Messages in this thread | | | From | Yury Norov <> | Date | Tue, 29 Aug 2023 06:50:08 -0700 | Subject | Re: [PATCH 00/12] bitmap: rework bitmap_{bit,}remap() |
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On Tue, Aug 29, 2023 at 6:39 AM Andy Shevchenko <andriy.shevchenko@linux.intel.com> wrote: > > On Tue, Aug 29, 2023 at 09:33:29AM +0200, Rasmus Villemoes wrote: > > On 28/08/2023 20.43, Yury Norov wrote: > > > This series adds a test, const-time optimizaton and fixes O(N^2) > > > complexity problem for the functions. It's based on discussion in > > > bitmap: optimize bitmap_remap() series [1], but there's much more work > > > here, so I decided to give it a separete run, and don't name it as v2. > > > > > > bitmap_remap() API has just one user in generic code, and few more in > > > drivers, so this may look like an overkill. But the work gives ~10x > > > better performance for a 1000-bit bitmaps, which is typical for nodemasks > > > in major distros like Ubuntu. > > > > Can you find just _one_ project on Debian Code Search or elsewhere that > > actually uses mbind(2), that could possibly ever trigger the use of that > > bitmap_remap stuff? Also, the bitmap may be order 10, but that's just > > because the kitchen sink distros are silly, real machines have nowhere > > near that number of nodes, so even if mbind is used, the bitmaps > > involved will never actually have anything beyond index ~64. > > > > I think this is all total overkill for non-existing problems, and when > > it takes me 20 seconds to find the first bug, I really don't think it's > > worth the churn. I'm not giving a thorough review on the rest of the > > series, nor commenting on followups. > > I posted one patch to replace these APIs with something else, more particular > for GPIO case(s). Have you chance to look at that? With that taking in, I'm > fully agree on the above statement (as we lose the user of this complicated > thingy which is a niche of the NUMA as you mentioned already).
I saw the code in a comment in some thread but not as a separate patch, and AFAIK you said it's a work-in-progress.
Sorry if I missed your submission. Can you please send the patch or point me to the previous submission?
Also, if after your change bitmap_remap would become a NUMA-specific, should protect it with NUMA guards?
Thanks, Yury
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