From: Jesper Dangaard Brouer <brouer@redhat.com>
To: Mel Gorman <mgorman@techsingularity.net>
Cc: Chuck Lever <chuck.lever@oracle.com>,
Vlastimil Babka <vbabka@suse.cz>,
Andrew Morton <akpm@linux-foundation.org>,
Christoph Hellwig <hch@infradead.org>,
Alexander Duyck <alexander.duyck@gmail.com>,
Matthew Wilcox <willy@infradead.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>,
brouer@redhat.com
Subject: Re: [PATCH 0/3 v5] Introduce a bulk order-0 page allocator
Date: Tue, 23 Mar 2021 16:08:14 +0100 [thread overview]
Message-ID: <20210323160814.62a248fb@carbon> (raw)
In-Reply-To: <20210323104421.GK3697@techsingularity.net>
On Tue, 23 Mar 2021 10:44:21 +0000
Mel Gorman <mgorman@techsingularity.net> wrote:
> On Mon, Mar 22, 2021 at 09:18:42AM +0000, Mel Gorman wrote:
> > This series is based on top of Matthew Wilcox's series "Rationalise
> > __alloc_pages wrapper" and does not apply to 5.12-rc2. If you want to
> > test and are not using Andrew's tree as a baseline, I suggest using the
> > following git tree
> >
> > git://git.kernel.org/pub/scm/linux/kernel/git/mel/linux.git mm-bulk-rebase-v5r9
> >
>
> Jesper and Chuck, would you mind rebasing on top of the following branch
> please?
>
> git://git.kernel.org/pub/scm/linux/kernel/git/mel/linux.git mm-bulk-rebase-v6r2
>
> The interface is the same so the rebase should be trivial.
>
> Jesper, I'm hoping you see no differences in performance but it's best
> to check.
I will rebase and check again.
The current performance tests that I'm running, I observe that the
compiler layout the code in unfortunate ways, which cause I-cache
performance issues. I wonder if you could integrate below patch with
your patchset? (just squash it)
--
Best regards,
Jesper Dangaard Brouer
MSc.CS, Principal Kernel Engineer at Red Hat
LinkedIn: http://www.linkedin.com/in/brouer
[PATCH] mm: optimize code layout for __alloc_pages_bulk
From: Jesper Dangaard Brouer <brouer@redhat.com>
Looking at perf-report and ASM-code for __alloc_pages_bulk() then the code
activated is suboptimal. The compiler guess wrong and place unlikely code in
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
Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
---
mm/page_alloc.c | 10 +++++-----
1 file changed, 5 insertions(+), 5 deletions(-)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index f60f51a97a7b..88a5c1ce5b87 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -5003,10 +5003,10 @@ int __alloc_pages_bulk(gfp_t gfp, int preferred_nid,
unsigned int alloc_flags;
int nr_populated = 0, prep_index = 0;
- if (WARN_ON_ONCE(nr_pages <= 0))
+ if (unlikely(nr_pages <= 0))
return 0;
- if (WARN_ON_ONCE(page_list && !list_empty(page_list)))
+ if (unlikely(page_list && !list_empty(page_list)))
return 0;
/* Skip populated array elements. */
@@ -5018,7 +5018,7 @@ int __alloc_pages_bulk(gfp_t gfp, int preferred_nid,
prep_index = nr_populated;
}
- if (nr_pages == 1)
+ if (unlikely(nr_pages == 1))
goto failed;
/* May set ALLOC_NOFRAGMENT, fragmentation will return 1 page. */
@@ -5054,7 +5054,7 @@ 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 */
@@ -5075,7 +5075,7 @@ 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:[~2021-03-23 15:08 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-22 9:18 [PATCH 0/3 v5] Introduce a bulk order-0 page allocator Mel Gorman
2021-03-22 9:18 ` [PATCH 1/3] mm/page_alloc: Rename alloced to allocated Mel Gorman
2021-03-22 9:18 ` [PATCH 2/3] mm/page_alloc: Add a bulk page allocator Mel Gorman
2021-03-23 16:00 ` Jesper Dangaard Brouer
2021-03-23 18:43 ` Mel Gorman
2021-03-22 9:18 ` [PATCH 3/3] mm/page_alloc: Add an array-based interface to the " Mel Gorman
2021-03-22 12:04 ` [PATCH 0/3 v5] Introduce a bulk order-0 " Jesper Dangaard Brouer
2021-03-22 16:44 ` Mel Gorman
2021-03-22 18:25 ` Chuck Lever III
2021-03-22 19:49 ` Mel Gorman
2021-03-22 20:32 ` Chuck Lever III
2021-03-22 20:58 ` Mel Gorman
2021-03-23 11:08 ` Jesper Dangaard Brouer
2021-03-23 14:45 ` Mel Gorman
2021-03-23 18:52 ` Chuck Lever III
2021-03-23 11:13 ` Matthew Wilcox
2021-03-23 10:44 ` Mel Gorman
2021-03-23 15:08 ` Jesper Dangaard Brouer [this message]
2021-03-23 16:29 ` Mel Gorman
2021-03-23 17:06 ` Jesper Dangaard Brouer
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