Re: [PATCH 1/2] btrfs: set default discard iops_limit to 1000

[Boris Burkov <boris@bur.io>]

On Wed, Apr 05, 2023 at 10:34:49PM +0500, Roman Mamedov wrote:
> On Wed,  5 Apr 2023 09:20:32 -0700
> Boris Burkov <boris@bur.io> wrote:
> 
> > Previously, the default was a relatively conservative 10. This results
> > in a 100ms delay, so with ~300 discards in a commit, it takes the full
> > 30s till the next commit to finish the discards. On a workstation, this
> > results in the disk never going idle, wasting power/battery, etc.
> > 
> > Set the default to 1000, which results in using the smallest possible
> > delay, currently, which is 1ms. This has shown to not pathologically
> > keep the disk busy by the original reporter.
> > 
> > Link: https://lore.kernel.org/linux-btrfs/ZCxKc5ZzP3Np71IC@infradead.org/T/#m6ebdeb475809ed7714b21b8143103fb7e5a966da
> > Signed-off-by: Boris Burkov <boris@bur.io>
> > ---
> >  fs/btrfs/discard.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/fs/btrfs/discard.c b/fs/btrfs/discard.c
> > index 317aeff6c1da..aef789bcff8f 100644
> > --- a/fs/btrfs/discard.c
> > +++ b/fs/btrfs/discard.c
> > @@ -60,7 +60,7 @@
> >  #define BTRFS_DISCARD_TARGET_MSEC	(6 * 60 * 60UL * MSEC_PER_SEC)
> >  #define BTRFS_DISCARD_MIN_DELAY_MSEC	(1UL)
> >  #define BTRFS_DISCARD_MAX_DELAY_MSEC	(1000UL)
> > -#define BTRFS_DISCARD_MAX_IOPS		(10U)
> > +#define BTRFS_DISCARD_MAX_IOPS		(10000U)
> 
> But the patch sets 10000?

Oops. Thanks!

... Just testing the clamping? I did run the code and observe 100ms
delays between workfn runs, for what it's worth, so it "should be fine"
but I'll resend setting it to 1k properly.

> 
> >  
> >  /* Monotonically decreasing minimum length filters after index 0 */
> >  static int discard_minlen[BTRFS_NR_DISCARD_LISTS] = {
> 
> 
> -- 
> With respect,
> Roman