 148012
-/+ buffers/cache: 280444 178456
Swap: 522104 1260 520844
That's 37MB for a change of 100 maxactive, which comes to about 136 bytes each.
--
http://sourceware.org/bugzilla/show_bug.cgi?id=10839
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