On Wed, 8 Dec 2021 14:29:40 +0800 Xin Hao xhao@linux.alibaba.com wrote:
Hi Xin,
Hi park:
On 12/1/21 11:04 PM, SeongJae Park wrote:
When wrong scheme action is requested via the debugfs interface, DAMON prints an error message. Because the function returns error code, this is not really needed. Because the code path is triggered by the user specified input, this can result in kernel log mistakenly being messy.
Completely correct, but there will also be a problem that users can’t quickly locate where the problem is,
Especially too many parameters need to be written into the interface.
I think it is necessary to add some debugging methods to help users find the error without polluting the kernel log.
And i have an idea, like this:
in dbgfs, add a last_cmd_stat interface.
# echo "1 2 1 2 1 2 1 2 1 2 100 ..." > schemes # cat last_cmd_stat # wrong action 100In this way, on the one hand, it will not pollute the kernel log, on the other hand, it will help users find the cause of the operation interface error.
Park, how do you think of about this idea, if ok, i will send a patch.
Thank you always for your great suggestions and efforts! BTW, I prefer to be called with my first name ;)
I want DAMON kernel code to be as simple and small as possible, while putting fancy but complicated features for user conveniences in user space tools like DAMO[1]. In other words, I hope the DAMON debugfs interface to be used as an interface for such user space tools, not an interface for human hands.
IMHO, implementing the feature you proposed in the kernel could make the code slightly bigger, while it can easily implemented in user space. I therefore think the feature would be better to be implemented in user space. If you could send a pull request of the feature for DAMO, it would be so great.
[1] https://github.com/awslabs/damo
Thanks, SJ
To avoid the case, this commit removes the message
Fixes: af122dd8f3c0 ("mm/damon/dbgfs: support DAMON-based Operation Schemes") Signed-off-by: SeongJae Park sj@kernel.org
mm/damon/dbgfs.c | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-)
diff --git a/mm/damon/dbgfs.c b/mm/damon/dbgfs.c index 4bf4204444ab..5b628990ae6e 100644 --- a/mm/damon/dbgfs.c +++ b/mm/damon/dbgfs.c @@ -210,10 +210,8 @@ static struct damos **str_to_schemes(const char *str, ssize_t len, &wmarks.low, &parsed); if (ret != 18) break;
if (!damos_action_valid(action)) {pr_err("wrong action %d\n", action);
if (!damos_action_valid(action)) goto fail;
}if (min_sz > max_sz || min_nr_a > max_nr_a || min_age > max_age) goto fail;
-- Best Regards! Xin Hao