On Fri, Jul 9, 2010 at 8:04 PM, KOSAKI Motohiro
<kosaki.motohiro@xxxxxxxxxxxxxx> wrote:
>> On Fri, Jul 9, 2010 at 7:13 PM, KOSAKI Motohiro
>> <kosaki.motohiro@xxxxxxxxxxxxxx> wrote:
>> > If number of reclaimable slabs are zero, shrink_icache_memory() and
>> > shrink_dcache_memory() return 0. but strangely shrink_slab() ignore
>> > it and continue meaningless loop iteration.
>> >
>> > This patch fixes it.
>> >
>> > Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
>> > ---
>> > mm/vmscan.c | 5 +++++
>> > 1 files changed, 5 insertions(+), 0 deletions(-)
>> >
>> > diff --git a/mm/vmscan.c b/mm/vmscan.c
>> > index 0f9f624..8f61adb 100644
>> > --- a/mm/vmscan.c
>> > +++ b/mm/vmscan.c
>> > @@ -243,6 +243,11 @@ unsigned long shrink_slab(unsigned long scanned, gfp_t gfp_mask,
>> > int nr_before;
>> >
>> > nr_before = (*shrinker->shrink)(0, gfp_mask);
>> > + /* no slab objects, no more reclaim. */
>> > + if (nr_before == 0) {
>> > + total_scan = 0;
>>
>> Why do you reset totoal_scan to 0?
>
> If shab objects are zero, we don't need more reclaim.
>
>> I don't know exact meaning of shrinker->nr.
>
> similar meaning of reclaim_stat->nr_saved_scan.
> If total_scan can't divide SHRINK_BATCH(128), saving remainder and using at next shrink_slab().
>
>> AFAIU, it can affect next shrinker's total_scan.
>> Isn't it harmful?
>
> No. This loop is
>
> total_scan = shrinker->nr; /* Reset and init total_scan */
> shrinker->nr = 0;
>
> while (total_scan >= SHRINK_BATCH) {
> nr_before = (*shrinker->shrink)(0, gfp_mask);
> /* no slab objects, no more reclaim. */
> if (nr_before == 0) {
> total_scan = 0;
> break;
> }
> shrink_ret = (*shrinker->shrink)(this_scan, gfp_mask);
> if (shrink_ret == -1)
> break;
> if (shrink_ret < nr_before)
> ret += nr_before - shrink_ret;
> total_scan -= this_scan;
> }
>
> shrinker->nr += total_scan; /* save remainder #of-scan */
>
>
I can't understand your point.
old shrink_slab
shrinker->nr += delta; /* Add delta to previous shrinker's remained count */
total_scan = shrinker->nr;
while(total_scan >= SHRINK_BATCH) {
nr_before = shrink(xxx);
total_scan =- this_scan;
}
shrinker->nr += total_scan;
The total_scan can always be the number < SHRINK_BATCH.
So, when next shrinker calcuates loop count, the number can affect.
new shrink_slab
shrinker->nr += delta; /* nr is always zero by your patch */
total_scan = shrinker->nr;
while(total_scan >= SHRINK_BATCH) {
nr_before = shrink(xxx);
if (nr_before == 0) {
total_scan = 0;
break;
}
}
shrinker->nr += 0;
But after your patch, total_scan is always zero. It never affect
next shrinker's loop count.
Am I missing something?
--
Kind regards,
Minchan Kim
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