From: Michal Hocko <mhocko@kernel.org>
To: Minchan Kim <minchan@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
LKML <linux-kernel@vger.kernel.org>,
linux-mm <linux-mm@kvack.org>,
Miguel de Dios <migueldedios@google.com>,
Wei Wang <wvw@google.com>, Johannes Weiner <hannes@cmpxchg.org>,
Mel Gorman <mgorman@techsingularity.net>
Subject: Re: [PATCH] mm: release the spinlock on zap_pte_range
Date: Mon, 29 Jul 2019 09:45:23 +0200 [thread overview]
Message-ID: <20190729074523.GC9330@dhcp22.suse.cz> (raw)
In-Reply-To: <20190729071037.241581-1-minchan@kernel.org>
On Mon 29-07-19 16:10:37, Minchan Kim wrote:
> In our testing(carmera recording), Miguel and Wei found unmap_page_range
> takes above 6ms with preemption disabled easily. When I see that, the
> reason is it holds page table spinlock during entire 512 page operation
> in a PMD. 6.2ms is never trivial for user experince if RT task couldn't
> run in the time because it could make frame drop or glitch audio problem.
Where is the time spent during the tear down? 512 pages doesn't sound
like a lot to tear down. Is it the TLB flushing?
> This patch adds preemption point like coyp_pte_range.
>
> Reported-by: Miguel de Dios <migueldedios@google.com>
> Reported-by: Wei Wang <wvw@google.com>
> Cc: Michal Hocko <mhocko@kernel.org>
> Cc: Johannes Weiner <hannes@cmpxchg.org>
> Cc: Mel Gorman <mgorman@techsingularity.net>
> Signed-off-by: Minchan Kim <minchan@kernel.org>
> ---
> mm/memory.c | 19 ++++++++++++++++---
> 1 file changed, 16 insertions(+), 3 deletions(-)
>
> diff --git a/mm/memory.c b/mm/memory.c
> index 2e796372927fd..bc3e0c5e4f89b 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -1007,6 +1007,7 @@ static unsigned long zap_pte_range(struct mmu_gather *tlb,
> struct zap_details *details)
> {
> struct mm_struct *mm = tlb->mm;
> + int progress = 0;
> int force_flush = 0;
> int rss[NR_MM_COUNTERS];
> spinlock_t *ptl;
> @@ -1022,7 +1023,16 @@ static unsigned long zap_pte_range(struct mmu_gather *tlb,
> flush_tlb_batched_pending(mm);
> arch_enter_lazy_mmu_mode();
> do {
> - pte_t ptent = *pte;
> + pte_t ptent;
> +
> + if (progress >= 32) {
> + progress = 0;
> + if (need_resched())
> + break;
> + }
> + progress += 8;
Why 8?
> +
> + ptent = *pte;
> if (pte_none(ptent))
> continue;
>
> @@ -1123,8 +1133,11 @@ static unsigned long zap_pte_range(struct mmu_gather *tlb,
> if (force_flush) {
> force_flush = 0;
> tlb_flush_mmu(tlb);
> - if (addr != end)
> - goto again;
> + }
> +
> + if (addr != end) {
> + progress = 0;
> + goto again;
> }
>
> return addr;
> --
> 2.22.0.709.g102302147b-goog
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2019-07-29 7:45 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-29 7:10 [PATCH] mm: release the spinlock on zap_pte_range Minchan Kim
2019-07-29 7:45 ` Michal Hocko [this message]
2019-07-29 8:20 ` Minchan Kim
2019-07-29 8:35 ` Michal Hocko
2019-07-30 12:11 ` Minchan Kim
2019-07-30 12:32 ` Michal Hocko
2019-07-30 12:39 ` Minchan Kim
2019-07-30 12:57 ` Michal Hocko
2019-07-31 5:44 ` Minchan Kim
2019-07-31 7:21 ` Michal Hocko
2019-08-06 10:55 ` Minchan Kim
2019-08-09 12:43 ` [RFC PATCH] mm: drop mark_page_access from the unmap path Michal Hocko
2019-08-09 17:57 ` Mel Gorman
2019-08-09 18:34 ` Johannes Weiner
2019-08-12 8:09 ` Michal Hocko
2019-08-12 15:07 ` Johannes Weiner
2019-08-13 10:51 ` Michal Hocko
2019-08-26 12:06 ` Michal Hocko
2019-08-27 16:00 ` Johannes Weiner
2019-08-27 18:41 ` Michal Hocko
2019-07-30 19:42 ` [PATCH] mm: release the spinlock on zap_pte_range Andrew Morton
2019-07-31 6:14 ` Minchan Kim
2019-08-06 7:05 ` [mm] 755d6edc1a: will-it-scale.per_process_ops -4.1% regression kernel test robot
[not found] ` <20190806080415.GG11812@dhcp22.suse.cz>
2019-08-06 11:00 ` Minchan Kim
2019-08-06 11:11 ` Michal Hocko
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