On Tue, 15 Dec 2020 12:54:43 +0100 SeongJae Park <sjpark@xxxxxxxxxx> wrote:
> From: SeongJae Park <sjpark@xxxxxxxxx>
>
> In some use cases, users would want to run multiple monitoring context.
> For example, if a user wants a high precision monitoring and dedicating
> multiple CPUs for the job is ok, because DAMON creates one monitoring
> thread per one context, the user can split the monitoring target regions
> into multiple small regions and create one context for each region. Or,
> someone might want to simultaneously monitor different address spaces,
> e.g., both virtual address space and physical address space.
>
> The DAMON's API allows such usage, but 'damon-dbgfs' does not.
> Therefore, only kernel space DAMON users can do multiple contexts
> monitoring.
>
> This commit allows the user space DAMON users to use multiple contexts
> monitoring by introducing two new 'damon-dbgfs' debugfs files,
> 'mk_context' and 'rm_context'. Users can create a new monitoring
> context by writing the desired name of the new context to 'mk_context'.
> Then, a new directory with the name and having the files for setting of
> the context ('attrs', 'target_ids' and 'record') will be created under
> the debugfs directory. Writing the name of the context to remove to
> 'rm_context' will remove the related context and directory.
>
> Signed-off-by: SeongJae Park <sjpark@xxxxxxxxx>
> ---
> mm/damon/dbgfs.c | 213 ++++++++++++++++++++++++++++++++++++++++++++++-
> 1 file changed, 211 insertions(+), 2 deletions(-)
>
> diff --git a/mm/damon/dbgfs.c b/mm/damon/dbgfs.c
> index a1512d3e5afe..46186b057e1a 100644
> --- a/mm/damon/dbgfs.c
> +++ b/mm/damon/dbgfs.c
[...]
> +/*
> + * Remove a context of @name and its debugfs directory.
> + *
> + * This function should be called while holding damon_dbgfs_lock.
> + *
> + * Return 0 on success, negative error code otherwise.
> + */
> +static int dbgfs_rm_context(char *name)
> +{
> + struct dentry *root, *dir, **new_dirs;
> + struct damon_ctx **new_ctxs;
> + int i, j;
> +
> + if (damon_nr_running_ctxs())
> + return -EBUSY;
> +
> + root = dbgfs_dirs[0];
> + if (!root)
> + return -ENOENT;
> +
> + dir = debugfs_lookup(name, root);
> + if (!dir)
> + return -ENOENT;
> +
> + new_dirs = kmalloc_array(dbgfs_nr_ctxs - 1, sizeof(*dbgfs_dirs),
> + GFP_KERNEL);
> + if (!new_dirs)
> + return -ENOMEM;
> +
> + new_ctxs = kmalloc_array(dbgfs_nr_ctxs - 1, sizeof(*dbgfs_ctxs),
> + GFP_KERNEL);
> + if (!new_ctxs) {
> + kfree(new_dirs);
> + return -ENOMEM;
> + }
> +
> + for (i = 0, j = 0; i < dbgfs_nr_ctxs; i++) {
> + if (dbgfs_dirs[i] == dir) {
> + debugfs_remove(dbgfs_dirs[i]);
> + dbgfs_destroy_ctx(dbgfs_ctxs[i]);
In case of virtual address monitoring, dbgfs_destroy_ctx() calls
damon_destroy_ctx() and damon_destroy_ctx() doesn't put the target pids. I
will fix this in the next version.
> + continue;
> + }
> + new_dirs[j] = dbgfs_dirs[i];
> + new_ctxs[j++] = dbgfs_ctxs[i];
> + }
> +
> + kfree(dbgfs_dirs);
> + kfree(dbgfs_ctxs);
> +
> + dbgfs_dirs = new_dirs;
> + dbgfs_ctxs = new_ctxs;
> + dbgfs_nr_ctxs--;
> +
> + return 0;
> +}
Thanks,
SeongJae Park
[...]
