Subrata Modak wrote:
Nadia Derbey wrote:
Andrew Morton wrote:
On Mon, 11 Feb 2008 15:16:47 +0100 Nadia.Derbey@xxxxxxxx wrote:
[PATCH 01/08]
This patch computes msg_ctlmni to make it scale with the amount of
lowmem.
msg_ctlmni is now set to make the message queues occupy 1/32 of the
available
lowmem.
Some cleaning has also been done for the MSGPOOL constant: the msgctl
man page
says it's not used, but it also defines it as a size in bytes (the code
expresses it in Kbytes).
Something's wrong here. Running LTP's msgctl08 (specifically:
ltp-full-20070228) cripples the machine. It's a 4-way 4GB x86_64.
http://userweb.kernel.org/~akpm/config-x.txt
http://userweb.kernel.org/~akpm/dmesg-x.txt
Normally msgctl08 will complete in a second or two. With this patch I
don't know how long it will take to complete, and the machine is horridly
bogged down. It does recover if you manage to kill msgctl08. Feels like
a terrible memory shortage, but there's plenty of memory free and it
isn't
swapping.
Before the patchset, msgctl08 used to be run with the old msgmni value:
16. Now it is run with a much higher msgmni value (1746 in my case),
since it scales to the memory size.
When I call "msgctl08 100000 16" it completes fast.
Doing the follwing on the ref kernel:
echo 1746 > /proc/sys/kernel/msgmni
msgctl08 100000 1746
makes th test block too :-(
Will check to see where the problem comes from.
Well, actually, the test does not block, it only takes much much more
time to be executed:
doing this:
date; ./msgctl08 100000 XXX; date
gives us the following results:
XXX 16 32 64 128 256 512 1024 1746
time(secs) 2 4 8 16 32 64 132 241
XXX is the # of msg queues to be created = # of processes to be forked
as readers = # of processes to be created as writers
time is approximative since it is obtained by a "date" before and after.
XXX used to be 16 before the patchset ---> 1st column
--> 16 processes forked as reader
--> + 16 processes forked as writers
--> + 16 msg queues
XXX = 1746 (on my victim) after the patchset ---> last column
--> 1746 reader processes forked
--> + 1746 writers forked
--> + 1746 msg queues created
The same tests on the ref kernel give approximatly the same results.
So if we don't want this longer time to appear as a regression, the LTP
should be changed:
1) either by setting the result of get_max_msgqueues() as the MSGMNI
constant (16) (that would be the best solution in my mind)
2) or by warning the tester that it may take a long time to finish.
There would be 3 tests impacted:
kernel/syscalls/ipc/msgctl/msgctl08.c
kernel/syscalls/ipc/msgctl/msgctl09.c
kernel/syscalls/ipc/msgget/msgget03.c
We will change the test case if need that be. Nadia, kindly send us the
patch set which will do the necessary changes.
Regards--
Subrata
Subrata,
You'll find the patch in attachment.
FYI I didn't change msgget03.c since we need to get the actual max value
in order to generate an error.
Regards,
Nadia
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