From: Vlastimil Babka <vbabka@suse.cz>
To: Mel Gorman <mgorman@techsingularity.net>,
Andrew Morton <akpm@linux-foundation.org>
Cc: Chuck Lever <chuck.lever@oracle.com>,
Jesper Dangaard Brouer <brouer@redhat.com>,
Christoph Hellwig <hch@infradead.org>,
Alexander Duyck <alexander.duyck@gmail.com>,
Matthew Wilcox <willy@infradead.org>,
Ilias Apalodimas <ilias.apalodimas@linaro.org>,
LKML <linux-kernel@vger.kernel.org>,
Linux-Net <netdev@vger.kernel.org>, Linux-MM <linux-mm@kvack.org>,
Linux-NFS <linux-nfs@vger.kernel.org>
Subject: Re: [PATCH 4/9] mm/page_alloc: optimize code layout for __alloc_pages_bulk
Date: Mon, 12 Apr 2021 12:41:43 +0200 [thread overview]
Message-ID: <71449835-d4da-657e-b4cf-b077e9636ff7@suse.cz> (raw)
In-Reply-To: <20210325114228.27719-5-mgorman@techsingularity.net>
On 3/25/21 12:42 PM, Mel Gorman wrote:
> From: Jesper Dangaard Brouer <brouer@redhat.com>
>
> Looking at perf-report and ASM-code for __alloc_pages_bulk() it is clear
> that the code activated is suboptimal. The compiler guesses wrong and
> places unlikely code at the beginning. Due to the use of WARN_ON_ONCE()
> macro the UD2 asm instruction is added to the code, which confuse the
> I-cache prefetcher in the CPU.
Hm that's weird, WARN_ON_ONCE() uses unlikely() too, so the UD2 should end up in
the out-of-fast-path part?
But anyway.
> [mgorman: Minor changes and rebasing]
> Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
> Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-By: Vlastimil Babka <vbabka@suse.cz>
> ---
> mm/page_alloc.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index be1e33a4df39..1ec18121268b 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -5001,7 +5001,7 @@ int __alloc_pages_bulk(gfp_t gfp, int preferred_nid,
> unsigned int alloc_flags;
> int nr_populated = 0;
>
> - if (WARN_ON_ONCE(nr_pages <= 0))
> + if (unlikely(nr_pages <= 0))
> return 0;
>
> /*
> @@ -5048,7 +5048,7 @@ int __alloc_pages_bulk(gfp_t gfp, int preferred_nid,
> * If there are no allowed local zones that meets the watermarks then
> * try to allocate a single page and reclaim if necessary.
> */
> - if (!zone)
> + if (unlikely(!zone))
> goto failed;
>
> /* Attempt the batch allocation */
> @@ -5066,7 +5066,7 @@ int __alloc_pages_bulk(gfp_t gfp, int preferred_nid,
>
> page = __rmqueue_pcplist(zone, ac.migratetype, alloc_flags,
> pcp, pcp_list);
> - if (!page) {
> + if (unlikely(!page)) {
> /* Try and get at least one page */
> if (!nr_populated)
> goto failed_irq;
>
next prev parent reply other threads:[~2021-04-12 10:41 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-25 11:42 [PATCH 0/9 v6] Introduce a bulk order-0 page allocator with two in-tree users Mel Gorman
2021-03-25 11:42 ` [PATCH 1/9] mm/page_alloc: Rename alloced to allocated Mel Gorman
2021-03-25 11:59 ` Matthew Wilcox
2021-04-12 10:01 ` Vlastimil Babka
2021-03-25 11:42 ` [PATCH 2/9] mm/page_alloc: Add a bulk page allocator Mel Gorman
2021-03-25 12:05 ` Matthew Wilcox
2021-03-25 12:37 ` Mel Gorman
2021-04-12 10:21 ` Vlastimil Babka
2021-04-12 10:59 ` Mel Gorman
2021-04-12 11:19 ` Mel Gorman
2021-03-25 11:42 ` [PATCH 3/9] mm/page_alloc: Add an array-based interface to the " Mel Gorman
2021-04-12 10:36 ` Vlastimil Babka
2021-03-25 11:42 ` [PATCH 4/9] mm/page_alloc: optimize code layout for __alloc_pages_bulk Mel Gorman
2021-03-25 12:12 ` Matthew Wilcox
2021-03-25 12:40 ` Mel Gorman
2021-04-12 10:41 ` Vlastimil Babka [this message]
2021-03-25 11:42 ` [PATCH 5/9] mm/page_alloc: inline __rmqueue_pcplist Mel Gorman
2021-04-12 10:59 ` Vlastimil Babka
2021-03-25 11:42 ` [PATCH 6/9] SUNRPC: Set rq_page_end differently Mel Gorman
2021-03-25 11:42 ` [PATCH 7/9] SUNRPC: Refresh rq_pages using a bulk page allocator Mel Gorman
2021-03-25 11:42 ` [PATCH 8/9] net: page_pool: refactor dma_map into own function page_pool_dma_map Mel Gorman
2021-03-25 11:42 ` [PATCH 9/9] net: page_pool: use alloc_pages_bulk in refill code path Mel Gorman
2021-03-25 13:33 ` Alexander Lobakin
2021-03-25 12:50 ` [PATCH 0/9 v6] Introduce a bulk order-0 page allocator with two in-tree users Matthew Wilcox
2021-03-25 13:25 ` Mel Gorman
2021-03-25 14:06 ` Uladzislau Rezki
2021-03-25 14:09 ` Matthew Wilcox
2021-03-25 14:13 ` Uladzislau Rezki
2021-03-25 14:26 ` Mel Gorman
2021-03-25 14:46 ` Uladzislau Rezki
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