Hi,
This optimization is broken. The main concern here: Is it possible that
lru_add_drain_all() _would_ have drained pagevec X, but then aborted
because another lru_add_drain_all() is underway and that other task will
_not_ drain pagevec X? I claim the answer is yes!
My suggested changes are inli
On Mon, May 25, 2020 at 05:24:01PM +0200, Ahmed S. Darwish wrote:
> Peter Zijlstra wrote:
> > On Tue, May 19, 2020 at 11:45:24PM +0200, Ahmed S. Darwish wrote:
> > > + WRITE_ONCE(lru_drain_gen, lru_drain_gen + 1);
> > > + smp_wmb();
> >
> > You can leave this smp_wmb() out and rely on the smp_mb(
Peter Zijlstra wrote:
> On Tue, May 19, 2020 at 11:45:24PM +0200, Ahmed S. Darwish wrote:
> > @@ -713,10 +713,20 @@ static void lru_add_drain_per_cpu(struct work_struct
> > *dummy)
> > */
> > void lru_add_drain_all(void)
> > {
>
Re-adding cut-out comment for context:
/*
* l
On Fri, May 22, 2020 at 05:17:05PM +0200, Sebastian A. Siewior wrote:
> On 2020-05-22 16:57:07 [+0200], Peter Zijlstra wrote:
> > > @@ -725,21 +735,48 @@ void lru_add_drain_all(void)
> > > if (WARN_ON(!mm_percpu_wq))
> > > return;
> > >
> >
> > > + this_gen = READ_ONCE(lru_drain_gen)
On 2020-05-22 16:57:07 [+0200], Peter Zijlstra wrote:
> > @@ -725,21 +735,48 @@ void lru_add_drain_all(void)
> > if (WARN_ON(!mm_percpu_wq))
> > return;
> >
>
> > + this_gen = READ_ONCE(lru_drain_gen);
> > + smp_rmb();
>
> this_gen = smp_load_acquire(&lru_drain_gen);
>
On Tue, May 19, 2020 at 11:45:24PM +0200, Ahmed S. Darwish wrote:
> @@ -713,10 +713,20 @@ static void lru_add_drain_per_cpu(struct work_struct
> *dummy)
> */
> void lru_add_drain_all(void)
> {
> + static unsigned int lru_drain_gen;
> static struct cpumask has_work;
> + static DE
On Wed, May 20, 2020 at 03:22:15PM +0300, Konstantin Khlebnikov wrote:
> On 20/05/2020 00.45, Ahmed S. Darwish wrote:
> > Commit eef1a429f234 ("mm/swap.c: piggyback lru_add_drain_all() calls")
> > implemented an optimization mechanism to exit the to-be-started LRU
> > drain operation (name it A) if
On 20/05/2020 00.45, Ahmed S. Darwish wrote:
Commit eef1a429f234 ("mm/swap.c: piggyback lru_add_drain_all() calls")
implemented an optimization mechanism to exit the to-be-started LRU
drain operation (name it A) if another drain operation *started and
finished* while (A) was blocked on the LRU dr
Commit eef1a429f234 ("mm/swap.c: piggyback lru_add_drain_all() calls")
implemented an optimization mechanism to exit the to-be-started LRU
drain operation (name it A) if another drain operation *started and
finished* while (A) was blocked on the LRU draining mutex.
This was done through a seqcount
9 matches
Mail list logo
