Messages in this thread | | | Date | Fri, 16 Apr 2010 14:41:52 +0100 | From | John Berthels <> | Subject | Re: PROBLEM + POSS FIX: kernel stack overflow, xfs, many disks, heavy write load, 8k stack, x86-64 |
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Chris Mason wrote: > shrink_zone on my box isn't 500 bytes, but lets try the easy stuff > first. This is against .34, if you have any trouble applying to .32, > just add the word noinline after the word static on the function > definitions. > > This makes shrink_zone disappear from my check_stack.pl output. > Basically I think the compiler is inlining the shrink_active_zone and > shrink_inactive_zone code into shrink_zone.
Hi Chris,
I hadn't seen the followup discussion on lkml until today, but this message:
http://marc.info/?l=linux-mm&m=127122143303771&w=2
allowed me to look at stack usage in our build environment. If I've understood correctly, it seems that a build with gcc-4.4 and gcc-4.3 have very different stack usages for shrink_zone(): 0x88 versus 0x1d8. (details below).
The reason appears to be the -fconserve-stack compilation option specified when using 4.4, since running the cmdline from mm/.vmscan.cmd with gcc-4.4 but *without* -fconserve-stack gives the same result as with 4.3.
According to the discussion when the flag was added, http://www.gossamer-threads.com/lists/linux/kernel/1131612 this flag seems to primarily affects inlining, so I double-checked the noinline patch you sent to the list and discovered that it had been incorrectly applied to the build tree. Correctly applying that patch to mm/vmscan.c (and using gcc-4.3) gives a
sub $0x78,%rsp
line. I'm very sorry that this test or ours wasn't correct and I'm sorry for sending bad info to the list.
We're currently building a kernel with gcc-4.4 and will let you know if it blows the 8k limit or not.
Thanks for your help.
regards,
jb
$ gcc-4.3 --version gcc-4.3 (Ubuntu 4.3.4-5ubuntu1) 4.3.4 $ gcc-4.4 --version gcc-4.4 (Ubuntu 4.4.1-4ubuntu9) 4.4.1
$ make CC=gcc-4.4 mm/vmscan.o $ objdump -d mm/vmscan.o | less +/shrink_zone 0000000000002830 <shrink_zone>: 2830: 55 push %rbp 2831: 48 89 e5 mov %rsp,%rbp 2834: 41 57 push %r15 2836: 41 56 push %r14 2838: 41 55 push %r13 283a: 41 54 push %r12 283c: 53 push %rbx 283d: 48 81 ec 88 00 00 00 sub $0x88,%rsp 2844: e8 00 00 00 00 callq 2849 <shrink_zone+0x19> $ make clean $ make CC=gcc-4.3 mm/vmscan.o $ objdump -d mm/vmscan.o | less +/shrink_zone 0000000000001ca0 <shrink_zone>: 1ca0: 55 push %rbp 1ca1: 48 89 e5 mov %rsp,%rbp 1ca4: 41 57 push %r15 1ca6: 41 56 push %r14 1ca8: 41 55 push %r13 1caa: 41 54 push %r12 1cac: 53 push %rbx 1cad: 48 81 ec d8 01 00 00 sub $0x1d8,%rsp 1cb4: e8 00 00 00 00 callq 1cb9 <shrink_zone+0x19>
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