Re: [External] : nfsd: memory leak when client does many file operations

[Benjamin Coddington <bcodding@redhat.com>]

On 26 Mar 2024, at 13:04, Jan Schunk wrote:

> Before I start doing this on my own build I tried it with unmodified linux-image-6.6.13+bpo-amd64 from Debian 12.
> I installed systemtap, linux-headers-6.6.13+bpo-amd64 and linux-image-6.6.13+bpo-amd64-dbg and tried to run stap:
>
> user@deb:~$ sudo stap -v --all-modules kmem_alloc.stp nfsd_file
> WARNING: Kernel function symbol table missing [man warning::symbols]
> Pass 1: parsed user script and 484 library scripts using 110120virt/96896res/7168shr/89800data kb, in 1360usr/1080sys/4963real ms.
> WARNING: cannot find module kernel debuginfo: No DWARF information found [man warning::debuginfo]
> semantic error: resolution failed in DWARF builder
>
> semantic error: while resolving probe point: identifier 'kernel' at kmem_alloc.stp:5:7
>         source: probe kernel.function("kmem_cache_alloc") {
>                       ^
>
> semantic error: no match
>
> Pass 2: analyzed script: 1 probe, 5 functions, 1 embed, 3 globals using 112132virt/100352res/8704shr/91792data kb, in 30usr/30sys/167real ms.
> Pass 2: analysis failed.  [man error::pass2]
> Tip: /usr/share/doc/systemtap/README.Debian should help you get started.
> user@deb:~$
>
> user@deb:~$ grep -E 'CONFIG_DEBUG_INFO|CONFIG_KPROBES|CONFIG_DEBUG_FS|CONFIG_RELAY' /boot/config-6.6.13+bpo-amd64
> CONFIG_RELAY=y
> CONFIG_KPROBES=y
> CONFIG_KPROBES_ON_FTRACE=y
> CONFIG_DEBUG_INFO=y
> # CONFIG_DEBUG_INFO_NONE is not set
> CONFIG_DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT=y
> # CONFIG_DEBUG_INFO_DWARF4 is not set
> # CONFIG_DEBUG_INFO_DWARF5 is not set
> # CONFIG_DEBUG_INFO_REDUCED is not set
> CONFIG_DEBUG_INFO_COMPRESSED_NONE=y
> # CONFIG_DEBUG_INFO_COMPRESSED_ZLIB is not set
> # CONFIG_DEBUG_INFO_SPLIT is not set
> CONFIG_DEBUG_INFO_BTF=y
> CONFIG_DEBUG_INFO_BTF_MODULES=y
> CONFIG_DEBUG_FS=y
> CONFIG_DEBUG_FS_ALLOW_ALL=y
> # CONFIG_DEBUG_FS_DISALLOW_MOUNT is not set
> # CONFIG_DEBUG_FS_ALLOW_NONE is not set
> user@deb:~$
>
> Do I need to enable other options?

You should just need DEBUG_INFO.. maybe stap can't find it?  You can try to add: -r /path/to/the/kernel/build

.. but usually I use this option for a cross-compile.  Usually I don't have to muck around without the debuginfo packages either.  If I don't have them then I'm annotating the kernel directly.

Maybe just a view of what's happening in /proc/slabinfo would be enough..

Ben