On Fri, Apr 18, 2025 at 8:25 AM T.J. Mercier <tjmerc...@google.com> wrote: > > On Thu, Apr 17, 2025 at 1:26 PM Song Liu <s...@kernel.org> wrote: > > > > On Thu, Apr 17, 2025 at 9:05 AM T.J. Mercier <tjmerc...@google.com> wrote: > > > > > > On Wed, Apr 16, 2025 at 9:56 PM Song Liu <s...@kernel.org> wrote: > > > > > > > > On Wed, Apr 16, 2025 at 7:09 PM T.J. Mercier <tjmerc...@google.com> > > > > wrote: > > > > > > > > > > On Wed, Apr 16, 2025 at 6:26 PM Song Liu <s...@kernel.org> wrote: > > > > [...] > > > > > > > > > > > > Here is another rookie question, it appears to me there is a file > > > > > > descriptor > > > > > > associated with each DMA buffer, can we achieve the same goal with > > > > > > a task-file iterator? > > > > > > > > > > That would find almost all of them, but not the kernel-only > > > > > allocations. (kernel_rss in the dmabuf_dump output I attached earlier. > > > > > If there's a leak, it's likely to show up in kernel_rss because some > > > > > driver forgot to release its reference(s).) Also wouldn't that be a > > > > > ton more iterations since we'd have to visit every FD to find the > > > > > small portion that are dmabufs? I'm not actually sure if buffers that > > > > > have been mapped, and then have had their file descriptors closed > > > > > would show up in task_struct->files; if not I think that would mean > > > > > scanning both files and vmas for each task. > > > > > > > > I don't think scanning all FDs to find a small portion of specific FDs > > > > is a real issue. We have a tool that scans all FDs in the system and > > > > only dump data for perf_event FDs. I think it should be easy to > > > > prototype a tool by scanning all files and all vmas. If that turns out > > > > to be very slow, which I highly doubt will be, we can try other > > > > approaches. > > > > > > But this will not find *all* the buffers, and that defeats the purpose > > > of having the iterator. > > > > Do you mean this approach cannot get kernel only allocations? If > > that's the case, we probably do need a separate iterator. I am > > interested in other folks thoughts on this. > > Correct.
I read more into the code, and realized that udmabuf fd is not for the same file here. I guess this also justifies a separate iterator. Thanks, Song
