Yafang Shao wrote:
> 2017-11-26 16:03 GMT+08:00 Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>:
> > Yafang Shao wrote:
> >> >> I have also verified your test code on my machine, but can not find
> >> >> this message.
> >> >>
> >> >
> >> > Not always printed. It is timing dependent.
> >> >
> >>
> >> I will try and analysis why this happen.
> >>
> > I see.
> >
> > Here is dump of variables. Always mostly 0 when this happens.
> >
> > --- a/mm/page-writeback.c
> > +++ b/mm/page-writeback.c
> > @@ -434,7 +434,8 @@ static void domain_dirty_limits(struct dirty_throttle_control *dtc)
> > bg_thresh = (bg_ratio * available_memory) / PAGE_SIZE;
> >
> > if (unlikely(bg_thresh >= thresh)) {
> > - pr_warn("vm direct limit must be set greater than background limit.\n");
> > + pr_warn("vm direct limit must be set greater than background limit. bg_thresh=%lu thresh=%lu bg_bytes=%lu bytes=%lu bg_ratio=%lu ratio=%lu gdtc=%p gdtc->vail=%lu vm_dirty_bytes=%lu dirty_background_bytes=%lu\n",
> > + bg_thresh, thresh, bg_bytes, bytes, bg_ratio, ratio, gdtc, gdtc ? gdtc->avail : 0UL, vm_dirty_bytes, dirty_background_bytes);
> > bg_thresh = thresh / 2;
> > }
>
> You could print dtc->avail as well.
> Seems bg_thresh and thresh are not so acurate as they are interger
> other than float.
Indeed, dtc->avail < 4 when this message is printed.
[ 314.730541] vm direct limit must be set greater than background limit. bg_thresh=0 thresh=0 bg_bytes=0 bytes=0 bg_ratio=409 ratio=1228 gdtc= (null) gdtc->avail=0 vm_dirty_bytes=0 dirty_background_bytes=0 dtc->avail=2
[ 315.864111] vm direct limit must be set greater than background limit. bg_thresh=0 thresh=0 bg_bytes=0 bytes=0 bg_ratio=409 ratio=1228 gdtc= (null) gdtc->avail=0 vm_dirty_bytes=0 dirty_background_bytes=0 dtc->avail=1
[ 315.864126] vm direct limit must be set greater than background limit. bg_thresh=0 thresh=0 bg_bytes=0 bytes=0 bg_ratio=409 ratio=1228 gdtc= (null) gdtc->avail=0 vm_dirty_bytes=0 dirty_background_bytes=0 dtc->avail=1
[ 315.993866] vm direct limit must be set greater than background limit. bg_thresh=0 thresh=0 bg_bytes=0 bytes=0 bg_ratio=409 ratio=1228 gdtc= (null) gdtc->avail=0 vm_dirty_bytes=0 dirty_background_bytes=0 dtc->avail=2
[ 355.807392] vm direct limit must be set greater than background limit. bg_thresh=0 thresh=0 bg_bytes=0 bytes=0 bg_ratio=409 ratio=1228 gdtc= (null) gdtc->avail=0 vm_dirty_bytes=0 dirty_background_bytes=0 dtc->avail=2
[ 406.819939] vm direct limit must be set greater than background limit. bg_thresh=0 thresh=0 bg_bytes=0 bytes=0 bg_ratio=409 ratio=1228 gdtc= (null) gdtc->avail=0 vm_dirty_bytes=0 dirty_background_bytes=0 dtc->avail=1
[ 407.782790] vm direct limit must be set greater than background limit. bg_thresh=0 thresh=0 bg_bytes=0 bytes=0 bg_ratio=409 ratio=1228 gdtc= (null) gdtc->avail=0 vm_dirty_bytes=0 dirty_background_bytes=0 dtc->avail=1
[ 416.939906] vm direct limit must be set greater than background limit. bg_thresh=0 thresh=0 bg_bytes=0 bytes=0 bg_ratio=409 ratio=1228 gdtc= (null) gdtc->avail=0 vm_dirty_bytes=0 dirty_background_bytes=0 dtc->avail=1
[ 417.090872] vm direct limit must be set greater than background limit. bg_thresh=0 thresh=0 bg_bytes=0 bytes=0 bg_ratio=409 ratio=1228 gdtc= (null) gdtc->avail=0 vm_dirty_bytes=0 dirty_background_bytes=0 dtc->avail=3
[ 417.093164] vm direct limit must be set greater than background limit. bg_thresh=0 thresh=0 bg_bytes=0 bytes=0 bg_ratio=409 ratio=1228 gdtc= (null) gdtc->avail=0 vm_dirty_bytes=0 dirty_background_bytes=0 dtc->avail=3
[ 417.093176] vm direct limit must be set greater than background limit. bg_thresh=0 thresh=0 bg_bytes=0 bytes=0 bg_ratio=409 ratio=1228 gdtc= (null) gdtc->avail=0 vm_dirty_bytes=0 dirty_background_bytes=0 dtc->avail=3
[ 417.093183] vm direct limit must be set greater than background limit. bg_thresh=0 thresh=0 bg_bytes=0 bytes=0 bg_ratio=409 ratio=1228 gdtc= (null) gdtc->avail=0 vm_dirty_bytes=0 dirty_background_bytes=0 dtc->avail=3
[ 417.093191] vm direct limit must be set greater than background limit. bg_thresh=0 thresh=0 bg_bytes=0 bytes=0 bg_ratio=409 ratio=1228 gdtc= (null) gdtc->avail=0 vm_dirty_bytes=0 dirty_background_bytes=0 dtc->avail=3
[ 417.093198] vm direct limit must be set greater than background limit. bg_thresh=0 thresh=0 bg_bytes=0 bytes=0 bg_ratio=409 ratio=1228 gdtc= (null) gdtc->avail=0 vm_dirty_bytes=0 dirty_background_bytes=0 dtc->avail=3
[ 417.093206] vm direct limit must be set greater than background limit. bg_thresh=0 thresh=0 bg_bytes=0 bytes=0 bg_ratio=409 ratio=1228 gdtc= (null) gdtc->avail=0 vm_dirty_bytes=0 dirty_background_bytes=0 dtc->avail=3
[ 417.093213] vm direct limit must be set greater than background limit. bg_thresh=0 thresh=0 bg_bytes=0 bytes=0 bg_ratio=409 ratio=1228 gdtc= (null) gdtc->avail=0 vm_dirty_bytes=0 dirty_background_bytes=0 dtc->avail=3
[ 417.093223] vm direct limit must be set greater than background limit. bg_thresh=0 thresh=0 bg_bytes=0 bytes=0 bg_ratio=409 ratio=1228 gdtc= (null) gdtc->avail=0 vm_dirty_bytes=0 dirty_background_bytes=0 dtc->avail=3
[ 417.093232] vm direct limit must be set greater than background limit. bg_thresh=0 thresh=0 bg_bytes=0 bytes=0 bg_ratio=409 ratio=1228 gdtc= (null) gdtc->avail=0 vm_dirty_bytes=0 dirty_background_bytes=0 dtc->avail=3
[ 417.093240] vm direct limit must be set greater than background limit. bg_thresh=0 thresh=0 bg_bytes=0 bytes=0 bg_ratio=409 ratio=1228 gdtc= (null) gdtc->avail=0 vm_dirty_bytes=0 dirty_background_bytes=0 dtc->avail=3
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