Re: [uml-devel] why does index in truncate_inode_pages_range() grows so much ?

["Toralf Förster" <toralf.foerster@gmx.de>]

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On 12/13/2013 11:51 AM, Richard Weinberger wrote:
> On Fri, Dec 13, 2013 at 10:52 AM, Toralf FA?rster <toralf.foerster@gmx.de> wrote:
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>> On 12/11/2013 09:26 PM, Jan Kara wrote:
>>> Thanks! So this works more or less as expected - trinity issued a
>>> read at absurdly high offset so we created pagecache page a that
>>> offset and tried to read data into it. That failed. We left the
>>> page in the pagecache where it was for reclaim to reclaim it when
>>> free pages are needed. Everything works as designed except we could
>>> possibly argue that it's not the most efficient way to use
>>> pages...
>>>
>>> Patch 'vfs: fix a bug when we do some dio reads with append dio
>>> writes' (http://www.spinics.net/lists/linux-fsdevel/msg70899.html)
>>> should actually change the situation and we won't unnecessarily
>>> cache these pages.
>>>
>> confirmed - applied to latest git tree of Linus I helps.
> 
> Good to know! :-)
> 

OTOH - there's seems to be more places for an improvement - now trinity often runs hours
w/o problem (before it runs within a rather short time into such issues).

But today I got another case (I did not patched the source files except the mentioned patch by Jan Kara)
where the trinity call cycles since 2 hours w/o any progress. But fortunately the system is still responsive,
ssh works and I can shutdown that virtual machine smoothly, furthermore all local and remote file systems
can be unounted cleanly - so that patch is a big improvement).


tfoerste@n22 ~/devel/github/bingo $ date; sudo gdb /home/tfoerste/devel/linux/linux 9776 -n -batch -ex 'bt'
Fri Dec 13 13:54:33 CET 2013
find_get_pages (mapping=0x45182810, start=0, nr_pages=14, pages=0x0) at mm/filemap.c:885
885     }
#0  find_get_pages (mapping=0x45182810, start=0, nr_pages=14, pages=0x0) at mm/filemap.c:885
#1  0x080d669a in pagevec_lookup (pvec=0x40607d40, mapping=0x0, start=0, nr_pages=0) at mm/swap.c:937
#2  0x080d6a9a in truncate_inode_pages_range (mapping=0x45182810, lstart=0, lend=-1) at mm/truncate.c:241
#3  0x080d6e3f in truncate_inode_pages (mapping=0x0, lstart=0) at mm/truncate.c:358
#4  0x0818c2d2 in ext4_evict_inode (inode=0x45182758) at fs/ext4/inode.c:228
#5  0x0811b5ff in evict (inode=0x45182758) at fs/inode.c:549
#6  0x0811c0ed in iput_final (inode=<optimized out>) at fs/inode.c:1419
#7  iput (inode=0x45182758) at fs/inode.c:1437
#8  0x08112056 in do_unlinkat (dfd=5, pathname=0x8065d84 <register_lines+276> "") at fs/namei.c:3718
#9  0x081121c5 in SYSC_unlinkat (flag=<optimized out>, pathname=<optimized out>, dfd=<optimized out>) at fs/namei.c:3754
#10 SyS_unlinkat (dfd=5, pathname=134634884, flag=0) at fs/namei.c:3746
#11 0x08062a94 in handle_syscall (r=0x473b59cc) at arch/um/kernel/skas/syscall.c:35
#12 0x080750f5 in handle_trap (local_using_sysemu=<optimized out>, regs=<optimized out>, pid=<optimized out>) at arch/um/os-Linux/skas/process.c:198
#13 userspace (regs=0x473b59cc) at arch/um/os-Linux/skas/process.c:431
#14 0x0805f750 in fork_handler () at arch/um/kernel/process.c:149
#15 0x5a5a5a5a in ?? ()


tfoerste@n22 ~/devel/github/bingo $ date; sudo gdb /home/tfoerste/devel/linux/linux 9776 -n -batch -ex 'bt'
Fri Dec 13 13:54:47 CET 2013
radix_tree_next_chunk (root=0x3f, iter=0x40607cdc, flags=6) at lib/radix-tree.c:773
773                             index &= ~((RADIX_TREE_MAP_SIZE << shift) - 1);
#0  radix_tree_next_chunk (root=0x3f, iter=0x40607cdc, flags=6) at lib/radix-tree.c:773
#1  0x080cc88e in find_get_pages (mapping=0x45182810, start=0, nr_pages=14, pages=0x6) at mm/filemap.c:844
#2  0x080d669a in pagevec_lookup (pvec=0x40607d40, mapping=0x3f, start=63, nr_pages=63) at mm/swap.c:937
#3  0x080d6a9a in truncate_inode_pages_range (mapping=0x45182810, lstart=0, lend=-1) at mm/truncate.c:241
#4  0x080d6e3f in truncate_inode_pages (mapping=0x3f, lstart=25769803839) at mm/truncate.c:358
#5  0x0818c2d2 in ext4_evict_inode (inode=0x45182758) at fs/ext4/inode.c:228
#6  0x0811b5ff in evict (inode=0x45182758) at fs/inode.c:549
#7  0x0811c0ed in iput_final (inode=<optimized out>) at fs/inode.c:1419
#8  iput (inode=0x45182758) at fs/inode.c:1437
#9  0x08112056 in do_unlinkat (dfd=5, pathname=0x8065d84 <register_lines+276> "") at fs/namei.c:3718
#10 0x081121c5 in SYSC_unlinkat (flag=<optimized out>, pathname=<optimized out>, dfd=<optimized out>) at fs/namei.c:3754
#11 SyS_unlinkat (dfd=5, pathname=134634884, flag=0) at fs/namei.c:3746
#12 0x08062a94 in handle_syscall (r=0x473b59cc) at arch/um/kernel/skas/syscall.c:35
#13 0x080750f5 in handle_trap (local_using_sysemu=<optimized out>, regs=<optimized out>, pid=<optimized out>) at arch/um/os-Linux/skas/process.c:198
#14 userspace (regs=0x473b59cc) at arch/um/os-Linux/skas/process.c:431
#15 0x0805f750 in fork_handler () at arch/um/kernel/process.c:149
#16 0x5a5a5a5a in ?? ()


tfoerste@n22 ~/devel/github/bingo $ date; sudo gdb /home/tfoerste/devel/linux/linux 9776 -n -batch -ex 'bt'
Fri Dec 13 13:57:16 CET 2013
radix_tree_next_chunk (root=0x10, iter=0x40607cdc, flags=6) at lib/radix-tree.c:769
769                                     while (++offset < RADIX_TREE_MAP_SIZE) {
#0  radix_tree_next_chunk (root=0x10, iter=0x40607cdc, flags=6) at lib/radix-tree.c:769
#1  0x080cc88e in find_get_pages (mapping=0x45182810, start=0, nr_pages=14, pages=0x6) at mm/filemap.c:844
#2  0x080d669a in pagevec_lookup (pvec=0x40607d40, mapping=0x10, start=16, nr_pages=16) at mm/swap.c:937
#3  0x080d6a9a in truncate_inode_pages_range (mapping=0x45182810, lstart=0, lend=-1) at mm/truncate.c:241
#4  0x080d6e3f in truncate_inode_pages (mapping=0x10, lstart=25769803792) at mm/truncate.c:358
#5  0x0818c2d2 in ext4_evict_inode (inode=0x45182758) at fs/ext4/inode.c:228
#6  0x0811b5ff in evict (inode=0x45182758) at fs/inode.c:549
#7  0x0811c0ed in iput_final (inode=<optimized out>) at fs/inode.c:1419
#8  iput (inode=0x45182758) at fs/inode.c:1437
#9  0x08112056 in do_unlinkat (dfd=5, pathname=0x8065d84 <register_lines+276> "") at fs/namei.c:3718
#10 0x081121c5 in SYSC_unlinkat (flag=<optimized out>, pathname=<optimized out>, dfd=<optimized out>) at fs/namei.c:3754
#11 SyS_unlinkat (dfd=5, pathname=134634884, flag=0) at fs/namei.c:3746
#12 0x08062a94 in handle_syscall (r=0x473b59cc) at arch/um/kernel/skas/syscall.c:35
#13 0x080750f5 in handle_trap (local_using_sysemu=<optimized out>, regs=<optimized out>, pid=<optimized out>) at arch/um/os-Linux/skas/process.c:198
#14 userspace (regs=0x473b59cc) at arch/um/os-Linux/skas/process.c:431
#15 0x0805f750 in fork_handler () at arch/um/kernel/process.c:149
#16 0x5a5a5a5a in ?? ()

- -- 
MfG/Sincerely
Toralf FA?rster
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