Re: [PATCH 2/9] lib/bitmap: implement bitmap_{empty, full} with bitmap_weight_eq()
From: Yury Norov <yury.norov@gmail.com>
Date: 2021-12-15 17:45:49
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kvm, linux-alpha, linux-crypto, linux-mips, linux-perf-users, linux-riscv, linux-s390, lkml
On Wed, Dec 15, 2021 at 12:41 AM David Laight [off-list ref] wrote:
From: Yury Norovquoted
Sent: 14 December 2021 19:43...quoted
I think that for long bitmaps the most time consuming operation is moving data to L1, and for short bitmaps the difference between approaches is barely measurable. But hweght_long on each iteration can't be more effective than the current version. So, I'll drop this patch for v2 and keep things unchanged.Actually do bitmap_full/empty() calls make any sense at all? The result is stale since bitmaps are designed to do locked operations. If you have a lock covering the bitmap then you should be using something that uses non-locked accesses. Rightly or wrongly that isn't the bitmap api.
Are you talking about __{set,clear}_bit()?
include/asm-generic/bitops/non-atomic.h