On Thu, Mar 10, 2011 at 01:30:19PM +0800, Shaohua Li wrote:
> The zone->lru_lock is heavily contented in workload where activate_page()
> is frequently used. We could do batch activate_page() to reduce the lock
> contention. The batched pages will be added into zone list when the pool
> is full or page reclaim is trying to drain them.
>
> For example, in a 4 socket 64 CPU system, create a sparse file and 64 processes,
> processes shared map to the file. Each process read access the whole file and
> then exit. The process exit will do unmap_vmas() and cause a lot of
> activate_page() call. In such workload, we saw about 58% total time reduction
> with below patch. Other workloads with a lot of activate_page also benefits a
> lot too.
>
> Andrew Morton suggested activate_page() and putback_lru_pages() should
> follow the same path to active pages, but this is hard to implement (see commit
> 7a608572a282a). On the other hand, do we really need putback_lru_pages() to
> follow the same path? I tested several FIO/FFSB benchmark (about 20 scripts for
> each benchmark) in 3 machines here from 2 sockets to 4 sockets. My test doesn't
> show anything significant with/without below patch (there is slight difference
> but mostly some noise which we found even without below patch before). Below
> patch basically returns to the same as my first post.
>
> I tested some microbenchmarks:
> case-anon-cow-rand-mt 0.58%
> case-anon-cow-rand -3.30%
> case-anon-cow-seq-mt -0.51%
> case-anon-cow-seq -5.68%
> case-anon-r-rand-mt 0.23%
> case-anon-r-rand 0.81%
> case-anon-r-seq-mt -0.71%
> case-anon-r-seq -1.99%
> case-anon-rx-rand-mt 2.11%
> case-anon-rx-seq-mt 3.46%
> case-anon-w-rand-mt -0.03%
> case-anon-w-rand -0.50%
> case-anon-w-seq-mt -1.08%
> case-anon-w-seq -0.12%
> case-anon-wx-rand-mt -5.02%
> case-anon-wx-seq-mt -1.43%
> case-fork 1.65%
> case-fork-sleep -0.07%
> case-fork-withmem 1.39%
> case-hugetlb -0.59%
> case-lru-file-mmap-read-mt -0.54%
> case-lru-file-mmap-read 0.61%
> case-lru-file-mmap-read-rand -2.24%
> case-lru-file-readonce -0.64%
> case-lru-file-readtwice -11.69%
> case-lru-memcg -1.35%
> case-mmap-pread-rand-mt 1.88%
> case-mmap-pread-rand -15.26%
> case-mmap-pread-seq-mt 0.89%
> case-mmap-pread-seq -69.72%
> case-mmap-xread-rand-mt 0.71%
> case-mmap-xread-seq-mt 0.38%
>
> The most significent are:
> case-lru-file-readtwice -11.69%
> case-mmap-pread-rand -15.26%
> case-mmap-pread-seq -69.72%
>
> which use activate_page a lot. others are basically variations because
> each run has slightly difference.
>
> In UP case, 'size mm/swap.o'
> before the two patches:
> text data bss dec hex filename
> 6466 896 4 7366 1cc6 mm/swap.o
> after the two patches:
> text data bss dec hex filename
> 6343 896 4 7243 1c4b mm/swap.o
>
> Signed-off-by: Shaohua Li <shaohua.li@xxxxxxxxx>
>
> ---
> mm/swap.c | 45 ++++++++++++++++++++++++++++++++++++++++-----
> 1 file changed, 40 insertions(+), 5 deletions(-)
>
> Index: linux/mm/swap.c
> ===================================================================
> --- linux.orig/mm/swap.c 2011-03-09 12:56:09.000000000 +0800
> +++ linux/mm/swap.c 2011-03-09 12:56:46.000000000 +0800
> @@ -272,14 +272,10 @@ static void update_page_reclaim_stat(str
> memcg_reclaim_stat->recent_rotated[file]++;
> }
>
> -/*
> - * FIXME: speed this up?
> - */
> -void activate_page(struct page *page)
> +static void __activate_page(struct page *page, void *arg)
> {
> struct zone *zone = page_zone(page);
>
> - spin_lock_irq(&zone->lru_lock);
> if (PageLRU(page) && !PageActive(page) && !PageUnevictable(page)) {
> int file = page_is_file_cache(page);
> int lru = page_lru_base_type(page);
> @@ -292,8 +288,45 @@ void activate_page(struct page *page)
>
> update_page_reclaim_stat(zone, page, file, 1);
> }
> +}
> +
> +#ifdef CONFIG_SMP
> +static DEFINE_PER_CPU(struct pagevec, activate_page_pvecs);
> +
> +static void activate_page_drain(int cpu)
> +{
> + struct pagevec *pvec = &per_cpu(activate_page_pvecs, cpu);
> +
> + if (pagevec_count(pvec))
> + pagevec_lru_move_fn(pvec, __activate_page, NULL);
> +}
> +
> +void activate_page(struct page *page)
> +{
> + if (PageLRU(page) && !PageActive(page) && !PageUnevictable(page)) {
> + struct pagevec *pvec = &get_cpu_var(activate_page_pvecs);
> +
> + page_cache_get(page);
> + if (!pagevec_add(pvec, page))
> + pagevec_lru_move_fn(pvec, __activate_page, NULL);
> + put_cpu_var(activate_page_pvecs);
> + }
> +}
> +
> +#else
> +static inline void activate_page_drain(int cpu)
> +{
> +}
> +
> +void activate_page(struct page *page)
> +{
> + struct zone *zone = page_zone(page);
> +
> + spin_lock_irq(&zone->lru_lock);
> + __activate_page(page, NULL);
> spin_unlock_irq(&zone->lru_lock);
> }
> +#endif
Why do we need CONFIG_SMP in only activate_page_pvecs?
The per-cpu of activate_page_pvecs consumes lots of memory in UP?
I don't think so. But if it consumes lots of memory, it's a problem
of per-cpu.
I can't understand why we should hanlde activate_page_pvecs specially.
Please, enlighten me.
--
Kind regards,
Minchan Kim
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