Messages in this thread | | | Date | Mon, 12 Feb 2024 11:13:13 -0800 | From | Yury Norov <> | Subject | Re: [PATCH v3 RESEND 3/6] bitmap: Make bitmap_onto() available to users |
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On Mon, Feb 12, 2024 at 04:36:36PM +0200, Andy Shevchenko wrote: > On Mon, Feb 12, 2024 at 03:20:22PM +0100, Herve Codina wrote: > > On Mon, 12 Feb 2024 16:01:38 +0200 > > Andy Shevchenko <andriy.shevchenko@linux.intel.com> wrote: > > ... > > > Agree, the bitmap_onto() code is simpler to understand than its help. > > > > I introduced bitmap_off() to be the "reverse" bitmap_onto() operations > > and I preferred to avoid duplicating function that do the same things. > > > > On my side, I initially didn't use the bitmap_*() functions and did the the > > bits manipulation by hand. > > During the review, it was suggested to use the bitmap_*() family and I followed > > this suggestion. > > I also would go this way, the problems I see with the current implementation are:
Sure, opencoding and duplicating the functionality is always a bad idea.
> - being related to NUMA (and as Rasmus once pointed out better to be there);
It's 'related to NUMA' for the only reason - it's used by NUMA only. Nothing NUMA-specific in the function itself.
Now that we've got a non-NUMA user, the bitmap_onto() is not related to NUMA anymore.
> - unclear naming, esp. proposed bitmap_off();
That's I agree. Scatter/gather from your last approach sound better. Do you plan to send a v2?
> - the quite hard to understand help text
Yes, we need a picture that would illustrate what actually happens
> - atomicity when it's not needed (AFAICT).
Agree. A series of atomic ops is not atomic. For example
if (test_bit(n, map)) set_bit(m, map);
is not atomic as a whole. And this is what we do in bitmap_onto/off() in a loop. This must be fixed by using underscoded version.
> > I did tests to be sure that bitmap_onto() and bitmap_off() did > > exactly the same things as my previous code did. > > Yuri, what do you think about all this?
I think your scatter/gather is better then this onto/off by naming and implementation. If you'll send a v2, and it would work for Herve, I'd prefer scatter/gather. But we can live with onto/off as well.
Thanks, Yury
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