Eirik Fuller 880569296f perf test: Handle fd gaps in test__dso_data_reopen
https://github.com/beaker-project/restraint/issues/215 describes a file
descriptor leak which revealed the test failure described here.

The 'DSO data reopen' perf test assumes that RLIMIT_NOFILE limits the
number of open file descriptors, but it actually limits newly opened
file descriptors. When the file descriptor limit is reduced, file
descriptors already open remain open regardless of the new limit. This
test failure does not occur if open file descriptors are contiguous,
beginning at zero.

The following command triggers this perf test failure.

perf test 'DSO data reopen' 3>/dev/null 8>/dev/null

This patch determines the file descriptor limit by opening four files
and then closing them. The limit is set to the fourth file descriptor,
leaving only the first three available because any newly opened file
descriptor must be less than the limit.

Signed-off-by: Eirik Fuller <efuller@redhat.com>
Acked-by: Jiri Olsa <jolsa@redhat.com>
Acked-by: Michael Petlan <mpetlan@redhat.com>
LPU-Reference: 20210626023825.1398547-1-efuller@redhat.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
2021-08-02 10:01:54 -03:00
2021-08-01 17:04:17 -07:00

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.
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