Messages in this thread | | | From | Geert Uytterhoeven <> | Date | Fri, 21 May 2021 17:38:06 +0200 | Subject | Re: [PATCH] btrfs: scrub: per-device bandwidth control |
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Hi David,
On Fri, May 21, 2021 at 5:18 PM David Sterba <dsterba@suse.cz> wrote: > On Thu, May 20, 2021 at 03:14:03PM +0200, Arnd Bergmann wrote: > > On Thu, May 20, 2021 at 9:43 AM Geert Uytterhoeven <geert@linux-m68k.org> wrote: > > > On Tue, 18 May 2021, David Sterba wrote: > > > > + /* Start new epoch, set deadline */ > > > > + now = ktime_get(); > > > > + if (sctx->throttle_deadline == 0) { > > > > + sctx->throttle_deadline = ktime_add_ms(now, time_slice / div); > > > > > > ERROR: modpost: "__udivdi3" [fs/btrfs/btrfs.ko] undefined! > > > > > > div_u64(bwlimit, div) > > > > If 'time_slice' is in nanoseconds, the best interface to use > > is ktime_divns(). > > It's in miliseconds and the division above is int/int, the problematic > one is below.
Yep, sorry for the wrong pointer.
> > > > > > + sctx->throttle_sent = 0; > > > > + } > > > > + > > > > + /* Still in the time to send? */ > > > > + if (ktime_before(now, sctx->throttle_deadline)) { > > > > + /* If current bio is within the limit, send it */ > > > > + sctx->throttle_sent += sbio->bio->bi_iter.bi_size; > > > > + if (sctx->throttle_sent <= bwlimit / div) > > > > + return; > > > > Doesn't this also need to be changed? > > > > > > + /* We're over the limit, sleep until the rest of the slice */ > > > > + delta = ktime_ms_delta(sctx->throttle_deadline, now); > > > > + } else { > > > > + /* New request after deadline, start new epoch */ > > > > + delta = 0; > > > > + } > > > > + > > > > + if (delta) > > > > + schedule_timeout_interruptible(delta * HZ / 1000); > > > > > > ERROR: modpost: "__divdi3" [fs/btrfs/btrfs.ko] undefined! > > > > > > I'm a bit surprised gcc doesn't emit code for the division by the > > > constant 1000, but emits a call to __divdi3(). So this has to become > > > div_u64(), too. > > > > There is schedule_hrtimeout(), which takes a ktime_t directly > > but has slightly different behavior. There is also an msecs_to_jiffies > > helper that should produce a fast division. > > I'll use msecs_to_jiffies, thanks. If 'hr' in schedule_hrtimeout stands > for high resolution, it's not necessary here.
msecs_to_jiffies() takes (32-bit) "unsigned int", while delta is "s64".
Gr{oetje,eeting}s,
Geert
-- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds
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