On Tue, Oct 5, 2021 at 1:04 PM Pavel Machek <pavel@xxxxxx> wrote:
Hi!
On Fri 2021-10-01 13:56:57, Suren Baghdasaryan wrote:
While forking a process with high number (64K) of named anonymous vmas theAndroid
overhead caused by strdup() is noticeable. Experiments with ARM64
I still believe you should simply use numbers and do the
numbers->strings mapping in userspace. We should not need to optimize
strdups in kernel...
Here are complications with mapping numbers to strings in the userspace:
Approach 1: hardcode number->string in some header file and let all
tools use that mapping. The issue is that whenever that mapping
changes all the tools that are using it (including 3rd party ones)
have to be rebuilt. This is not really maintainable since we don't
control 3rd party tools and even for the ones we control, it will be a
maintenance issue figuring out which version of the tool used which
header file.
1a) Just put it into a file in /etc... Similar to header file but
easier...
Approach 2: have a centralized facility (a process or a DB)
maintaining number->string mapping. This would require an additional
request to this facility whenever we want to make a number->string
conversion. Moreover, when we want to name a VMA, we would have to
I see it complicates userspace. But that's better than complicating
kernel, and I don't know what limits on strings you plan, but
considering you'll be outputing the strings in /proc... someone is
going to get confused with parsing.
I'm not a fan of complicating kernel but the proposed approach seems
simple enough to me. Again this is subjective, so I can't really have
a good argument here. Maybe, as Andrew suggested, I should keep it
under a separate config so that whoever does not care about this
feature pays no price for it?