Re: [PATCH 0/6] alloc_tag: introduce IOCTL-based filtering for MAP

[Suren Baghdasaryan]

On Wed, May 6, 2026 at 1:45 AM Hao Ge <hao.ge@xxxxxxxxx> wrote:
>
> Hi Abhishek and Suren
>
>
> On 2026/5/5 07:36, Abhishek Bapat wrote:
> > Currently, memory allocation profiling data is primarily exposed through
> > /proc/allocinfo. While useful for manual inspection, this text-based
> > interface poses challenges for production monitoring and large-scale
> > analysis:
> >
> > 1. Userspace must parse large amounts of text to extract specific
> > fields.
> > 2. To find specific tags, userspace must read the entire dataset,
> > requiring many context switches and high data copying.
> > 3. The kernel currently aggregates per-CPU counters for every allocation
> > size, even those the user intends to filter out immediately.
> >
> > This series introduces a new IOCTL-based binary interface for allocinfo
> > that supports kernel-side filtering. By allowing the user to specify a
> > filter mask, we significantly reduce the work performed in-kernel and
> > the amount of data transferred to userspace.
> >
> > Performance measurements were conducted on an Intel Xeon Platinum 8481C
> > (224 CPUs) with caches dropped before each run.
> >
> > The IOCTL mechanism shows a ~20x performance improvement for
> > filtered queries. The kernel avoids the expensive per-CPU counter
> > aggregation (alloc_tag_read) for any tags that fail the initial string
> > or location filters.
> >
> > Scenario 1: Specific File Filtering (arch/x86/events/rapl.c)
> > 1. Traditional (cat /proc/allocinfo | grep): 22ms (sys)
> > 2. IOCTL Interface: 1ms (sys)
> >
> > Scenario 2: Compound Filtering (Filename + Size)
> > 1. Traditional: (cat ... | grep | awk): 21ms (sys)
> > 2. IOCTL Interface: 1ms (sys)
> >
> > Scenario 3: Size-Based Filtering (min_size = 1MB)
> > 1. Traditional: (cat ... | awk): 21ms (sys)
> > 2. IOCTL Interface: 14ms (sys)
>
> What a coincidence! I was just about to send an email to Suren
>
> asking about plans for upstreaming a filtering tool for /proc/allocinfo,
>
> and then I came across this patchset.
>
> I have been following and using memory allocation profiling since
>
> it was first introduced. It has been very helpful for our memory
>
> analysis by providing clear visibility into allocation data. However,
>
> we have always wanted a tool to efficiently filter this data to get
>
> exactly what we need, so I previously developed a userspace tool [1]
>
> to help with that.
>
> [1] https://lore.kernel.org/all/20250106112103.25401-1-hao.ge@xxxxxxxxx/
>
> So this patchset provides efficient filtering of allocinfo data via ioctl.
>
> Would the next step be to develop a general-purpose tool under
>
> tools/mm that leverages these ioctls instead of parsing /proc/allocinfo
> text output?

Hi Hao,
Sorry for the delay, I was travelling for LSFMM and missed a bunch of emails.
Yes, we are planning to upstream alloctop tool
(https://android-review.googlesource.com/c/platform/system/memory/libmeminfo/+/3431860)
and now with ioctl support it becomes more relevant. Once this
patchset is merged, we will prepare the tool and post the patch.
Thanks,
Suren.


>
> Thanks
>
> Best Regards
>
> Hao
>
> > Abhishek Bapat (5):
> >    alloc_tag: add ioctl filters to /proc/allocinfo
> >    alloc_tag: add size-based filtering to ioctl
> >    alloc_tag: add accuracy based filtering to ioctl
> >    kselftest: alloc_tag: add kselftest for ioctl interface
> >    kselftest: alloc_tag: extend the allocinfo ioctl kselftest
> >
> > Suren Baghdasaryan (1):
> >    alloc_tag: add ioctl to /proc/allocinfo
> >
> >   .../userspace-api/ioctl/ioctl-number.rst      |   2 +
> >   include/linux/codetag.h                       |   1 +
> >   include/uapi/linux/alloc_tag.h                |  87 +++
> >   lib/alloc_tag.c                               | 249 ++++++++-
> >   lib/codetag.c                                 |  11 +
> >   tools/testing/selftests/alloc_tag/Makefile    |   9 +
> >   .../alloc_tag/allocinfo_ioctl_test.c          | 508 ++++++++++++++++++
> >   7 files changed, 865 insertions(+), 2 deletions(-)
> >   create mode 100644 include/uapi/linux/alloc_tag.h
> >   create mode 100644 tools/testing/selftests/alloc_tag/Makefile
> >   create mode 100644 tools/testing/selftests/alloc_tag/allocinfo_ioctl_test.c
> >