Messages in this thread | | | From | Geert Uytterhoeven <> | Date | Thu, 20 May 2021 15:26:29 +0200 | Subject | Re: [PATCH] btrfs: scrub: per-device bandwidth control |
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Hi Arnd,
On Thu, May 20, 2021 at 3:15 PM Arnd Bergmann <arnd@arndb.de> 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: > > > --- a/fs/btrfs/scrub.c > > > +++ b/fs/btrfs/scrub.c > > > @@ -1988,6 +1993,60 @@ static void scrub_page_put(struct scrub_page *spage) > > > } > > > } > > > > > > +/* > > > + * Throttling of IO submission, bandwidth-limit based, the timeslice is 1 > > > + * second. Limit can be set via /sys/fs/UUID/devinfo/devid/scrub_speed_max. > > > + */ > > > +static void scrub_throttle(struct scrub_ctx *sctx) > > > +{ > > > + const int time_slice = 1000; > > > + struct scrub_bio *sbio; > > > + struct btrfs_device *device; > > > + s64 delta; > > > + ktime_t now; > > > + u32 div; > > > + u64 bwlimit; > > > + > > > + sbio = sctx->bios[sctx->curr]; > > > + device = sbio->dev; > > > + bwlimit = READ_ONCE(device->scrub_speed_max); > > > + if (bwlimit == 0) > > > + return; > > > + > > > + /* > > > + * Slice is divided into intervals when the IO is submitted, adjust by > > > + * bwlimit and maximum of 64 intervals. > > > + */ > > > + div = max_t(u32, 1, (u32)(bwlimit / (16 * 1024 * 1024))); > > > + div = min_t(u32, 64, div); > > > + > > > + /* 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().
Actually this one is not a problem...
> > > > + 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?
... but this is.
Sorry. I added the annotation to the wrong line, after devising which code caused the issue from looking at the generated assembly ;-)
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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