Re: [PATCH] mem: close rtemap files

[Huzaifa Rahman <huzaifa.rahman@emumba.com>]

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yes, It reduces the opened files from 450 to 2.
Is there any down side of using --single-file-segments flag. Because if
this is better why not make it the default behaviour.

On Thu, Oct 6, 2022 at 3:42 PM Dmitry Kozlyuk <dmitry.kozliuk@gmail.com>
wrote:

> 2022-10-06 10:04 (UTC+0000), huzaifa.rahman:
> > Bugzilla ID: 560
> >
> > The memory subsystem is leaving open a file descriptor for each
> > rtemap file. This can lead to hundreds of extra open file descriptors
> > which has negative side effects. For example, the application may go
> > over its maximum file descriptor limit, or the application may be using
> > limited API's like select that only allow 1024 file descriptors.
> >
> > The EAL memory subsystem does not need to hold the file open.
> > Probably the original intention was to keep the file locked, but that is
> > not necessary. The Linux kernel keeps a reference count on the file,
> > and the mmap counts is a reference and therefore maintains the file
> > as locked.
> >
> > The fix is just to close the file after it is setup.
> >
> > Signed-off-by: huzaifa.rahman <huzaifa.rahman@emumba.com>
> > ---
> >  lib/eal/linux/eal_memalloc.c | 3 +++
> >  1 file changed, 3 insertions(+)
> >
> > diff --git a/lib/eal/linux/eal_memalloc.c b/lib/eal/linux/eal_memalloc.c
> > index f8b1588cae..955c4e4f95 100644
> > --- a/lib/eal/linux/eal_memalloc.c
> > +++ b/lib/eal/linux/eal_memalloc.c
> > @@ -679,6 +679,9 @@ alloc_seg(struct rte_memseg *ms, void *addr, int
> socket_id,
> >
> >       huge_recover_sigbus();
> >
> > +     close(fd);
> > +     fd_list[list_idx].fds[seg_idx] = -1;
> > +
> >       ms->addr = addr;
> >       ms->hugepage_sz = alloc_sz;
> >       ms->len = alloc_sz;
>
> This breaks rte_memseg_get_fd().
> If memfd_create() was used to open the file descriptor,
> there seems no way to reopen it once closed.
>
> --single-file-segments may be used to save FD count,
> does using it solve your issue?
>

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